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The aim of this research was to study the effects of whey protein concentrate (WPC) and casein hydrolysate (CH) on chemical (pH and titratable acidity), physical (consistency and syneresis) and sensory properties of yogurt containing probiotic bacteria. Reconstituted skim milk at 10% total solids was fortified with 1 and 2% of WPC, CH and blend of them (WPC to CH ratios of 1:1). Reconstituted skim milks were made with 11 and 12% total solids as control. Bioyogurts were prepared with commercial probiotic starter culture (Lactobacillus acidophilus, Bifidobacterium sp., Streptococcus thermophilus and Lactobacillus delbrueckii ssp. bulgaricus). Fermentation was stopped at pH=4.6 and samples stored at 4°C for 21 days. Addition of WPC resulted in the highest pH value and the lowest titratable acidity. Acidity values of supplemented bioyogurt samples increased between 0.12 - 0.19% during 21 days of storage. Mَoreovere syneresis of these yogurts was lower and their consistency was higher than control. Bioyogurts containing WPC had the lowest syneresis and samples containing CH or WPC had the highest consistency. With regards to total acceptability, the best samples were bioyogurts supplemented with WPC and blend of WPC and CH.

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The aim of this research was to study the effects of whey protein concentrate (WPC) and casein hydrolysate (CH) on chemical (pH and titratable acidity), physical (consistency and syneresis) and sensory properties of yogurt. Reconstituted skim milk at 10% total solids was fortified with 1 and 2% of WPC, CH and blend of them (WPC to CH ratios of 1:1). For comparison, reconstituted skim milks were made with 11 and 12% total solids as control. Yogurts were prepared with commercial starter culture (Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus) and their fermentation proccess were stopped at pH=4.6 and samples stored at 4°C up to 21 days. The lowest pH value was obtained when milk base was supplemented with WPC. pH values of all yogurt samples did not change significantly during 21 days of storage and ~0.18% increase in titratable acidity was observed during storage period. The lowest syneresis was observed in yogurts containing blend of WPC and CH. Moreover, the syneresis values of these yogurts increased slower than other samples during storage. Consistency of fortified yogurts was higher than control yogurt and the consistency values of these samples reduced slower than control sample during 21 days of storage. With regards to total acceptability, the best samples were yogurts supplemented with blend of WPC and CH.

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  The goal of this study was to determine the changes of diacetyl content and sensory charactristics  of  yoghurt fortified with whey protein concentrate instead of skim milk powder at storage condition. Our finding showed that with increasing in amount of whey protein concentrate in yoghurt samples, diacetyl level was always higher than control sample. Diacetyl amounts also in yoghurt samples increased during two weeks. The results of sensory evalution also showes  that there was no difference in flavour between control sample and sample C but quality characteristics (flavour, general acceptance) other samples were different from control sample. Results indicated that during storage period quality characteristics, especially improving consistency , creamy texture and more flavouring compounds produced acceptance sample C were close to control sample.  

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The effect of edible whey protein coating and dill (Anethum graveolens) essential oil on the quality and shelf-life of silver carp’s fillets, Hypophthalmichthys molitrix,during refrigeration storage was evaluated. Fillets were immersed in whey protein solution (10%), dill essential oil (5%) and a mixture of whey protein (10%) and dill essential oil (5%), then packed and stored in refrigerator (4˚C). Chemical (PV, TBA and TVB-N) and microbial (TVC and PTC) parameters were measured at 0, 3, 6, 9, 12, 15 and 18 days. The amount of peroxide value and thiobarbitoric acid significantly increased (P < 0.05) in all treatments, but this increace was lower in whey protein coating with dill essential oil fillets. Total volatile basic nitrogen of dill essential oil, whey protein and whey protein with dill essential oil treatments in the first and last phase of storage were 7.55, 7.60, and 7.51- 24.11, 25.84 and 15.55 mgN₂/100 g fillet, respectively. The TVC and PTC amount for whey protein with dill essential oil was lower in comparsion with other treatments. Thus, whey protein coating with dill essential oil increased the shelf-life ofsilver carp’s fillets during refrigerated storage. 

