Tomato peroxidase (POD) was inactivated by heat and ultrasound. Thermal inactivation of tomato POD was performed at temperatures of 63, 64, 65, 66 and 67°C. Thermal inactivation of POD in tomato showed apparent first-order kinetics. E(a) was calculated from the slopes of Arrhenius plot and found as 14.9×10(4) J/mol. The effect of ultrasound on tomato peroxidase inactivation was investigated at 15%, 25%, 40%, 50% and 75% ultrasonic powers for 20-150 s. It was observed that as the ultrasonic power increased, inactivation rate increased. 100% POD inactivation was observed at 50% power for 150 s and at 75% power for 90 s of ultrasonication. Regeneration of POD activity was investigated for the samples exposed to ultrasound at different ultrasonic powers. It was observed that at 15% and 25% ultrasonic powers, residual enzyme activity increased linearly, whereas at powers of 40%, 50% and 75% residual enzyme activity increased nonlinearly. There was no regeneration in the samples which 100% enzyme inactivation obtained by ultrasound. A significant decrease in vitamin C content of tomato extract was observed as a function of temperature and treatment time, whereas ultrasonic treatment had no significant effect on vitamin C content of tomato extract.

Ultrasound is versatile and innovative technology due to its wide range of application and increase in knowledge and research studies. It is used in food industry for many purposes including analysis methods and food processings such as freezing, cutting, drying, tempering, homogenization, degassing, antifoaming, filtration and extraction. Ultrasound can be used as a promoter or alternative to food processing. There may be numereous advantages of using ultrasound for food processing such as effective mixing, increased mass transfer, reduced energy, reduced temperature and increased production rate. Due to the elimination of microorganisms and enzymes without destroying nutrients of foods, ultrasound can be used as an alternative method to thermal treatments in the food preservation. Additionally, low power ultrasound is thought to be an attractive nonthermal method due to overcome problems which occur during heat treatments such as physical and chemical changes, nutritional loss and change in organoleptic properties. This review summarizes mechanism, operation and latest potential applications of ultrasound in the food preservation.

The term "biogenic amines" defines decarboxylation products such as histamine, putrescine, serotonin, tyramine, phenylethylamine, tryptamine and also aliphatic polyamines. They can be detected in both raw and processed foods. In the recent years, there is a great interest in biogenic amines as they are associated with quality, safety and freshness of some foods, particularly fermented foods. The presence of biogenic amines in foods can also be used as an indicator of hygienic quality. Biogenic amines also cause health hazards due to their toxic effects especially in sensitive individuals. It is therefore important to control and reduce the biogenic amines. The reduction can be brought about by the use of high pressure, irradiation, packaging, additives, starter cultures and by reduction of decarboxylase activity and temperature. This review summarizes the significance, function, occurrence and formation of biogenic amines in different foods and their reduction by different methods.

Kashar is one of the most consumed traditional cheeses in Turkey. It is produced as fresh or mature, which differ in ripening periods. Safe consumption period of kashar was investigated during refrigerated storage. Five samples of fresh and five samples of mature kashar cheeses collected from local supermarkets in Turkey were analyzed. Changes in biogenic amines, pH and thiobarbituric acid reactive substance of fresh and mature kashar cheeses were investigated during storage. Mature kashar cheeses had higher biogenic amine concentrations than fresh kashar cheeses. During storage, total biogenic amine contents of all samples increased significantly (p<0.05). Total biogenic amine contents of mature kashar cheeses were higher than maximum allowed limit of 1000 mg/kg and can cause toxicity. It was found that fresh kashar cheeses were safer than mature kashar cheeses with respect to the toxic limits of biogenic amines.

This study aimed to assess the survival of probiotic cultures in kefir. Kefir is a fermented dairy product, and in this study we incorporated nutritionally rich flaxseed mucilage and gum arabic as a prebiotic, then monitored for improvement in the the viability of Lactobacillus acidophilus and Bifidobacterium lactis. In addition, some physicochemical variables of kefir were investigated. The addition of flaxseed mucilage and gum arabic significantly (p ˂ 0.05) increased the growth of both Lactobacillus acidophilus and Bifidobacterium lactis compared to the control. Samples enriched with flaxseed mucilage and gum arabic had significantly (p ˂ 0.05) reduced pH and increased viscosity. Flaxseed mucilage and gum arabic significantly (p ˂ 0.05) changed the color parameters L*, a*, and b*. However, as the concentration of flaxseed mucilage increased, the L* value decreased. Moreover, adding flaxseed mucilage and gum arabic into kefir increased (p ˂ 0.05) the protein content. These results showed that flaxseed mucilage and gum arabic could be used to increase the survival of probiotic cultures in kefir without changing its physicochemical properties.