Influence of continuous exposure to gaseous ozone on the quality of red bell peppers, cucumbers and zucchini

The effect of continuous exposure to ozone on quality changes during the storage of red bell peppers, cucumbers and zucchini was investigated. Peppers were stored at 14 °C and were exposed to ozone at 0.1 and 0.3 μmol mol−1, while cucumbers and zucchini were stored at 12 and 8 °C, respectively, and exposed to ozone at 0.1 μmol mol−1. The content of fructose (2.75 g/100 g FW) and glucose (2.00 g/100 g FW) in red bell peppers exposed to ozone at 0.1 μmol mol−1 was increased by 8 and 7%, respectively, when compared to controls. Continuous exposure to ozone at 0.3 μmol mol−1, on the other hand, had no effect on fructose (2.52 g/100 g FW) and glucose (1.88 g/100 g FW) content. The content of vitamin C was significantly enhanced in red bell peppers exposed to ozone at 0.1 and 0.3 μmol mol−1 after 7 d of storage, however, this effect was not maintained. After 14 d, vitamin C content in peppers exposed to ozone at 0.1 μmol mol−1 was not significantly different from the control, whereas it was reduced at 0.3 μmol mol−1. Total phenolics content was increased in peppers exposed to ozone at 0.1 μmol mol−1, but was unaffected at 0.3 μmol mol−1. Continuous exposure of red bell peppers to ozone at 0.1 and 0.3 μmol mol−1 had no significant effect on weight loss, texture and colour. In cucumbers and zucchini, continuous exposure to ozone at 0.1 μmol mol−1 reduced weight loss by more than 40% and improved texture maintenance, while having no significant effect on their biochemistry. The findings from this study suggest that continuous exposure to ozone at 0.1 μmol mol−1 is a promising method for shelf-life extension of cucumbers and zucchini. Even though in red bell peppers continuously exposed to ozone at 0.1 μmol mol−1 sugars and phenolics content was increased, further work is still needed to better understand the exact mechanism of ozone action and its potential for the industrial use

Characterization of kefir-like beverages produced from vegetable juices

The aim of this work was to develop new non-dairy fermented beverages using vegetable juices as fermentable substrates. Carrot, fennel, melon, onion, tomato and strawberry juices underwent backslopping fermentations, carried out by water kefir microorganisms. Results indicated that lactic acid bacteria and yeasts were capable of growing in the juices tested. Melon juice registered the highest numbers of microorganisms. Almost all juices underwent a lactic fermentation. After fermentation, there was observance of a decrease of the soluble solid content and an increase of the number of volatile organic compounds. In particular, esters were present in high amounts after the fermentation, especially in strawberry, onion and melon, whereas carrot and fennel registered a significant increase of terpenes. The concentration of alcohols increased, while that of aldehydes decreased. Changes in colour attributes were registered. Strawberry, onion and tomato juices retained a high antioxidant activity after fermentation. The overall quality assessment indicated that carrot kefir-like beverage (KLB) was the product mostly appreciated by the judges. These findings support the further development of vegetable KLBs with additional benefits and functional properties

Bacterial Stressors in Minimally Processed Food

Stress responses are of particular importance to microorganisms, because their habitats are subjected to continual changes in temperature, osmotic pressure, and nutrients availability. Stressors (and stress factors), may be of chemical, physical, or biological nature. While stress to microorganisms is frequently caused by the surrounding environment, the growth of microbial cells on its own may also result in induction of some kinds of stress such as starvation and acidity. During production of fresh-cut produce, cumulative mild processing steps are employed, to control the growth of microorganisms. Pathogens on plant surfaces are already stressed and stress may be increased during the multiple mild processing steps, potentially leading to very hardy bacteria geared towards enhanced survival. Cross-protection can occur because the overlapping stress responses enable bacteria exposed to one stress to become resistant to another stress. A number of stresses have been shown to induce cross protection, including heat, cold, acid and osmotic stress. Among other factors, adaptation to heat stress appears to provide bacterial cells with more pronounced cross protection against several other stresses. Understanding how pathogens sense and respond to mild stresses is essential in order to design safe and effective minimal processing regimes

Production and quality of kefir cultured butter

Cream is the main raw material for the butter production and reflects its properties into butter quality. Maturation of cream with appropriate starter culture is important for butter quality, sensory properties and shelf life of the end product. Kefir grains contain important probiotics for healthy nutrition including lactic acid bacteria, acetic acid bacteria, and yeasts in high numbers. The aim of this research was to determine the properties of butter produced using natural kefir culture during a 21-day cold storage. Determination of microbial, chemical and sensory properties of butter samples was carried out. Control sample (KOTE) had 6.64 log CFU g-1 Lactococcus spp. while kefir cultured butter samples had 8.58 log CFU g-1. Kefir cultured butter contained 5.24 log CFU g-1 L. acidophilus at Day 1, while control samples did not have L. acidophilus. Acetaldehyde content of kefir cultured butter was significantly higher from the uncultured butter. According to sensory evaluation performed by 12 panelists, KKTE samples had better sensory properties than those observed in the KOTE samples

Effects of rosemary extract and sodium lactate on quality of vacuum-packaged ground ostrich meat

Vacuum-packaged ground ostrich meat patties containing 2% sodium lactate (SL), 0.2% rosemary extract as oleoresin (RE), or their mixture (MIX) were evaluated and compared with control for their storage stability at 3 ± 1°C in the dark by measuring pH, 2-thiobarbituric acid-reactive substance (TBARS) values, sample color (CIE L*, a*, b*, Hue and Chroma), and microbiological content. The pH values of ostrich patties, ranging from 6.03 to 6.13, were not affected by treatment (P < 0.05). At 9 d of storage, TBARS concentration for control samples containing no additives was 1.64 mg malonaldehyde/kg meat. Addition of RE to the ground ostrich meat inhibited lipid oxidation during storage at 3 ± 1°C (P < 0.05). TBARS values of SL-added samples were lower than control samples (P < 0.05); addition of SL also delayed the oxidation. It was found that RE had a protective effect on color, whereas addition of SL decreased CIE a* values (P < 0.05). SL, either alone or with RE, was effective in inhibiting total aerobic bacteria (TAB), coliforms, lactic acid bacteria (LAB), and Brochothrix thermosphacta in ostrich patties (P < 0.05) and provided a 2-log reduction in microbial population during storage. In addition, RE did not have a significant effect on microbial growth at the concentration used in this study