UNIVERSITY OF FOOD TECHNOLOGIES - PLOVDIV

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THEMATIC AREAS



Viability of lactic acid bacteria in polyphenol-enriched fermented milks

The enrichment of probiotic dairy products with polyphenol extracts from different plant origins is a good approach to enhance the beneficial health effects of functional foods. The purposes of the present study were to evaluate the effect of rose (Rosa damascena Mill.) petals polyphenol extract (RPPE) fortification on the lactic acid production and the viability of Lactobacillus delbrueckii subsp. bulgaricus S19 (Lb. bulgaricus), Lactobacillus rhamnosus YW (Lb. rhamnosus) and Streptococcus thermophilus S13 (S. thermophilus) in fermented milk samples during refrigerated storage. The fermented milk samples with RPPE (samples R1 and R2) and without RPPE (samples K1 and K2) were stored at 4±2°C for 15 days. The results for physicochemical parameters showed a constant decrease in the pH values from 4.35±0.04 to 3.99±0.03 and an increase in the lactic acid concentration from 8.68±0.17 g/L to 11.45±0.26 g/L, respectively. The residual lactose concentration in the controls (K1 and K2) and supplemented samples (R1 and R2) at the end of the refrigerated storage was about 32.0±0.24 g/L. Good survival of probiotic strains of lactic acid bacteria was observed. The results show that on the 15th day of refrigerated storage, the total count of lactic acid bacteria remains high - about 2.8×10^8 CFU/ml. Thus, RPPE could be used as a functional ingredient in fermented milk production.

Authors: Galin Ivanov, Milena Dimitrova-Dicheva, Kiril Mihalev, and Ivelina Ivanova

Evaluation of the quality indicators of traditional Bulgarian artisanal sheep's cheese

The aim of the present study was to evaluate the physical, chemical, and microbiological parameters of artisanal sheep's milk cheese up to one year of its storage. Changes in its composition were observed from the 45th to the 360th day of ripening in clay pots. A 9% increase in dry matter was reported during the ripening period. The water content decreased by 10%, and the titratable acidity decreased more than twice (277 °T). A decrease in the content of oleic fatty acid (C18:1n9c) was observed (from 28.16% on the 45th day to 26.09% on the 360th day of ripening). The content of the palmitic acid (C16:0) also decreased from 30.24% (45th day) to 30.74% (360th day). Changes in the composition of organic acids were also recorded during the ripening period. The lactic acid levels decreased from 27.66% on the 45th day to 8.62% on the 360th day. Microbiological analysis during the ripening period showed that the total microbial status was mainly represented by the total number of lactobacilli (from 1.2*104 - to 1.1*103 at the end of ripening).

Authors: Stanko Stankov, Hafize Fidan, Тatyana Balabanova, Ivayla Dincheva, Salam A. Ibrahim

Study of the effect of treatment with aqueous extracts by oregano and wild basil on raw poultry meat

Study of the effect of treatment with aqueous extracts by oregano and wild basil on raw poultry meat Abstract. The effect of treatment with aqueous antioxidant extracts of oregano (Origanum vulgare L.) and wild basil (Clinopodium vulgare L.) in refrigerated storage of raw poultry meat was studied. Physicochemical analyzes of meat samples were performed - total protein, ash, fat, dry matter, cooking loss and pH value in dynamics. The content of malondialdehyde (MDA) and the protein profile were determined. The microorganisms growth rate in meat during storage at 4° C for a period of 14 days was monitored. After the 7th day, the total number of mesophilic microorganisms in the meat samples increased to 7.00 log cfu/g, which is indicative of decay. A significant increase in pH value was observed after 14 days of storage, but there were no significant changes in total protein content and protein profile. In all meat samples, the amounts of MDA on days 7 and 14 were significantly below the thresholds indicated in the literature. Experimental groups treated with extracts showed lower values for MDA content compared to the control, which is an indication of certain inhibition of lipid oxidation processes in meat.

Authors: Nikolay Dimitrov, Svetla Dyankova, Ayten Solak, Daniela Miteva, Silviya Ivanova

Lipolitic and oxidative changes in acoustically assisted frozen fattened duck liver

The delicate structure of the fattened duck liver requires rapid freezing as quickly as possible. Acoustically assisted freezing meets both the requirement for quick freezing and energy efficiency. For the purpose of the experiment, a fattened duck liver "foie gras" was used. The degree of lipolysis (acid value) and primary (peroxide value) and secondary (2-thiobarbituric acid value) products of lipid oxidization were examined at 2 h post mortem. The oxidative changes were evaluated after conventional (CF) and acoustically assisted freezing (AAF) and at the 6-th and 12-th month of storage at -18 °C. Both time storage and type of freezing affect the degree of lipolysis. The duck liver after AAF had higher degree of lipolysis at the 12-th month of storage at -18 °C. The peroxide value increased almost 2 times in both fattened duck livers (CF and AAF) during the 6 months of storage at -18 °C and stabilizes until the 12-th month. A conclusion was made that the acoustically assisted freezing of the fattened duck liver did not promote higher lipid oxidation compared to the conventional type of freezing.

Authors: Desislava Vlahova-Vangelova, Desislav Balev, Nikolay Kolev, Stefan Dragoev

Comparison of Green Technologies for Valorizing Sugar Beet Leaves (Beta vulgaris L.)

This study is focused on the valorization of sugar beet leaves (Beta vulgaris L.), a prominent by-product wasted during the process of sugar. For doing so, Ultrasound-Assisted Extraction (UAE), Pressurized Liquid Extraction (PLE), and Maceration Extraction (ME) methods were compared by evaluating the extraction yield and the recovery of Total Phenolic Compounds (TPC), Total Flavonoid Content (TFC), individual phenolic profile, DPPH, FRAP, and ABTS. Ethanol and water (70% V/V) were employed as extracting solvents. The TPC for UAE and PLE methods was 4.90±0.083 and 6.46±0.33 (mg GA/mL), respectively, differing significantly (P<0.05) from each other. Moreover, the TFC in the PLE method was the highest with 1.45±0.06 mg QE/mL (P<0.05). The antioxidant activity of extracts was significantly different as the PLE method yielded the highest quantities. Benzoic acid was present only in the PLE extracts, and PLE and ME methods had the highest quantities of syringic acid (0.35±0.00 mg/L) and Pyrogallol (74.80±0.01 mg/L), respectively. However, the extraction yield obtained by the UAE method (19.58±0.33%) had a significant statistical difference from other methods. Therefore, despite the higher TPC and antioxidant activity obtained by the PLE method, it was proved that UAE yields higher polyphenolic compounds with a lower quantity of beet leaves.

