جستجوی مقالات مرتبط با کلیدواژه "red grape juice" در نشریات گروه "صنایع غذایی"

Cold plasma is a non-thermal technology and a suitable alternative to conventional thermal methods used in the food industry, which, with its antimicrobial properties, increases the shelf life of food products without negatively affecting their quality. The purpose of this research is to investigate the physicochemical, microbial and sensory properties of red grape juice pasteurized by cold plasma method (under plasma irradiation with voltage of 20, 40 and 60 kV for a period of 1, 2, 3 and 4 min and air gas) and compare it with thermal pasteurization (95°C for 5 seconds). The results showed that the effect of treatment on physicochemical properties (acidity, pH and Brix), bioactive compounds (anthocyanin, total phenol and vitamin C), color properties (components a*, b* and L*), microbial load (mold and yeast, aerobic bacteria and coliform) and sensory characteristics (taste, smell and overall acceptance) of red grape juice pasteurized by cold plasma method was significant (p≤0.05) so that with increasing amount voltage from 20 to 60 kv and time from 1 to 4 min, in grape juice pasteurized by cold plasma method, the amount of acidity, brix, color components a* and b* increased significantly (p≤0.05) and the amount pH, bioactive compounds (anthocyanin, total phenol and vitamin C), the amount of color of L* component, the amount of microbial load (mold and yeast, aerobic bacteria and coliform) decreased significantly (p≤0.05). Also, by increasing the time from 1 to 4 min, the smell score and overall acceptance decreased, and by increasing the voltage from 20 to 60 kV and the time from 1 to 4 min, the taste score decreased. Since the physicochemical, color, microbial and sensory changes of red grape juice pasteurized by cold plasma method in the conditions of 40 kv, 4 min time and air gas were less than thermal pasteurization method and more acceptable for consumption, it was introduced as a superior treatment.

Thermal pasteurization destroys bioactive compounds. Therefore, there is a need for a technique that provides microbial stability and stability while preserving biologically active compounds in grape juice. In recent years, the application of ultra-sonication in food processing has been considered for its ability to deactivate microorganisms with very little or no effect on bioactive compounds and nutritional properties of food. Ultrasound is considered as one of the potential non-thermal pasteurization techniques in the production of juices and is an effective method for maintaining the qualitative properties of juices. These properties have the advantage of thermal pasteurization. The purpose of this study was to investigate the effect of thermal ultrasound in comparison with the usual pasteurization method on bioactive compounds and some characteristics of red grape juice (Brix, pH, acidity, vitamin C, phenolic content, antioxidant properties and anthocyanin content).

In this research, the red grape juice was prepared from the fruit. The treatments were: controlled sample (without treatment), pasteurized sample (90 °C,30˝), heated sample at 60 °C for 4,8,12 min, ultrasound sample without heating for 4,8,12 min with amplitudes of 24.4, 42.7, 61 μm, ultrasound sample with heating (60 °C) for 4,8,12 min with 24.4, 42.7 and 61 μm amplitudes. The effect of treatments on Brix, pH and acidity, phenilic content, ascorbic acid content, antioxidant activity and anthocyanin content of the samples were investigated.

According to the results, the treatments did not have a significant effect on the pH, pH, and acidity of red grape juice. Pasteurization treatment caused the greatest reduction in the qualitative characteristics of the samples. The highest percentage of degradation of ascorbic acid content in red grape juice was 28.2% which was related to pasteurization treatment, and high temperatures at 60 ° C and long duration also had the most significant decrease in ascorbic acid compared to other treatments. The highest phenolic content was observed in treatment with temperature of 25 ° C and duration of 4 minutes with intensity 61 μm. The antioxidant activity of juice was significantly reduced by pasteurization and high temperatures with high levels. The highest antioxidant activity was related to treatment at 25 ° C for 8 minutes and 61 μm intensity, which increased antioxidant activity compared to control sample of 16.4%. Pasteurization treatment reduced 7.4% of the anthocyanin content of red grape juice and at high levels of sonication, increasing the duration and treatment temperature had a negative effect on the content of anthocyanin and reduced it to 7.9%.

According to the results of this study, it can be stated that pasteurization treatment in most cases had a negative effect on the qualitative traits of red grape juice and by using thermosonication in producing red juice at lower temperatures than pasteurization, higher qualitative traits can be achieved. Therefore, the use of average values of ultrasound intensity (42.7 μm) at 60 ° C for red grape juice is recommended.

Production of probiotic non-dairy food has a great attention. The objective of this study was to investigate the survival of Lactobacillus acidophilus type LA-5 and L. casei type 431 in red grape juice during storage at refrigerated condition for 4 weeks. Red grape juice with Brix 15 prepared and pasteurized at 80 ºC for 4 min. A preliminary fermentation of juice containing both bacteria was done at 37 ºC for 3 days was done and all treatments were maintained at 4 ºC for 4 weeks. Survival of bacteria, Brix, titrable acidity, pH, and total sugar contents were measured during fermentation and storage period. The results showed that after 4 weeks of storage at 4 ºC, the viable cell counts of L. acidophilus were stabilized at 2.1×108 cfu/mL, while L. casei did not survive the low pH and high acidity conditions in red grape juice and declined to its lowest level as 5 ×104 cfu/mL. The results also showed that L. acidophilus made increase in acidity during the stages of fermentation (P≥ 0.05) and the storage time and the sugar consumption and reducing of Brix was also higher in L. acidophilus compared with L. casei. It is concluded that red grape juice could serve as a raw material for the production of probiotic juice by L. acidophilus as compared by incorporating L. casei.