Fatemeh Karegar; Rezvan Pourahmad; Peyman Rajaei
Abstract
[1]Introduction: Nowadays, with the development of probiotic products on the world market, the need for developing new products containing probiotic bacteria becomes more apparent. Probiotics are defined as living microorganisms that, if consumed in sufficient quantities, will have beneficial effects ...
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[1]Introduction: Nowadays, with the development of probiotic products on the world market, the need for developing new products containing probiotic bacteria becomes more apparent. Probiotics are defined as living microorganisms that, if consumed in sufficient quantities, will have beneficial effects on the health of the host. Probiotics are now widely used in the production of food products and account for approximately 65% of functional foods. Probiotics often belong to either the genus Lactobacillus or Bifidobacterium. Lactobacillus rhamnosus is one of the known probiotic bacteria with beneficial properties. Prebiotics are defined as indigestible compounds, mainly carbohydrates that can be used as carbon source for probiotic bacteria and stimulate their growth and viability. Oligofructose is a type of short chain inulin and is one of the most well- known prebiotics. Moreover, microencapsulation of probiotic bacteria can improve the survival of these bacteria. In this approach, living probiotic cells are covered or trapped by various compounds. Hydrocolloids such as alginate and carbohydrates such as starch can be suitable compounds for microencapsulation. The purpose of this study was to investigate the effect of oligofructose and microencapsulation on the viability of Lactobacillus rhamnosus, textural, physicochemical and sensory characteristics of functional jelly. Materials and methods: In this study, different concentrations (0, 1.5 and 3 percent) of oligofructose as prebiotic were used to produce jelly samples, and 107 CFU/mL of probiotic bacteria (free and microencapsulated Lactobacillus rhamnosus) was inoculated. Microencapsulation of probiotic bacteria was performed by emulsion method using sodium alginate and corn resistant starch. The jelly samples were stored at 4˚C for two weeks. pH, acidity, dry matter, firmness, probiotic bacterial count and sensory properties (taste, odor, texture, color and overall acceptance) of the samples were evaluated on the first, 7th and 14th days of jelly production. Seven samples including 6 treatments and 1 control sample (without probiotic bacteria and prebiotic compound) with three replications were studied. The data were subjected to analysis of variance (ANOVA), followed by the Duncan’s multiple range test to determine the significant difference between samples at 95% confidence level (p<0.05) using the SAS 9.4 M4 Software. The charts were drawn by Excel 2013. Results and discussion: The results of sensory evaluation showed that the effect of different percentages of oligofructose on the sensory parameters, except for the taste, was not significant (p>0.05). Using 1.5% oligofructose and probiotic bacteria (free or microencapsulated) did not change the score of taste but the use of 3% oligofructose and free probiotic bacteria decreased the score of this parameter. The effect of storage time on sensory properties (taste, odor, texture, color and overall acceptance) was significant (p<0.05) so that with increasing storage time, the score of sensory parameters decreased. The results of physicochemical tests indicated that with increasing oligofructose, dry matter increased and acidity decreased (p<0.05). The results of texture analysis showed that the microencapsulation of probiotic bacteria and addition of oligofructose significantly (p<0.05) increased the firmness of jelly texture. During storage period, pH and dry matter significantly (p<0.05) decreased but acidity and firmness of jelly texture increased. The results of probiotic bacterial count indicated that the use of microencapsulated probiotic bacteria and oligofructose significantly (p<0.05) increased the survival of Lactobacillus rhamnosus. The viability of probiotic bacterai decreased during storage period, t however, the number of probiotic bacteria in the samples was in the range of 106- 107 CFU/g. On the first and 7th days, no mold and yeast contamination was observed in the samples and on the 14th day, the number of molds and yeasts was less than 10 CFU/g. The sample containing microencapsulated probiotic bacteria and 3% oligofructose (sample 4) was selected as the best sample in terms of probiotic bacterial count and textural, physicochemical and sensory quality. Therefore, it is possible to produce synbiotic jelly with the desired quality
Nafiseh Karimi; Rezvan Pourahmad; Salman Taheri; Orang Eyvazzadeh
Abstract
Introduction: Yogurt contains valuable compounds, some of which enter yogurt whey and if discarded, remains unused. Yogurt whey has a high nutritional value due to its high quality biological proteins which can be a good source of bioactive peptides. Bioactive peptides are food-derived peptides that ...
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Introduction: Yogurt contains valuable compounds, some of which enter yogurt whey and if discarded, remains unused. Yogurt whey has a high nutritional value due to its high quality biological proteins which can be a good source of bioactive peptides. Bioactive peptides are food-derived peptides that are small in size and usually consist of 3- 20 amino acids. These peptides are considered as functional ingredients. Bioactive
peptides have antioxidants and antimicrobial properties. The aim of this study was to investigate the effect of adding bioactive peptide derived from enzymatic hydrolysis of yogurt whey on physicochemical, sensory and microbial properties of doogh during storage.