Authors: Peyman Ebrahimi, Dasha Mihaylova, and Anna Lante

Influence of Salt Concentration on Microbiological Growth of Kashkaval Cheese

The aim of the present study was to evaluate the influence of NaCl concentration on the development of microflora in Kashkaval cheese produced from cow’s milk. Three cheese samples were obtained - with low (0.7%), medium (1.5%), and standard content of NaCl (3.1%). Microbiological analyzes were performed on the 1st, 15th, 30th, and 45th days after cheese production. It was established that the NaCl content has a significant influence on the activity and development of the microflora in studied samples. It has been observed that the total LAB increased up to 30 days during ripening, after which their concentration decreased. A higher number of LABs characterized samples with 0.7 % and 1.5 % NaCl compared to those containing 3.1 % NaCl. In samples with low salt content, the non-starter microflora such as Psychrotrophic bacteria, yeast, and mold increased more intensively. The data obtained in this study establish that the concentration of NaCl is important for the regulation of activity of microbiological processes during the ripening of the Kashkaval cheese samples.

Authors: ALEXANDER BALABANOV, GALIN IVANOV, BOGDAN GORANOV, MIHAELA IVANOVA, TATYANA BALABANOVA

Effect of sucrose replacement on nutritional parameters and sensory characteristics of the lollipops with isomaltulose

Lollipops are one of the most popular confectionary products among the consumers of all over the world. The main ingredient for their production is crystal sugar (sucrose). Its partial or complete replacement with suitable alternatives and sweeteners leads to change in sensory profile of lollipops and the overall perception by consumers. The use of isomaltulose may be consider as a revolution in confectionary industry due to its characteristics as a functional, digestible, non-cariogenic and just as importantly as a low glycemic disaccharide. The aim of the present study was to evaluate the effect of isomaltulose as a sugar replacement in lollipops on main nutritional parameters and sensory charactereristics as appearance (color and opacity), taste, aroma also the texture attribute perceived in a mouth. Results shown that isomaltulose can affect significantly the sensory and texture profile of the lollipops comparing the control products with sucrose.

Authors: Raina Hadjikinova and Ivanka Petrova

Study of physical and chemical parameters of goat meat for use in the production of children's food

The issue of rational nutrition of children is still extremely relevant and an effective factor ensuring the preservation of life and health of children. Pathological conditions associated with intolerance to certain components of food are increasingly common. When assessing the chemical composition of experimental samples of goat meat (Zaanen, Alpine, Nubian), no abnormal deviations were detected, and all indicators were in the generally accepted contents of this type of animal muscle tissue. Comparative analysis of goat meat samples shows that the fat content is more than 3 times less than that of lamb. The mass fraction of moisture is higher than mutton by 3-5%. Thus, it confirms that goat meat is a more dietary meat raw material in comparison with lamb. The potassium content among the experimental samples is distinguished by the goat meat of the Nubian breed (4125.83±618.87 mg/ kg), which in comparison with the Zaanen (2470.10 ±370.52 mg/kg) is more than 1.5 times greater, and the Alpine breed (1693.22±253.98 mg/kg) is more than 2 times. The concentration of such essential amino acids as tryptophan, leucine, isoleucine, phenylalanine, methionine allows you to cover from 14% to 30.5% of the daily norm.

Authors: Gulzhan Tokysheva, Kadyrzhan Makangali

Microbial growth kinetics as a method to model and predict the development of starter cultures

A comparative study was conducted on the growth rate of lactic acid bacteria involved in starter cultures for the production of lactic acid products. On the basis of the data obtained on the rate of development, it is possible to predict their development as monocultures or as cultures in symbiotic relationship. In order to achieve the set objective, culture of lactic acid microorganisms in a bioreactor was carried out for 24 hours. Data on the rate of development in the different phases represented by the acid formation curve were recorded for the following strains: Lactobacillus delbrueckii subsp. Bulgaricus S22; Streptococcus thermophilus T1; Lactobacillus rhamnosus 1013; Lactobacillus casei shirota. The conclusions drawn allow the correct and predictable use of the investigated strains of lactic acid bacteria in starter cultures for the production of lactic acid products.

Authors: Sergey Sergeev, Bogdan Goranov

Evaluation of the sensory and oxidative properties of fresh sausages with added Agaricus bisporus

The research was conducted to determine the antioxidant effect of mushrooms of the species Agaricus bisporus in fresh sausages, their sensory acceptability and loss during heat treatment. For this purpose, sausages were produced with partial replacement of pork meat with the addition of 10% and 15% blanched mushrooms and fresh sausages with meat replacement with 3% and 6% mushroom flour. With the addition of blanched mushrooms, the most sensory acceptable sausages were obtained, in which the highest mass loss during heat treatment was determined, compared to the sausages with the added mushroom flour, where a lower mass loss during heat treatment was determined, a lower value of the peroxide number, but also lower sensory scores especially for the color, appearance and juiciness of the sausages.

Authors: Tatjana Kalevska, Tanja Stojanovska, Elena Joshevska, Daniela Nikolova Nedelkoska, Sasko Martinovski, Aco Kuzelov

Investigation of edible coatings on the physical, chemical and microbiological characteristics of processed melons during storage

Abstract The possible use of chitosan coating on fresh-cut melons (Сucumis melo var. Cantalupensis) was investigated in this research topic. Manually sliced melons weretreated with solutions of 10 g.kg-1 chitosan and 10 g.kg -1 chitosan with calcium lactate and then stored at 4 °C for 8 days. Physical, physico-chemical, microbiological and sensory properties of the samples were monitored during the storage period. It was found that chitosan coatings inhibited the growth of microorganisms and affected significantly and positively the storage time of the products. Changes in the sensory qualities of taste were evaluated. A chitosan coating retarded water loss and the drop in sensory quality, increasing the soluble solid content and titratable acidity. The data revealed that applying a chitosan coating preserved effectively the quality and extended the shelf-life of fresh-cut melons. Keywords: edible coatings, physical parameters, dielectric parameters, sensory parameters, shelf-life extension Abbreviations: GlcN-β-1,4-linked glucosamine; Mw - average molecular weight; CFU.g-1 - total number of microorganisms; Rm - impedance real part; Xm - impedance imaginary part Acknowledgements: This research was funded by the Agricultural Academy of Bulgaria, project № TN 14: Influence of bioactive edible packaging on the quality of fruits and vegetables during storage (2022-2024) and by Bulgarian National Science Fund (BNSF), grant number KP-06-N37/29". "Innovative packaging, extending the shelf life of fruits and vegetables by multicomponent edible coatings (ECOATFRUIT)".

