Evaluation of In Vitro Antioxidant, Anti-Obesity, and Anti-Diabetic Activities of Opuntia ficus Cladodes Gel and Its Application as a Preservative Coating for Shrimp during Refrigerated Storage.

Opuntia ficus cladodes (OFC) are considered one of the wastes that result from opuntia cultivation, and their disposal by traditional methods results in many environmental problems. Therefore, this study was conducted with two aims. The first was the production of OFC gel, and the evaluation of its in vitro antioxidant (by two methods, DPPH and ABTS), anti-obesity, and anti-diabetic activities. The second was an investigation of the effects of different concentrations of this gel (0, 50, and 100%) as an edible coating on the quality of shrimp during 8 days of refrigerated storage. The results showed that this gel was characterised by a high content of ash (10.42%), total carbohydrates (75.17%), and total phenols (19.79 mg GAE/g). OFC gel contained six types of sugars: arabinose, xylose, galactose, rhamnose, glucose, and uronic acid, and the most abundant was xylose (36.72%). It is also clear from the results that the OFC gel had high antioxidant properties, which were higher against DPPH than ABTS at the same concentration. OFC gel showed a high inhibition activity against lipase, α-glycosidase, and α-amylase enzymes, and their IC50 values were 1.43 mg/mL, 0.78 mg/mL, and 0.57 mg/mL, respectively. The results also stated that shrimp coated with OFC gel had lower pH, drip loss, TVB-N, and TBA values through the days of refrigerated storage. Moreover, the shrimp coated with 100% OFC gel were better than those coated with 50% OFC gel. In conclusion, OFC gel showed high potency as active antioxidant, for its enzyme anti-activities, and as an edible coating for shrimp.

Impact of fermentation conditions on the physicochemical properties, fatty acid and cholesterol contents in salted-fermented hoki roe.

Hoki (Macruronus novaezelandiae) roes were used to produce a salted fermented (jeotgal-like) roe product at 4 °C and 25 °C. The impact of the fermentation temperature on the microbiological status, proximate analysis, acidity, colour, fatty acid profile and cholesterol content were determined over a 4-week fermentation period. Total bacterial count and total LAB (expressed as log CFU) increased with fermentation time (p < 0.001). Fermentation temperature did not affect the proximate analysis, but fermentation time increased both the ash content and decreased the protein and moisture contents in the roe (p < 0.001, for all). Products produced at 25 °C had a lighter colour (p < 0.001) compared to products produced at 4 °C. Fermentation did not affect the roe fatty acid profile, but cholesterol content in the roe was reduced (p < 0.001) at both fermentation temperatures. Results suggest that fermentation can be a feasible approach to reduce cholesterol levels in fish roe.