Materials and Methods: In this study, peptide derived from tryptic hydrolysis of yogurt whey protein fractionated by RP- HPLC was used. Minimum inhibitory concentration (MIC) and Minimum bactericidal concentration (MBC) of this peptide were determined against Staphylococcus aureus and Escherichia coli. This peptide was incorporated to heated doogh at concentrations of 12, 20, 24, 40, 48, and 80 mg/mL. Moreover, doogh samples were inoculated with 106 CFU/mL Staphylococcus aureus and Escherichia coli. Doogh samples were stored for two months. During 60 days storage, bacterial count, pH, acidity, ABTS radical cation inhibitory activity and sensory properties (taste, odor, texture, color and overall acceptance) of doogh samples were studied.
Results and Discussion: The MIC of yogurt whey peptide against Staphylococcus aureus and Escherichia coli was 12.2 and 24.4 mg/mL, respectively. Moreover, the MBC of yogurt whey peptide against Staphylococcus aureus and Escherichia coli was 12.2 and 48.8 mg/mL, respectively. Addition of this peptide to doogh showed that during storage period, the Staphylococcus aureus and Escherichia coli counts, pH and ABTS cation radical inhibitory activity of the samples were significantly decreased, but acidity was increased (p<0.05). The peptide of yogurt whey showed good antioxidant and antibacterial activities in doogh samples. By increasing the level of peptide in samples, the ABTS cation radical inhibitory activity was significantly increased (p<0.05). During storage, the control sample (without bioactive peptide) showed the highest reduction in antioxidant activity and the lowest reduction was related to the sample containing 48.8 mg/mL bioactive peptide. The ABTS cation radical inhibitory activity of the control sample and sample containing 48.8 mg/mL bioactive peptide was 9.72 and 3.66 Unit/mL, respectively on the 60th day. By increasing the levels of bioactive peptide, pathogenic bacteria counts were decreased (p<0.05). The sample containing the highest level of peptide (48.8 mg/mL) was free of Staphylococcus aureus and E. coli on the 20th day of storage. The control sample and samples containing 12.2 and 24.4 mg/mL bioactive peptide were free of these pathogenic bacteria on the 60th and 40th days, respectively. The highest rate of acidity and pH changes was related to the control sample and sample containing 48.8 mg/mL bioactive peptide had the lowest changes during storage. The acidity of control sample and sample containing 48.8 mg/mL bioactive peptide was 0.68 and 0.56% lactic acid, respectively on the 60th day.The results of sensory evaluation showed that in the control sample and sample containing the lowest level of peptide (12.2 mg/mL), the score of sensory characteristics decreased during the storage period, however, the use of the highest level of yogurt whey peptide (48.8 mg/mL) in the doogh formulation was able to reduce the rate of loss of sensory properties and maintain product quality over time. The sample containing 48.8 mg/mL bioactive peptide had the highest score of overall acceptability. Finally, the concentration of 48.8 ppm peptide can be considered as the best level to enrich the doogh in terms of physicochemical, microbial and sensory properties. Therefore, it is concluded that bioactive peptide derived from yogurt whey can be used as a natural antioxidant and antimicrobial agent in fermented dairy products like doogh.
Maryam Ein Ali Afjeh; Rezvan Pourahmad; Behrouz Akbari Adergani; Mehrdad Azin
Abstract
Introduction: The aim of this study was to investigate the effect of immobilized glucose oxidase on magnetic chitosan nanoparticles on the content of organic acids (lactic acid and acetic acid), viability of probiotic bacteria and sensory properties of probiotic drinking yogurt.
Materials and ...
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Introduction: The aim of this study was to investigate the effect of immobilized glucose oxidase on magnetic chitosan nanoparticles on the content of organic acids (lactic acid and acetic acid), viability of probiotic bacteria and sensory properties of probiotic drinking yogurt.
Materials and methods: Different concentrations (0, 250, 500, 750 and 1000 mg/kg) of free and immobilized glucose oxidase were used in probiotic drinking yogurt. The samples were stored at 4˚C for three weeks.
Results and discussion: During storage, the content of acetic acid, counts of Lactobacillus acidophilus and Bifidobacterium lactis decreased and the content of lactic acid increased significantly (p<0.05). Addition of enzyme increased the viability of probiotic bacteria in test samples as compared to control sample (without enzyme). The viability of Bifidobacterium lactis in the samples containing high levels of enzyme (750 and 1000 mg/kg) was higher than other levels. The samples containing 500 mg/kg of free and immobilized enzyme had the highest count of Bifidobacterium lactis (7.88 log CFU/mL) and the amount of acetic acid in these samples (0.82 and 0.87 g/L, respectively) was more than other samples. There was no significant difference between the samples in regards to sensory properties. Therefore, addition of glucose oxidase immobilized on magnetic chitosan nanoparticles can decrease oxidative pressure and create suitable condition for the viability of probiotic bacteria in drinking yogurt and maintain overall acceptability. Moreover, it is economically feasible.