Authors: Stoil Zhelyazkov, Gabor Zsivanovits, Maria Marudova

Comparative analysis of the degree of hydrolysis and antioxidant activity of milk and whey hydrolysates

The degree of hydrolysis and antioxidant activity of protein hydrolysates from fresh cow's milk and whey obtained by the action of the proteolytic enzymes papain, bromelain and chymosin were compared. The lowest degree of hydrolysis in fresh milk hydrolysates was reported for sample MP1 (10 min reaction time, treatment with 0.1 mg/ml papain), and the highest percentage was obtained at hydrolyzate MB12 (at 60 min reaction time, treatment with 1.0 mg/ml bromelain). For the whey samples in sample WC1 (10 min reaction time, treatment with 1.0 µl/ml chymosin), the percentage of hydrolysis was the lowest. The highest percentage was achieved at WP12 hydrolyzate using papain at a concentration of 1 mg/ml and a 60-min reaction time. The obtained values for the antioxidant capacity of the hydrolyzed products show a higher activity compared to the starting substrates. The highest activity in the milk hydrolysates of 11.32 mg TE/100 ml was found in variant MB3, and in the whey hydrolysates of 7.83 mg TE/100 ml - in variant WP7. Hydrolysates treated with chymosin had lower TE values compared to the hydrolyzates variants, treated with papain and bromelain.

Authors: Alexander Valchkov, Kamelia Loginovska, Maria Doneva, Nadia Ninova-Nikolova, Petya Metodieva

Study of the transfer of some elements important for human health and wine quality in the system bentonite-model medium

Sixteen of the most common bentonites on the Bulgarian market, which are used in Bulgarian wine cellars to achieve colloidal stability of wines, are included in this scientific research. There are bentonites with different composition: sodium, calcium, sodium-calcium, activated calcium, as well as mixtures between natural calcium and activated calcium. By atomic absorption spectrophotometry with inductively coupled plasma (AAS-ICP), their capacity to transfer elements from and to a model medium with wine parameters was investigated. The selected elements which are subject to this study are important for human health as well as for the stability of the wine's clarity.

Authors: Ivan Bakardzhiyski, Elisaveta Mladenova, Silviya Tagareva

Changes in protein profile of beers with bilberry

In the present study, beers with an original extract 12 °P, 14 °P and 16 °P were obtained. During the maturations process, on different stages, bilberries (Vaccinium myrtillus L.) from Bulgaria were added. Changes in the protein profile of the beers were investigated, as well as the influence of these changes on the body in the mouthfeel and the head retention of the resulting beers. The electrophoretic analysis of the proteins was performed by SDS-PAGE. The protein concentration was determined by the Bradford method. The sensory evaluation of the beer’s body and head retention was conducted by a trained five-membered testing panel. It was found that independently of the original extract, the bilberry addition let to a significant reduction of the protein concentration and the number of protein fractions. Beers with bilberry addition contained between 74% and 94% less proteins, than control beers. The number of protein fractions decreased from 10 in the control beers to 4-6 in beers with bilberry. The fractions with molecular weight 14.2 and 31 kDa were the most stable to the bilberry addition. Their part in the beers with bilberry remained the highest. Despite of the significant changes in protein profiles, the beers with bilberry had very good body in the mouthfeel and head retention.

Authors: Petar Nedyalkov, Ivan Bakardzhiyski, Maria Kaneva

Comparative study of volatile substances in spirits beverages distilled by two different initial materials of Prunus domestica “Stanley” in an industrial environment.

Analysis of the chemical composition of volatile substances in two distillates from Prunus domestica “Stanley” cultivated in the village of Rumyantsevo, Lovech, Bulgaria. Production is in an industrial environment, fermentation and distillation are carried out under equal conditions, but on different starting materials. One batch PDS-1 distilled from fermented mash and second batch PDS-2 distilled from fermented juice. The distillation apparatus is equipped with a rectifying column with 4 trays, as well as a water reflux condenser. Determination of congeners in both samples was done by gas chromatography principle OIV-MA-BS-14:2009. Methodology used for measuring alcohol content, cyanide derivatives, furfural and total acidity is according to the requirements of the OIV. In PDS-1 methanol (1094.7 g/hL a.a.) is almost 8% higher than in PDS-2 (1015.8 g/hL a.a.), it was found insignificant increase of furfural content in distillates of PDS-1 than in PDS-2. Concerning esters, aldehydes and higher alcohols the amount in PDS-1 is significantly higher than in PDS-2, respectively 203.06 g/hL, 14.2 g/hL and 484.6 g/hL in batch fermented with hard particles, and 14.2 g/hL, 8.6 g/hL, 267.9 g/hL in batch produced from fermented juice.

Authors: Mariana Al. Galabova, prof. Nikolay Stoyanov, prof. Panko Mitev

Phenolic compounds extractability from Melnik 55 grape solid parts during fruit maturity

Samples from Melnik 55 grape variety (v.vinifera) were collected from different stage of grape maturity. Grape seeds and skins from each sample were separated and extracted with model wine solutions with increasing alcohol content simulated alcohol accumulation during wine fermentation. Total phenolic compounds, anthocyanins, skin pigments and tannins in each sample were determined. During grape ripening not only total phenols content of grape skin and seed is changed but also their extractability. Ethanol released during wine fermentation is strong phenol extragents but its role is getting smaller as more ripe is the grape. This tendency is more pronounced in seeds phenolics extractability than in skins.

Authors: N. Stoyanov, P. Mitev, M. Galabova, S. Tagareva

Application of industrial enzymes in the traditional technology of alcohol from sticky rice in Nam Dinh province, Vietnam

Based on the traditional technology of alcohol from sticky rice in Nam Dinh province, Vietnam, the experiments were conducted by the way to kept the technological process as well as the proportion of ingredients. The quantity of the sticky rice for every experiments was 10 kg. The obtained results showed that the addition of 0.05% enzyme preparation SEBflo-TL compared to the dry matter of sticky rice leads to an increase of the absolute anhydrous alcohol by 10%. Combined application of 0.05% enzyme preparations SEBflo-TL and 0.08% SEBrew-GL for hydrolysing starch and beta glucan, the amount of obtained anhydrous alcohol is 4.6 liters compared to 4.0 liters in the sample control without enzyme application, increased by 15% and could provide significant economic benefits to producer. In other hand, the composition of the volatile compounds of producted alcohol after the first distillation needs to be correced by the fractional distillation to improve quality.