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  The aim of this work was to study the effect of adding gellan gum and glycerol to film-forming solution on physical and mechanical properties of whey protein/gellan gum emulsion films and to produce edible coatings from whey and gellan gum and determine its effect on storage life of apricot. Whey protein coatings were prepared by dispersing 10% protein in distilled water; and plasticized with glycerol(Gly). Also gellan gum was added at different levels(0, 0/2, 0/4 and 0/6gr). Therefore apricots were dipped in this coatings solution for 1 minute at 20˚C and air dried. Coated fruits together with the uncoated fruits(control) were placed in open dishes and stored at 4˚C and 85% RH for 1 months. Weight loss, total soluble solid(TSS), titrable acidity, pH, skin color, flesh firmness and overall acceptability of coated apricots and control were measured weekly.  The result revealed that the weight loss and changes in the quality parameters were much lower in coated apricots as compared with those. Color changes were also studied using a Hunter lab colorimeter. Finally results showed that the applications of whey coating increased overall acceptability, quality and storage life of apricot, while decreased its weight loss during storage. The emulsion films were evaluated for physical and mechanical properties. Increasing the level of gellan gum in the films led to increase in Modulus(EM) and Tensile Strength(TS) but increasing gum to 0/6gr made less increase in Modulus(EM) and Tensile Strength(TS). About Elongation(EL), was observed increase too but in films that produced with 0/4gr gum, there was a slight decrease.

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In this study, physicochemical properties, sensory characteristics and shelf life of muffin prepared by substitution of egg white with different levels of whey protein concentrate (WPC) were evaluated. WPC at three levels – 25, 50 and 75 %– was considered as variable treatment. Physicochemical properties including butter pH, butter consistency, cake pH, weight loss, density, moisture, shelf life properties including water activity () and hardness after 1, 2 and 10 days storage and sensory properties including crust color, taste, texture and total acceptance were measured and the result were analyzed. Data analysis showed that WPC substitution levels affected all of properties.  In comparison with control butter pH, cake pH, moisture, density,   and hardness after 1, 2 and 10 days storage decreased whereas consistency and weight loss increased with increase of substitution level. Also WPC substitution levels affected all of sensory properties. Color score increased with 25 and 50 % WPC but decreased with 75% WPC. Texture, taste and total acceptance scores decreased with increase of substitution. No significant difference of taste and total acceptance scores with control up to 50 % replacement level was noticed; however it became significant at 75% replacement level.  

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Antimicrobial packaging is a form of active packaging that could extend the shelf-life of foods and provides microbial safety for consumers. In order to control undesirable microorganisms on food surfaces, volatile and non-volatile antimicrobial agents can be incorporated into polymers. Incorporation of essential oils and other antifungal agents in edible films composition is an antimicrobial packaging that able to inhibit fungal growth on the pistachio and aflatoxins production. The antifungal activity of Sage (Salvia officinalis) extracts against Aspergillus flavus in whey protein concentrate-based coating on pistachio kernels was investigated. The antifungal effect of Sage extracts was investigated in culture media by direct method (well method) and application of whey protein concentrate (WPC) films as discs (disc method) incorporated with different concentrations of extracts. In order to evaluate the antifungal effect of extract in pistachio, kernels coated with different concentrations of extract inoculated with a culture media discs contain 9-day-old growing A. flavus colony and the growth rate of inoculated discs were measured during 1 week. In experimental condition, minimal inhibition concentration was achieved by 155 ppm of ahcoholic extract (30 percent concentration). The results also showed that WPC coating incorporated with 4000 ppm of Salvia officinalis extracts on pistachio kernels inhibited A. flavus growth totally. Paying regard to economical aspects of importance of contamination with toxigenic fungi in pistachio kernel suggest the application of Sage extract incorporated in edible coatings for toxigenic fungi growth and toxin production in foods.   

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Supplying fresh fish and sea products is accompanied with the problem of their rapid spoilage and short shelf life. Therefore, solutions which help increase this shelf life have always been valued. Accordingly, the aim of this study was to evaluate the effect of whey protein coatings containing four different concentrations (100,200,400 and 800 IU/gr) of nisin in perch fillet for storage in refrigerator temperature. Humidity tests, Peroxide Value, Thiobarbituric acid Index, microbial load, water activity and pH were performed over coated and uncoated samples. The results indicated that increasing the shelf life in all treatments led to an increase in peroxide value, Thiobarbituric acid Index, the load of bacteria, pH and water activity, this increase was less in coated samples than the uncoated ones. On the other hand, the findings showed that whey protein and nisin coating with the of concentration 400 IU/gr of perch fillet can add 16 days to increase the shelf life in refrigerator temperature in comparison with the uncoated samples. Based on our findings, it can be concluded that using whey protein coating containing nisin with the concentration of 400 IU/gr of perch fillet as edible coating  can increase the shelf life in the refrigerator temperature.

