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.

Screening, mutagenesis and protoplast fusion of Aspergillus niger for the enhancement of extracellular glucose oxidase production.

Various strains of Aspergillus niger were screened for extracellular glucose oxidase (GOD) activity. The most effective producer, strain FS-3 (15.9 U mL(-1)), was mutagenized using UV-irradiation or ethyl methane sulfonate. Of the 400 mutants obtained, 32 were found to be resistant to 2-deoxy D: -glucose, and 17 of these exhibited higher GOD activities (from 114.5 to 332.1%) than the original FS-3 strain. Following determination of antifungal resistance of the highest producing mutants, four mutants were selected and used in protoplast fusions in three different intraspecific crosses. All fusants showed higher activities (from 285.5 to 394.2%) than the original strain. Moreover, of the 30 fusants isolated, 19 showed higher GOD activity than their corresponding higher-producing parent strain.

Extension of shelf life of whole and peeled shrimp with organic acid salts and bifidobacteria.

Microbiological and sensory characteristics of treated whole and peeled shrimp from the east coast of Saudi Arabia were evaluated. Shrimp samples were treated with organic acid salts with or without Bifidobacterium breve culture and stored in ice. Peeling alone extended the microbiological shelf life by 4 days. Treatment of whole shrimp with sodium acetate alone or potassium sorbate with bifidobacteria prolonged the microbiological shelf life by 3 days and increased the microbial generation time from 12.8 h (control) to 30.1 h or 31.4 h, respectively. The microbiological and sensory shelf life of peeled shrimp treated with sodium acetate was more than 17 days. Sodium acetate extended the microbial lag phase and lengthened the generation time (38.7 h compared to 15.8 h for the control). Micrococci and coryneforms were the predominant microorganisms in whole shrimp during storage. Treatment with sodium acetate maintained better sensory characteristics for peeled shrimp than potassium sorbate combined with bifidobacteria.