Authors: Tuan Anh Ho, Quang Tu Pham, Thi Hien Dinh, Thi Hanh Vu

Influence of vegetation on the composition of essential oil from (Melissa officinalis L.)

Lemon balm (Melissa officinalis L.) is a perennial plant of the Lamiaceae family, which is used in folk medicine and the food industry, as well as being processed to obtain essential oil. The aim of the special work is to monitor the influence of vegetation on the composition of the essential oil. The chemical composition of essential oils, obtained by steam distillation from balm cultivated in Northeastern Bulgaria, has been determined. The plants were harvested in two periods of vegetation - the first at the end of June and second - at the end of August 2020. The main components in the oil from the first cut are geranial (26.41%), neral (19.55%) ), (E) -β-caryophyllene (17.46%), germacrene D (7.86%) and β-citronellal (3.24%). In the oil from the second cut, the main components are geranial (37.26%), neral (28.46%), (E) β-caryophyllene (6.65%), geraniol (4.72%) and β-citronellal (3 , 04%). The oil from the second harvest has a high content of the main components of geranial, neral and geraniol and a lower content of (E) -β-caryophyllene and germacrene D. Variations in the amounts are also present in other compounds.

Authors: Ivan Iliev, Velko Nedelchev, Vanya Gandova, Albena Stoyanova

Physicochemical parameters of food emulsion products with summer savory (Satureja hortensis L.) essential oil

Summer savory (Satureja hortensis L.) is a plant source of essential oil belonging to the Lamiaceae family, which is widely used in the food industry. The present work aims to determine the physicochemical parameters of food emulsions containing the essential oil of summer savory. The savory essential oil with main components carvacrol (63.71%), γ-terpinene (20.47%), and p-cymene (5.08%) was used in this study. Several model variants of emulsions have been developed with varying amounts of emulsifier (2 and 3% soy protein isolate), oil phase (20 and 40% sunflower oil), and essential oil (0.2 and 0.3%). The following physicochemical parameters of the emulsion were determined: Gibbs free energy (ΔG), kJ mol-1, enthalpy (ΔH), kJ mol-1, and entropy (ΔS), kJ K-1 mol-1. This parameter was used to determine the thermal effect of the system. The process was determined as exothermic with the negative enthalpy. Emulsions prepared with 2% soybean protein isolate, 40% oil phase, and 0.4% essential oil were characterized by some good results with high equilibrium constants and high Gibbs energies. Model variants of salad diet dressings had also been developed, with 0.2 and 0.3% essential oil, which were qualified by sensory analysis. The overall evaluation of salad dressings showed that the evaluators perceived with best sensory properties in those with 0.2% essential oil.

Authors: Anton Lazarov, Stanko Stankov, Hafize Fidan, Vanya Gandova, Albena Stoyanova

Resinoid from Cape Gooseberry Fruit (Physalis peruviana L.) – Volatile Composition and Application as an Active Ingredient in a Cosmetic Formulation

Cape gooseberry (Physalis peruviana L.), an exotic fruit gaining popularity in Bulgaria, has been recognized as a highly functional food, but has also the potential to be a resource for the fragrance and cosmetic industries. The main objective of this study was to assess the potential of the resinoid (a type of traditional aromatic products) obtained from locally-produced fruit (variety “Plovdiv”) for use in cosmetics, by revealing its volatile composition and characterizing the properties of an author-developed resinoid-enriched cosmetic cream. The resinoid (yield 58.78 % DW) was a dark-orange viscous mass, with fruity, caramel notes and smoke accords odor. The GC-MS analysis identified 44 volatiles (98.69%), representing carbohydrates, alcohols, acids, along with minor miscellaneous compounds. A cosmetic cream (O/W emulsion) was developed, incorporating fruit resinoid (1.00%) as an active ingredient, compared to a control sample. Resinoid inclusion affected positively the sensory and physico-chemical properties of the cosmetic cream (color, odor, pH, stability). The studied emulsions had the rheological behavior of pseudoplastic non-Newtonian fluids, and resinoid presence reduced cream viscosity. It could be concluded that Cape gooseberry fruit resinoid had the potential to be a reasonable ingredient in cosmetic preparations; of course, further research is needed to assess its complex effects.

Authors: Nadezhda Mazova, Apostol Simitchiev, Pavel Merdzhanov, Tanya Ivanova, Lazar Lazarov, Venelina Popova

Assessment of Heavy Metal Levels in Roll-Your-Own Cigarette and Water Pipe Tobacco Blends

The increased consumption of roll-your-own (RYO) cigarettes and water pipe (hookah), both globally and in Bulgaria, necessitated the current investigation aimed at the assessment of heavy metal levels in the tobacco blends used in those products. The concentrations of Mn, Zn, Cu, Cd, Pb, and Ni were determined by AAS in five brands of RYO tobacco (R1-R5) and seven brands of water pipe tobacco (W1-W7), all distributed on Bulgarian market. The average heavy metal contents (mg/kg) in the two types of tobacco blends, RYO and water pipe, respectively, were as follows: Mn - 214.20 and 37.89; Zn - 31.90 and 134.87; Cu - 12.06 and 10.07; Cd - 0.80 and 1.33; Pb - 1.60 and 3.57; Ni - 1.36 and 0.80. RYO cigarette tobaccos contained higher concentration of Mn, Cu and Ni, while water pipe tobaccos - Zn, Cd and Pb. Strong correlations were found between Cu and Zn (r=0.81), Cu and Cd (r=0.90) in RYO tobacco blends, and between Cu and Zn (r=0.86) - in water pipe blends, respectively. The results from the study give reason to recommend that this information be provided to the consumers, who consider the regarded tobacco products as a safer alternative to conventional cigarettes.

Authors: Silvia Peeva, Violeta Nikolova, and Nikolay Nikolov, Venelina Popova

Microbiome status of unregulated tobacco blends for hand-rolling cigarettes

The research was conducted on 18 samples of RYO tobacco. The density (CFU/g d. m.) of three heterotrophic groups of microorganisms and some physical-chemical indicators were determined. The analyses were performed according to classical methods. Quantitative and qualitative changes at the microbiome as a result of disruption of homeostasis at microbial communities and development of secondary succession in the direction of intensive mineralization processes were found. Statistically significant correlation dependences with the physical-chemical parameters were registered. In addition to a potential risk in terms of sanitary-hygiene and health aspects, the changes also had a negative impact on the consumer qualities of tobacco blends.

