Food Technology
Aliakbar Gholamhosseinpour; Ali Karimi Davijani; Mostafa Karami
Abstract
Introduction: Cheese is the general name of a group of fermented dairy products that are produced all over the world in a variety of flavours, textures, and shapes. This product contains various proteins, minerals, and vitamins, all of which add to its high nutritional quality. White-brined cheeses are ...
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Introduction: Cheese is the general name of a group of fermented dairy products that are produced all over the world in a variety of flavours, textures, and shapes. This product contains various proteins, minerals, and vitamins, all of which add to its high nutritional quality. White-brined cheeses are soft cheeses that ripen in brine. Today, brined ultrafiltered cheese, as a popular product, has allocated a broad consumer market in our country. The use of thermal processes to prolong the shelf life of foods has long been considered, but these methods lead to a decrease in nutritional value and product quality. Emerging non-thermal technologies, including ultrasound, pulsed electric field, high hydrostatic pressure, cold plasma and ozone have revolutionized the food processing sector. These processes can improve the safety and quality of food products and increase their shelf life by reducing food spoilage. In addition to increasing food storage time, these technologies are expanding in the industry due to reduced energy consumption. Ozone is one of the most effective disinfectants known that does not leave any dangerous residue on food or other surfaces in contact with it. Ozone treatment does not require heat and therefore saves energy. Ozonation, as a novel technology, is widely used in preserving meat, processing oysters, inhibiting microbial growth, and oxidizing phenolic compounds. Ozone has been mainly used in the dairy industry to reduce or inhibit the growth of pathogenic or spoilage microorganisms, in contrast, its effect on the non-microbial properties of dairy products has not been studied much.Materials and methods: Cheese production was carried out by ultrafiltration technology in the Hamedan Pegah dairy complex (Hamedan, Iran). The starter culture used in cheese production was R708 (containing Lactococcus lactis subsp. Cremoris and Lactococcus lactis subsp. Lactis), which was obtained from Christian Hansen, Denmark. Microbial renin enzyme (Proteria, Handry company, Belgium) was also used for coagulation. Analytical grade chemicals were also purchased from Merck, Darmstadt, Germany. Ozone gas at concentrations of 2 and 5 ppm was used in different stages of brined ultrafiltered cheese production and then the samples were subjected to physicochemical (total solids (TS), ash, pH, salt, protein, fat, acid degree value (ADV)), microbiological and organoleptic (based on the 5-point hedonic scale) analyses at 35-day intervals during a ripening period of 105 days. Ozone treatments were: Ozonization of concentrate simultaneously with starter inoculation (OA), Ozonization of concentrate before starter inoculation (OB), Ozonization of concentrate (before starter inoculation) and brine (OC), Ozonization of brine (OD) and control (C). Statistical analysis (One-way ANOVA and Duncan) was performed at a significance level of 95% by the SPSS package program (v. 20.0, Chicago, IL, USA).Results and discussion: Based on the results, the amounts of total solids, ash, salt, ADV and syneresis of cheeses increased significantly (p ≤ 0.05), while the protein and fat contents of the samples decreased significantly (p ≤ 0.05) during the ripening period. The pH of the samples decreased from day 0 to 35 and then increased in most samples until the end of the ripening period. The total counts in the samples increased initially until day 70 but then decreased until the end of the ripening period. In general, during the ripening, cheeses treated with 5 ppm ozone had lower microbial load and higher lipolysis compared to samples treated with 2 ppm ozone. In addition, in most treatments, the sensory scores of cheeses at the end of the ripening period were significantly (p ≤ 0.05) higher than those at the beginning of the ripening period. Although the use of ozone treatment was able to improve some of the sensory properties of the cheeses, in general, this increase was not significant compared to the control, especially at the end of the ripening period.The positive microbial and physicochemical effects of ozone treatment on cheese samples increased the shelf life of brine cheese up to 105 days (30 days more than usual) without having a negative effect on its sensory properties. Therefore, ozone can be used as a non-thermal treatment to increase shelf life and improve some physicochemical characteristics of cheese.
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.
Hamed Hosseini; Mohammad Ghorbani; Alireza Sadeghi Mahoonak; Yahya Maghsoudlou
Abstract
Oxidative stability of walnut (Juglansregia L.) was evaluated over a period of 1 year storage in various conditions. The whole walnuts, walnut kernels, walnut chopped kernels, walnut kernels packaged in polyethylene (PET) under vacuum and poly propylene (PP) contain of CO2 were kept in a normal condition ...
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Oxidative stability of walnut (Juglansregia L.) was evaluated over a period of 1 year storage in various conditions. The whole walnuts, walnut kernels, walnut chopped kernels, walnut kernels packaged in polyethylene (PET) under vacuum and poly propylene (PP) contain of CO2 were kept in a normal condition (temperature, 19-30˚С and relative humidity (RH), 35-45%). The whole walnuts and walnut kernels were also kept in refrigerator (4˚С, RH 75%). Some quality parameters for the oil extracted from walnut kernels were measured throughout the storage. Peroxide value of whole walnuts, walnut kernels and walnut chopped kernels pass over 2 meq O2/kg after 12, 10 and 8 months storage, respectively. Peroxide value of the packaged nuts and the nuts stored at cold storage were increased only 1 meq O2/kg over a period of 1 year storage. According to the statistically analysis results, the effect of storage condition and storage time on oxidative stability of walnuts were significant (p walnuts shell > contact surface of walnut kernels with environment were defined to maintain the quality of walnut kernels during long term storage.