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Yog-ice cream (frozen yogurt), is a kind of frozen desserts which has similar features with ice cream in physical and apparent characteristics. In this study, frozen yogurt was produced as a synbiotic product containing both probiotics and prebiotics. Lactobacillus Casei(LAFTI-L26)as a probiotic bacteria was added to low fat frozen yogurt in two types;free and encapsulated,and its survivability was evaluated during 30 days storage at -18^oc.Prebiotic compound that was used in this study,was Inulin that added to frozen yogurt in different levels(0,2.5 and 5% w/w). The viable cell number of L.casei in the free state in prepared low fat frozen yogurt mixture, was between 9.801-9.779 log cfu/ml at the first day, and after 30 days storage at -18^oc,its viable number redused to 7.451-7.866 log cfu/ml. In samples of frozen yogurt containing L.casei that was encapsulated by sodium alginate-whey protein concentration(wpc),the viable cell number of L.casei was 8.150-8.661 log cfu/ml  at the first day that reduced to 6.650-7.477 log cfu/ml at the end of 30 days storage at -18^oc.Totally ,obtained results showed that encapsulation of lactobacillus casei in Alginate-Whey protein capsules, could significantly improve survivability of L.casei.(p<0.05) that the viable number of this bacteria in frozen yogurt containing encapsulated probiotic,was in the range of investigated levels by the International Dairy Federation(10⁶-10⁷ cfu/g).

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Studies on the production of protein supplements for phenylketonuria (PKU) patients indicate that whey protein is one of the most important protein sources for production of these compounds, owning to its specific combination of amino acids.Whey is considered as one of the most polluting by-product in environment, otherwise, it is an excellent source of functional proteins that can be used in medicine and special diet products. In this study, three different concentrations of whey protein concentrate (WPC) were used as a substrate for three enzymes Flavourzyme^®, Neutrase^®and Protamex^®. Effect of substrate concentration and hydrolysis time were studied on the separation efficiency of phenylalanine using response surface methodology (RSM) design. Phenylalanine was removed from hydrolyzed samples using ultra filtration (UF) and its concentration was measured using HPLC technique. Results of this study showed that samples hydrolyzed by Flavourzyme^® contain the lowest level of phenylalanine. Also, process optimization was done in order to predict the best conditions of hydrolyzing .The best condition in order to remove the maximum phenylalanine from whey proteins was found for the minimum hydrolyzing time and the lowest substrate concentration for all three enzymes.

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The purpose of this study was to investigate the effect of lyophilized Alyssum homolocarpum seed gum–whey protein concentrate (with the ratio of 1:1, 1:3 and 3:1) on physicochemical properties of corn oil–in–water emulsions. Interfacial tension and emulsion characteristics such as particle size distribution, zeta potential, flow behavior, viscosity and creaming were investigated. The results showed that with the increasing gum ratio in the mixture, the interfacial tension increased, but the difference was not statistically significant. In emulsions stabilized with gum–protein mixture, increasing gum content, increased the particles size, negative charge on droplets surface, consistency coefficient, yield stress and hysteresis between the forward and the backward diagrams. The particle size distribution curve was monomodal and emulsions stabilized with this mixture showed non–newtonian and psedoplastic behavior. No creaming was observed in all emulsions.  

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Whey protein based edible coating containing 0.5, 1 and 1.5% (w/v) thyme essential oil was used for inhibition of bacterial growth of rainbow trout fillets during cold storage. Microbial analyzes (total viable counts, psychrophilic counts, lactic acid bacteria and Enterobacteriaceaeas) as well as total volatile basic-nitrogen(TVB-N) and pH measuring were performed periodically every four days. Results showed that whey protein coating containing thyme essential oil was able to inhibition of bacterial growth of fish fillets. Also the TVB-N and pH values in the coated samples were significantly (p<0.05) lower than those of non-coated treatment. Among the treatments used in this study, treatment with 1.5% thyme essential oil containing edible coating was the most effective treatment against evaluated bacteria in this study. As could extend the shelf-life of rainbow trout fillets stored at refrigerator for at least 4 days compared to control.  