Authors: Tsveta Hristeva, Nikolay Nikolov, Violeta Nikolova, Silvia Peeva



Macro- and trace-element concentrations in green Bulgarian freshwater algae of the genus Spirulina and the genus Chlorella and their suitability for food applications

Macro- and trace-element concentrations in green Bulgarian freshwater algae of the genus Spirulina and the genus Chlorella and their suitability for food applications Nicole Parapanova, Kiril Simitchiev1, Ginka Antova2, Iordanka Alexieva3, Iliana Tomova3, Galya Toncheva4 1Department of Analytical Chemistry and Computer Chemistry, University of Plovdiv, 24 Tsar Assen St., 4000 Plovdiv, Bulgaria 2Department of Chemical Technology, University of Plovdiv, 24 Tsar Assen St., 4000 Plovdiv, Bulgaria 3University of Food Technologies, 24 Boulevard Maritza, 4002 Marasha, Plovdiv, Bulgaria 4Department of General and Inorganic Chemistry, University of Plovdiv, 24 Tsar Assen St., 4000 Plovdiv, Bulgaria Abstract: Element content of freshwater algae species were determined by atomic emission spectrometry (MP-AES) and ICP mass spectrometry after microwave digestion. Cyanobacteria green algae of the genus Spirulina and the genus Chlorella produced in two Bulgarian laboratories were studied. A comparison was made in the drying technique in samples genus Chlorella. Macro and trace element content in dry samples freshwater algae species were 0.6-14.7 mg/g for calcium, 1.2-6.1 mg/g for magnesium, 5.8-10.4 mg/g for potassium, 2.7-16.2 mg/g for sodium, 0.1-0.5 mg/g for iron, 30-258 μg/g for zinc, 6.8-20.9 μg/g for copper, 9.9-101.8 μg/g for manganese, 0.6-3.7 μg/g for nickel. The concentration ranges of some contaminants have also been determined: 0.1-0.14 μg/g for arsenic, 1.6-2.6 μg/g for lead and less than 0.07 μg/g for mercury. While calcium was the highest macro element concentration, manganese was the highest trace element in samples. Most of the analyzed samples were edible. Data on the content of fiber, carbohydrates and proteins in algae and possible limits for use in food products are presented. Keywords: ICP-MS, MP-AES, trace element, freshwater algae Acknowledgements: This work was supported by the Plovdiv University Scientific Fund (grant No SP21-HF-004).

Authors: Macro- and trace-element concentrations in green Bulgarian freshwater algae of the genus Spirulina and the genus Chlorella and their suitability for food applications Nicole Parapanova, Kiril Simitchiev1, Ginka Antova2, Iordanka Alexieva3, Iliana Tomova3, Galya Toncheva4 1Department of Analytical Chemistry and Computer Chemistry, University of Plovdiv, 24 Tsar Assen St., 4000 Plovdiv, Bulgaria 2Department of Chemical Technology, University of Plovdiv, 24 Tsar Assen St., 4000 Plovdiv, Bulgaria 3University of Food Technologies, 24 Boulevard Maritza, 4002 Marasha, Plovdiv, Bulgaria 4Department of General and Inorganic Chemistry, University of Plovdiv, 24 Tsar Assen St., 4000 Plovdiv, Bulgaria

Investigation of probiotic properties of Lactobacillus helveticus 2/20 isolated from rose blossom of Rosa damascena Mill

A lactobacilli strain was isolated from rose blossom of Rosa damascena Mill and it was identified as belonging to the species Lactobacillus helveticus by the application of physiological-biochemical (API 50 CHL) and molecular-genetic methods (sequencing of the 16S rRNA gene). The presence of a number of probiotic properties of L. helveticus 2/20 was investigated. The strain exhibited high antimicrobial activity against pathogenic microorganisms that cause food toxicoinfections and intoxications. L.helveticus 2/20 survived in the simulated conditions of the gastrointestinal tract - pH=2 and pepsin, pH=4.5 and pancreatin and pH=8 and pancreatin, as well as to the presence of 0.3% bile salts, retaining a significant concentration of viable cells. It has been shown that L. helveticus 2/20 cells begin multiplying after removing the extreme conditions. The strain allowed the conduction of industrial cultivation and freeze-drying of the obtained concentrates, with the concentration of active cells in the lyophilic preparations exceeding 1012 cfu/g. The kinetic parameters of the batch cultivation process in a bioreactor with stirring and the maximum growth rate were determined, revealing the possibilities for scaling up the fermentation process from laboratory to industrial conditions, as well as its management. After further research on the probiotic properties of L.helveticus 2/20, it can be included in the composition of probiotics and functional foods.

Authors: R. Denkova-Kostova, B. Goranov, T. Tomova, V. Yanakieva, D. Blazheva, Z. Denkova, G. Kostov

Investigating the growth kinetics of lactobacilli strains with probiotic properties cultivated in a laboratory bioreactor with stirring

Batch cultivation in a laboratory bioreactor with stirring of the lactobacilli strains with probiotic properties Lacticaseibacillus casei ssp. casei G17 and Lacticaseibacillus casei ssp. rhamnosus G16 isolated from pink blossom of Rosa damascena Mill was conducted. The changes in the concentration of viable cells were monitored. The growth kinetics was modeled applying the classic and modified logistic curve model and the maximum specific growth rate of the studied strains was determined. The classical model of the logistic curve showed higher maximum specific growth rate for Lacticaseibacillus casei ssp. casei G17 - 0.133 h-1, compared to Lacticaseibacillus casei ssp. rhamnosus G16 – 0.120 h-1, while the modified logistic curve model predicted comparable maximum growth rates of 0.105-1 and 0.101 h-1 for Lacticaseibacillus casei ssp. casei G17 and Lacticaseibacillus casei ssp. rhamnosus G16, respectively. The induction period and the adaptation rate constant of the strains to the fermentation medium and cultivation conditions were determined. Lacticaseibacillus casei ssp. casei G17 was characterized by a shorter induction period (τa = 0.72 h) and a higher adaptation rate constant (k0 – 0.390 h-1) compared to Lacticaseibacillus casei ssp. rhamnosus G16, in which τa and k0 were 1.66 h and 0.110 h-1, respectively. The established kinetic parameters show that Lacticaseibacillus casei ssp. rhamnosus G16 needs the addition of growth factors in the fermentation medium, that will help to optimize its composition for scaling up the fermentation process.

