The present study aimed at investigating the effects of octenylsuccinylation and particle size on the emulsifying properties of starch granules as Pickering emulsifiers. Starch spherulites (1-5 μm), native rice starch (5-10 μm), waxy maize starch (10-20 μm) and waxy potato starch (20-30 μm) were modified with octenylsuccinic anhydride. Results showed that octenylsuccinylation caused a significant increase in the contact angle, and there was a weak positive linear correlation with the emulsifying capacity of the starch granules. After octenylsuccinylation, smaller particles of octenylsuccinate-starch granules exhibited better emulsifying properties with smaller droplet size and lower creaming index. Overall, both octenylsuccinylation and particle size have important effects on the emulsifying properties of starch granules as Pickering stabilizers. This study could be useful in the design and development of starch-based Pickering emulsifiers, and provide potential applications in the food and pharmaceutical industries.
l-Asparaginases have the potential to inhibit the formation of acrylamide, a harmful toxin formed during high temperature processing of food. A novel bacterium which produces l-asparaginase was screened. Type I l-asparaginase gene from Acinetobacter soli was cloned and expressed in Escherichia coli. The recombinant l-asparaginase had an activity of 42.0 IU mL-1 and showed no activity toward l-glutamine and d-asparagine. The recombinant l-asparaginase exhibited maximum catalytic activity at pH 8.0 and 40°C. The enzyme was stable in the pH ranging from 6.0 to 9.0. The activity of the recombinant enzyme was substantially enhanced by Ba2+, dithiothreitol, and β-mercaptoethanol. The Km and Vmax values of the l-asparaginase for the l-asparagine were 3.22 mmol L-1 and 1.55 IU μg-1, respectively. Moreover, the recombinant l-asparaginase had the ability to mitigate acrylamide formation in potato chips. Compared with the untreated group, the content of acrylamide in samples treated with the enzyme was effectively decreased by 55.9%. These results indicate that the novel type I l-asparaginase has the potential for application in the food processing industry.
Murraya koenigii leaf extract antioxidant potentials were evaluated in palm olein using accelerated oxidation storage and deep-frying studies at 180 degrees C for up to 40 h. The extracts (0.2%) retarded oil oxidation and deterioration significantly (P<0.05), slightly less effectively than 0.02% butylated hydroxytoluene in tests such as the peroxide value, anisidine value, iodine value, free fatty acid, Oxidative Stability Index, and polar and polymer compound content. Sensory evaluation on French fries indicated that the extract was useful in improving colour, flavour and overall acceptability and the quality of the fried product. All samples were more acceptable by panellists, especially after the 40th hour frying, compared with those similarly fried in the control oils and the oil containing butylated hydroxytoluene. M. koenigii leaf extract, had a polyphenol content of 109.5+/-0.3 mg gallic acid equivalents/g extract, and contain a heat-stable antioxidant that could be a natural alternative to synthetic antioxidants for the industry.