Effect of UV–Vis irradiation on enzymatic activities and the physicochemical properties of nectarine juices from different varieties

Effect of ultra violet (UV-C) and cold storage on orange juice quality

The effect of the UV-C treatment on the physico-chemical characteristics, pectin methylesterase activity (PME) as well as microbial quality of orange juice, compared to fresh juice, was studied. The juice samples were UV-C (254 nm) irradiated for different exposure times (15, 30, 45 and 60 min) and stored at 4 ± 1 °C for 30 days. UV-C treatment didn't significantly (p ≤ 0.05) affect pH values, titratable acidity, TSS (%), ascorbic acid content and PME activity in both fresh and stored samples. Increasing the exposure time from 5 to 60 min. showed no significant effect (p ≤ 0.05) on L* and a* values for both the fresh and the stored samples. On the contrary, negative relationship was observed between UV-C exposure time and b* values. Total bacterial counts were significantly (p ≤ 0.05) reduced from 2.69 to 0.93 log10 CFU/mL when the exposure time was increased from 0 to 60 min. The UV-C treatment showed similar trend on yeast and mold counts but to a lesser extend due to their resistance to UV. The sensory characteristics, i.e. odour, colour, taste, consistency and overall acceptability didn't change (p ≤ 0.05) as a result of UV-C treatment at any tested exposure times.

Removal of organic matter from wastewater coming from fruit juice production using solar photo-Fenton process

The grape juice production generates an industrial wastewater that has a high concentration of organic matter and several polyphenols, such as ethanol. Therefore, the discharge of this wastewater can produce environmental problems. The aim of this work was to determine the optimal concentration of the reagents involved in a solar photo-Fenton process in the treatment of wastewater coming from juice. The process was analysed in a factorial design, as a function of H2O2 (900, 1000, 1100 mg/L) and Fe2+ (90, 100, 110 mg/L) concentration. The grape juice wastewater presents high organic content (20,500 mg/L COD and 5.4 mg/L polyphenols). Also, the presence of alcohols such ethanol, ethyl acetate and 2-metil-1-propanol was confirmed. The results showed that highest COD (>27%) and polyphenols removal (>36%) were obtained in experiments with 1100 mg H2O2/L and 100 mg Fe2+/L. In treatments with higher COD removal, 2-metil-1-propanol was detected as an intermediate of ethanol oxidation. These results proved that solar photo-Fenton is a suitable approach for treating the refractory organic matter from grape juice.

Effect of pulsed light treatment on enzymes and protein allergens associated with their structural changes: a review

The pulsed light (PL) technique is used for food and surface decontamination widely. The sterilization effect of PL is well known and identified as the photo-chemical effect. Besides, PL is used to inactivate enzymes, reduce the immunoreactivity of proteins, and change protein function properties at a laboratory level. The current study aims to review the effect of PL on proteins by highlighting the differences between proteins in buffer solutions or food systems. Although PL is known as a non-thermal technique, most studies done on food systems, food temperature raised considerably. Therefore, PL inactivated many enzymes in buffer solution non-thermally, while mostly with a high increase in temperature of a food system. PL reduced food allergens several folds in some foods. However, immunoreactivity responses of some protein were increased after PL treatment. Also, the current study covers the conformational changes of proteins that occur because of PL treatment. Therefore, some techniques used to follow proteins structural changes such as polyacrylamide gel electrophoresis (SDS-PAGE), high-performance liquid chromatography (HPLC), Fourier-transform infrared spectroscopy (FTIR), etc. were defined. Studies reported that PL altered proteins structure differently. For example, some studies reported that PL degraded some proteins, while other studies suggested that PL aggregated proteins. Also, there were contrary results regarding α-helix and ß-sheet concentration for the treated proteins. In conclusion, some techniques, such as amino acid sequencing, specially when some small new fragments proteins appeared on SDS-PAGE, should be used to detect the effect of PL on proteins precisely.

Comparative Effects of Thermal, High Hydrostatic Pressure, and UV-C Processing on the Quality, Nutritional Attributes, and Inactivation of Escherichia coli, Salmonella, and Listeria Introduced into Tiger Nut Milk

HIGHLIGHTS

Thermal and nonthermal methods can support a 5-log CFU reduction of model bacteria introduced into tiger nut milk. Thermal treatment of tiger nut milk results in significant loss of protein, antioxidants, and quality properties. HHP or UV-C treatment of tiger nut milk retains quality and nutritional characteristics. HHP or UV-C are suitable for the pasteurization of tiger nut milk.