Authors: B. Goranov, R. Denkova-Kostova, Z. Denkova, G. Kostov

Growth of Gardenia jasminoides shoots in temporally immersion systems and optimization of immersion periods

In the present study, the effect of different immersion regimes on the growth and secondary metabolites production by shoot cultures of Gardenia jasminoides, cultivated in Temporary immersion systems (TIS) was investigated. The cultivation was performed for 30 days on MS medium supplemented with 4.0 mg/l BAP. The investigated regimes were 15 min. immersion on every 4, 8 and 12 hours, respectively. The highest amount of accumulated biomass (ADB = 10.86 ± 0.02 g/L) was reached at 15 min. immersion at every 8 hours, whereas the lowest (ADB = 4.65 ± 0.26 g/L) was recorded when 15 min. immersion on every 4 hours was used. HPLC analyses showed that the higher polyphenol content was achieved when shoots were cultivated by using 15 min. immersion on every 12 hours. At this conditions, the shoots produced maximal amounts of chlorogenic acid (164.82±32.36µg/g DW ), caffeic acid (26,90±6,80µg/g DW), rutin (891,67±122,29µg/g DW) and rosmarinic acid (559,19±19,85µg/g DW). The observed antioxidant activity (DPPH, TEAC, CUPRAC and FRAP) was following the accumulation of polyphenols. The study demonstrates that TIS are effective for cultivation of Gardenia shoots.

Authors: Gergana Krasteva

VALIDATION OF METHOD FOR ANALYSIS OF GLUCOSE IN FOOD ADDITIVES

The dangers of consuming various food and drink products containing substances with a potential risk to human health are the subject of increased interest. There is a drive among manufacturers and the scientific community to ensure safety in the use of various foods and beverages with proven and/or suspected links to one or another disease state. Fast and reliable methods of analysis are increasingly sought for the purpose of establishing the type and concentrations of the contained substances and elements, which methods support the implementation of strict control of the quantitatively regulated levels of various indicators, including main components and impurities. In the present work, a validation procedure of an iodometric method for determining the content of glucose as the main component of three types of nutritional supplements is presented, and results for the analytical characteristics of the method are presented.

Authors: Metodi Mladenov

Characterization of lupine flour and isolated lupine proteins as potential high value food ingredients

Plant proteins have been the subject of research as a potential source of animal protein substitutes for a long time. Lupine belongs to the genus Lupinus and the family Fabaceae and has been used as animal feed until now. In our study, we characterize lupine flour and its derived lupine proteins in terms of chemical composition, antioxidant activity (AOA), and functional properties. The flour possessed 31.46% proteins, 45.11% total dietary fiber, and 7.83 % fats. The results for AOA (DPPH, ABTS, FRAP, and CUPRAC) varied from 1.51 ± 0.09 TE/g sample to 13.10 ± 0.15 TE/g sample. The GC-FID fatty acids analysis revealed that Oleic acid prevailed with 40,55±0,09 %, followed by linoleic acid - 29,1±0,08 %. The proteins of lupin (LPC) were extracted and tested for their functional properties. LPC possessed 3.5 times better foaming capacity. Compared to flour, LPC possessed inferior water holding capacity but much higher oil holding capacity. Both properties were slightly improved by increasing the concentration of NaCl. LPC was less soluble at pH 4.5 and fully soluble at pH 8.0. Again, increasing NaCl concentration to 0.25 M resulted in much better solubility for all pH values tested.

Authors: Aleksandra Garmidolova, Ivelina Desseva, Radka Vrancheva, Atanas Pavlov






Einkorn (Triticum monococcum) and nectarine flour mixture – antioxidant activity, microbiological and sorption characteristics

The current paper presents the initial scientific research on a new enriched flour mixture with nectarine powder comprising physicochemical parameters, antioxidant capacity, microbiological load and sorption characteristics data. The mixture of 70% Einkorn and 30% fruit powder from Bulgarian origin as a functional food supplement was blended. The presence of bioactive components was proved by analysis of antioxidant activity by DPPH, ABTS, FRAP and CUPRAC methods. The microbiological indicators, the total count of mesophilic aerobic and facultative anaerobic microorganisms, molds and yeasts, Escherichia coli, Salmonella spp., coagulase-positive staphylococci and coliforms, were within the permissible norms and no presence of pathogenic microorganisms, were detected in the flour mixture. Adsorption and desorption processes were studied at 10°C, 25°C and 40°C and aw = 0.1÷ 0.9 following static gravimetric methods. The obtained S-shaped equilibrium sorption isotherms confirm the constant trend that with increasing equilibrium moisture content, the temperature decreases in conditions of constant water activity. Based on the obtained sorption capacity data, a calculation of the monolayer moisture content was made using the linearization of the BET model. One of the modified three-parametric models of Oswin, Halsey, Henderson and Chung-Pfost was selected as a suitable model for describing all sorption isotherms.

Authors: Adelina Vasileva, Albena Durakova, Kliment Georgiev, Hristo Kalaydzhiev, Milena Dimitrova-Dicheva and Zhivka Goranova

Degradation of metal ions in waste waters by using Moringa Oleifera seeds

This study outlines the potentialities of metal ions removal from waste waters through the use of Moringa Oleifera seeds as natural coagulant. The tests were conducted with aqueous extracts from powdered seeds at solid-to-liquid ratio of 1:100 g ml-1, coagulant doses from 9 to 51 ml L-1, homogenization for 2 min at rapid mixing speed and 3 min at slow speed. The investigated elements were Cl ions, As, Fe, Cu, Zn, Cd, Pb, Se, Ni, Mn, Co, Bi, Sb, Cr, Mo, F (0.01 ppm to more than 3 ppm). Different samples were taken from the entrance and exit of a sewage treatment plant. The determination of Chlorine and Fluoride was performed by an automatic Mettler Toledo titrator with an electrode 141 SC and Fluoride selective electrode, ICP-OES determined the concentration of heavy metals, all calibrated before use. The removal ability of the bioflocculants varied depending of the type of impurities and dosage used: they decreased effectively the concentration of Cl ions almost proportionally to the amount of extract added, but were effective only for reduction of metal ions with high initial concentration and have no influence of fluoride concentration.

Authors: Nikoleta Stanikina

Investigation of selected independent variables on extrusion of rice semolina with and without propeller

The influence of screws with and without propeller, as well as the independent variables of material moisture, working screw speed, feeding screw speed and die temperature on the changes of some physical and mechanical properties during singles-screw extrusion of rice semolina was studied. The response surface methodology was used with an orthogonal central composite design.

Authors: Yanush Chalamov, Apostol Simitchiev, Ventsislav Nenov, Kiril Vassilev

Performance analysis of bulk food dispensers

The performance of screw dispensers for bulk products - with solid screw and screw spring was investigated. The studied variables are their geometrical parameters, rotation frequency and type of dosed material. The analysis carried out covers a comparison of the objective functions between the two types of dispensers, as well as the assessment of compliance of the real performances with their theoretical models. Conclusions for the specific parameters are summarized.