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Necessity of frozen dough products mostly bread is a daily need of most communities due to its energetic role and being the main meal. The freezing of bread dough, despite of its advantages has some disadvantages like gradual decreasing of dough resistance. The purpose of this research is to investigate the effect of Sodium Stearoyel 2-Lactilat emulsifier (SSL) and whey protein concentrate (WPC) for improving quality of dough and frozen dough structure. Therefore, SSL was used at 0, 0.4, 0.8 % and WPC at 0, 3.75, 7.5 % levels using central composite design. At first, the effect of adding these two substances as independent variables on dough rheological properties was investigated by using farinograph .Then dough samples were stored at -18°C for 1 month and the effect of adding the mentioned substances as independent variables on structure of frozen dough was examined by electron microscoy. Farinograph results showed that adding SSL and WPC had significant effect on water absorption of flour and caused significant increase on the dough development time, dough resistance  and valorimetric value. These results also revealed significant decrease of dough softening degree (P<0.01). The pictures obtained by electron microscopy showed that adding these two substances improved structure of frozen dough. In this research, %0.5 SSL and %3.8 WPC was selected as the best treatment after optimizing results by response surface methology.

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Bread is the major food for a lot of peaple in the world and breadmaking is too long and needs skill. Also, Bread is a food product with short shelf life so for eliminating these problems released frozen bakery products. The freezing of bread dough, despite of its advantages has some disadvantages like decreasing of bread volume, expediting staling and destruction of product finl texture. The purpose of this research is to investigate the effect of Sodium Stearoyel 2-Lactilat emulsifier (SSL) and whey protein concentrate (WPC) for improving quality and staling of the bread from frozen dough. Therefore, SSL was used at 0, 0.4, 0.8 % and WPC at 0, 3.75, 7.5 % levels using central composite design. Dough samples were stored at -18°C for 1 month and the effect of adding the mentioned substances on bagguette bread quality properties was investigated. The results of tuxture profile analysis showed significant effect in the level of 1% about the amount of force applied on bread (P<0.01). Also the results indicated significant effect on increasing spesific volume (P<0.01) and overall admission on sensory evaluation of the bread (P<0.05). In this research, %0.5 SSL and %3.8 WPC was selected as the best treatment after optimizing results by response surface methology.  

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The present research work was aimed to evaluate  the effects of whey protein concentrate (WPC) at different levels of  0, 2, and 4%, as a protein based fat replacer, soy protein isolate (SPI) (0, 1, and 2%) and microbial transglutaminase (MTG) (0, 1, and 2%) on some physical properties of  a low fat  vanilla ice cream (4% fat). Electrophoresis pattern of ice cream proteins and effect of MTG on proteins were analyzed by SDS-PAGE. Total solids of all formulations was adjusted on 34%. Results showed that application of WPC in formulation of low fat ice cream significantly  increased  hardness and melting values, while SPI significantly (P<0.01) increased  hardness and reduced melting value. MTG decreased hardness and melting of ice cream samples compared to the control (P<0.01). Results showed that application of MTG in low fat ice cream was more useful than the utilization of SPI and WPC in terms of hardness and melting properties.

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Abstract
Bioactive peptides are considered specific protein fragments that are inactive within the sequence of the parent protein. After they are released by enzymatic hydrolysis, they may exert various physiological functions. In the present study, response surface methodology was used to optimize hydrolysis conditions for preparing protein hydrolysate from whey protein, using Alcalase 2.4L enzyme. The investigated factors were temperature, time and enzyme/substrate ratio which were selected in the range 43-52°C, 65-175 min and 45-90 AU/Kg protein, respectively to achieve maximum degree of hydrolysis. Experiments were designed according to the central composite design. Each of the studied variables had significant effect on degree of hydrolysis (p<0/05). The optimum conditions to achieve the highest degree of hydrolysis were temperature 49.02°C , time 174.28 min, and enzyme / substrate ratio 90AU/Kg protein. Under these conditions, hydrolysis degree was 41.57 %. Regression coefficient for, chariot models (Quadratic type) was, 0.95. The values indicated the high accuracy of the model to predict the reaction conditions for different variables.