Authors: Ventsislav Nenov, Donka Stoeva, Stefan Dishliev

Equilibrium isotherms of red beetroot

The equilibrium moisture content of red beetroot has been studied and the corresponding sorption-desorption curves have been obtained at temperature 20°C. The strain measurement method has been used to establish the sorption curves. Analytical dependence describing the sorption and desorption curves have also been derived. Values of equilibrium moisture contents for temperatures higher than 20°C have been obtained by the Pass and Slepchenko’s method. The results are presented in graphical and table form.

Authors: Ivan Kiryakov, Mariya Georgieva, Atanas Tashev, Ivan Tashev

Laboratory convective dryer combined with microwaves

A laboratory convective dryer combined with microwaves has been designed and made. It has been made detailed description of his construction and its working principle. Initial experiments has been conducted to test the dryer when drying root vegetables (parsnips) with combined modes. A few qualitative characteristics of the resulting dried product have been presented - total flavonoids, phenols, etc. An assessment of the energy consumption for the drying process has been made.

Authors: Mariya Georgieva, Dimitar Atanasov, Ivan Kiryakov, Atanas Tashev, Milena Nikolova

Web-based tool for fast qualitative analysis of the sterilization process for foods with extended expiry date

A digital calculator algorithm for F-effect calculation in an online environment is presented. The tool gives a value that analyzes the nature of the sterilization process in thermally processed foods. The obtained result is a reference to "F Soft" software for modelling the process with increasing or decreasing the retention time at reaching the required F-effect, ensuring microbiological stability and nutritional value, while preserving the taste qualities of the canned product in real time mode or when reading external data, creating an appropriate mode. The implementation of the web tool is done with PHP programming language and it provides a quick guideline for the quality of the production cycle of the product to be sterilized.

Authors: Tanya Madzharova, Daniel Hristozov, Elena Mecheva


OpenZFS

Data integrity is crucial in government, business and public sector. Data lost can mean unrecoverable losses of money, reputation or trust. This paper review a storage system based on ZFS (Zettabyte Storage System) that can present the potential of open source file system that provides strong data integrity, simple management, and big capacity.

Authors: Daniel Hristozov

Software tool for data mining of peptides physicochemical properties

Biologically active peptides (BAP) are the subject of increasing research interest because they are successfully used in the medicine, food, and pharmaceutical industries. Investigating the properties of peptides is a laborious and expensive process. Therefore, to discover biological, physicochemical, and sensory properties of peptides, in silico methods, including data mining or artificial intelligence, are increasingly applied. This greatly shortens the process of studying peptide sequences. This paper presents a software tool that uses a data mining approach to discover a number of physicochemical characteristics of a specific peptide. Working with it is extremely simple - it is only necessary to enter the amino acid sequence of the peptide of interest. The software tool is designed to generate data to increase classification and prediction accuracy and also to facilitate the design of new amino acid sequences. In this way, the proposed software will significantly support the work of scientific researchers.

Authors: Zhelyazko Terziyski, Margarita Terziyska, Stanka Hadzhikoleva, Ivelina Desseva



Opportunities for integrated development of rural tourism enterprises, agrariculture, local industry and services in rural areas in the municipality of Mineralni Bani

The purpose of this article is to study and analyze the opportunities of achieving integrated development of rural tourism enterprises, agriculture (agribusiness), industry and services in the municipality of Mineralni Bani. The guest houses and small family hotels serve products produced not only by their owners, but also by other producers in the village. The system of connections and interconnections between the different types of business in Mineralni Bani municipality, built not without the assistance of the municipal leadership, helps to achieve a higher degree of completion of the agricultural and animal products produced in the region (they have a higher added value). This strengthens the demand for these products and increases the tourist flow to the tourist sites in the municipality. In this way, in the municipality of Mineralni Bani, the integration between rural tourism enterprises, individual producers of agricultural products and small processing enterprises gives a strong impetus to the development of the rural area. The strengthening of this integration will lead to results that confirm the positive role and contribution of rural tourism to the stabilization of the economy of the Municipality of Mineralni Bani. In the present study, we used a methodological approach, which is realized through specific methods: the survey and interview method, the method of comparison, synthesis and analysis, etc.

Authors: Associate professor Ivanka Lulcheva







Application of computer-aided molecular modelling approaches for rational development of healthy and safe foods

Application of computer-aided molecular modelling approaches for rational development of healthy and safe foods Merilin Al Sharif1,*, Petko Alov1, Ivanka Tsakovska1, Tania Pencheva1, Ilza Pajeva1 1Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria * merilin.al@biomed.bas.bg Abstract. Background: The increased interest towards biologically active naturally-derived molecules in food/feed industry implies identification of their potential physiologically relevant forms and beneficial/adverse effects. Objective: We aimed at optimization of the systems for quality assessment and evaluation of biological effects of naturally-derived biologically active molecules in healthy foods’ development through in silico approaches. Methods: Analysis of large databases with information on potential targets or hazardous properties of molecules. In silico estimation of potential therapeutic/toxic molecular modes of actions (MoA). Prediction of metabolic transformations. Results: A protocol for virtual screening of triterpenoids relevant to metabolic syndrome alleviation was developed. Possible metabolites and MoA of a triterpenoid found in plants from the genus Astragalus were predicted. An overview of possibilities for data extraction from food/feed safety-relevant databases is presented. Virtual screening of phenols, as promising healthy food components, against the DrugBank database allowed for identification of potential targets of hydroxyanthraquinones found in Rubia spp. and estimation of their potential antibacterial molecular MoA. Conclusions: The developed models reveal potential MoA of the studied biologically active molecules and can support the identification of other naturally-derived molecules as candidates for healthy dietary supplements. Key words: computer-aided molecular modelling, naturally-derived molecules, healthy foods, safe foods. Acknowledgments: This work was supported by the Bulgarian Ministry of Educ

Authors: Merilin Al Sharif, Petko Alov, Ivanka Tsakovska, Tania Pencheva, Ilza Pajeva

PCR analysis for meat products authenticity – detection of horse meat

Food adulteration regarding species origin of meats is a common problem in the meat products sector. With regard to horse meat, its undeclared use in food products is not only a fraud, but could present a health risk since is often associated with the presence of the veterinary drug phenylbutazone in meat products. Therefore, it is important to use reliable methods for authentication of meat products regarding their species composition, which are applicable to complex food matrices. Polymerase chain reaction (PCR) with species-specific primers remains the most widely used analytical approach to detect species-related food adulteration due to its high sensitivity and specificity. The aim of the present study was to establish the authenticity of 20 different meat products on the Bulgarian market without declared horse meat content by using a species-specific PCR method. The specificity test of the PCR method used showed no amplification of DNA from beef and pork. A detection limit of 0.01% horse DNA in three-component meat mixtures was established for the PCR method. The PCR method enabled detection of undeclared presence of horse meat in 25% of the analyzed meat products, which demonstrates the need for strict control regarding authenticity in the meat food chain.

Authors: Petya Stefanova, Velitchka Gotcheva, Angel Angelov

ENHANCING POSTHARVEST QUALITY OF FRESH-CUT PRUNES WITH CHITOSAN-GRAPE SEED OIL EDIBLE COATINGS

Edible coatings are traditionally used to improve food appearance and conservation due to their environmentally friendly nature. In this study fresh cut (halved and pitted) prune (var. Stanley) fruits were coated by chitosan grape-seed-oil (GsO) nanoemulsion. Physical, physico-chemical, microbiological and sensorial properties were examined 3 times during 10 days refrigeration storage. The control probes wasted their safety and quality after the 4th days. The coated probes preserved their quality and safety to the end of the storage period. The fruits with chitosan coating shows smaller microbiological contamination but the chitosan GsO coated fruits shows higher values in the sensorial parameters. Acknowledgements: This research was funded by the Bulgarian Ministry of Education and Science under the National Research Programme "Healthy Foods for a Strong Bio-Economy and Quality of Life" approved by DCM # 577 / 17.08.2018 and by Agricultural Academy of Bulgaria, project № TN 14: Influence of bioactive edible packaging on the quality of fruits and vegetables during storage (2022-2024). The authors say thanks to the Fruit Growing Institute-Plovdiv for providing free fruits for the experiments.

Authors: G. Zsivanovits*, P. Sabeva, D. Iserliyska, S. Zhelyazkov, A. Parzhanova

Edible pH sensitive polysaccharide-anthocyanin complex films for meat freshness monitoring

One of the innovative methods for real-time determination of food freshness is the application of pH-indicator sensors, where the color change can be used for the visual detection of acidic/basic volatile compounds formed during product storage due to microbial growth. The aim of the present study is to develop a pH-responsive freshness indicator based on anthocyanins from chokeberry and black carrot, incorporated into an alginate/pectin/Arabic gum composite film. The resulting films show distinct color changes as the pH varies. In general, the color changes from red (pH 2.0 and 3.0) through pink and pale pink (pH 4.0, 5.0 and 6.0) to purple and blue (pH 7.0 and 8.0). The most distinct is the color transition between pH 6.0 and 7.0 for the black carrot extract and the aronia:black carrot mixture (1:3).The applicability of the developed pH-indicator films was demonstrated in fresh chicken meat by tracking the changes during its storage at 4℃ for 7 days. The observed results show a distinct color change from pink (day 1-3) to violet and blue on day 7. The developed pH-sensitive films have potential for use in a smart packaging system as a sensor for meat freshness monitoring.

Authors: Ayten Solak, Svetla Dyankova, Maria Doneva, Milena Pavlova

Cheese quality assessment by use of near-infrared spectroscopy

Dairy products are worldwide spread and have great commercial importance. Rapid and reliable analysis of cheese would be highly desirable both for the manufacturers and consumers. The results of experiments, related to the application of near-infrared spectroscopy for cheese quality estimation will be presented. Several kinds of Bulgarian white brine cheese - natural from cow milk, imitation products with vegetable oil, and cheese with different water content were investigated. Fatty acids composition of samples was determined by using gas chromatography and moisture content by the oven-dry method. Spectra of all tested samples were obtained with a scanning NIRQuest 512 (Ocean Optics, Inc.) instrument in the range of 900-1700 nm using a reflection fiber-optics probe. PLS models were developed for quantitative determination and SIMCA for classification. The misclassification rate of the SIMCA model for discrimination of natural cheese and imitation products with vegetable oil was 2.9%. Quantitative determination of water content based on NIR spectra showed high accuracy, Models for classification of cheese samples into 3 groups according to water content achieved a 5.64% misclassification rate for the independent test set. Results showed the potential of near-infrared spectroscopy as a non-destructive and rapid screening tool for assessing cheese quality and detecting adulteration.

Authors: Stefka Atanassova, Dimitar Yorgov, Petya Veleva, Todor Stoyanchev, and Zlatin Zlatev

INFLUENCE OF UNREGULATED STORAGE CONDITIONS ON PHYSICOCHEMICAL, ORGANOLEPTIC AND NIR SPECTRAL CHARACTERISTICS OF YELLOW CHEESE

In the present work, software and hardware tools are proposed for determining the change in the main characteristics of Bulgarian yellow cheese during storage in conditions not regulated by the manufacturers. NIR images in the 800-1100 nm range of yellow cheese samples from 3 manufacturers were obtained using a GT-903 video camera with the IR-filter removed from the camera lens. Several physicochemical characteristics of the product were determined - active acidity, electrical conductivity, and completely dissolved solids. Data from the organoleptic evaluation of the product are presented. Using ABC-XYZ analysis, informative wavelengths are selected from the spectral features. Spectral indices calculated as ratios of the reflectance coefficients of selected wavelengths were defined and used to predict the storage characteristics of cheese. It has been found that the shelf life of cheese can be predicted with an accuracy of up to 95%, and the active acidity with an accuracy of up to 88%, depending on the manufacturer. The obtained results can be used for analyzes of cheese during its storage and applied in automatic measurement and control systems, as well as in advisory systems for evaluating the quality of cheese in the different stages of its production, transport, and storage.

Authors: Stanka Baycheva, Zlatin Zlatev, Petya Veleva, Dimitar Yorgov, Stefka Atanasova

Investigation of the influence of particle size and storage period on the moisture of granular synbiotic products – a statistical approach

This article examines the influence of particle size and storage time on the moisture of granular lyophilized synbiotic products - "LYO - Milk Strawberry" and "LYO - Milk Chokeberry". For each of these two products, four variants of mixtures with different types and concentrations of substances (sucrose, locust bean gum, and fructooligosaccharides (FOS)) are prepared. The analysis is based entirely on statistical methods and techniques. The obtained results show that the two factors - particle size and storage time do not have a mutual influence on the moisture of the tested products. However, they have a significant impact individually. It was also found that particle size is directly dependent on the type and concentration of the added substances.

Authors: Margarita Terziyska, Maria Doneva, Petya Metodieva, Iliana Nacheva