Mechanisms of folate losses during processing: diffusion vs. heat degradation.

Though folates are sensitive to heat treatments, leaching appears to be a major mechanism involved in folate losses in vegetables during processing. The aim of our study was to study folate diffusivity and degradation from spinach and green beans, in order to determine the proportion of each mechanism involved in folate losses. Folate diffusivity constant, calculated according to Fick's second law (Crank, 1975), was 7.4×10(-12) m(2)/s for spinach and 5.8×10(-10) m(2)/s for green beans, which is the same order of magnitude as for sugars and acids for each vegetable considered. Folate thermal degradation kinetics was not monotonous in spinach and green beans especially at 45 °C and did not follow a first order reaction. The proportion of vitamers changed markedly after thermal treatment, with a better retention of formyl derivatives. For spinach, folate losses were mainly due to diffusion while for green beans thermal degradation seemed to be preponderant.

Clean recovery of antioxidant flavonoids from onions: optimising solvent free microwave extraction method.

A solvent free microwave hydrodiffusion and gravity extraction (MHG) of flavonol content from onion (Allium cepa L.) was studied. Effectiveness of this innovative method in extraction of onion total phenolic content, total quercetin (TQ), quercetin aglycon (QA), quercetin-3,4'-diglucoside (QDG), quercetin-4'-monoglucoside (Q4G), quercetin-3-monoglucoside (Q3G), kaempferol (KMF) and myricetin (MRT) have been evaluated and compared with conventional solvent extraction. Microwave extraction offers important advantages like shorter extraction time (23min), cleaner feature (no solvent or water used) and extraction of valuable onion crude juice retaining fresh organoleptic properties with higher phenolic content (58.29mgGAE/gDW) at optimized power (500W). Microwave extraction resulted significant yield (81.5%) with 41.9% of flavonol contents, with better retain of remaining flavonoids (55.9%) in residues of onions. QDG (239.7mg/100gDW) and Q4G (82.55mg/100gDW) have been reported the main flavonol in this study. Minor quantities of QA (traces), Q3G (4.22mg/100gDW) and KMF (3.99mg/100gDW) were also detected in microwave onion extracts.

Injury and Lethality of Heat Treatment of Bacillus cereus Spores Suspended in Buffer and in Poultry Meat.

The effect was studied of supplementing the recovery medium with lysozyme, glucose, NaCl, and MgSO4 on the apparent heat resistance of four strains of Bacillus cereus . The composition of an optimal medium (allowing the germination and growth of all surviving spores) and of a selective medium (inhibiting injured spores) was then determined: the optimal medium consisted of nutrient agar supplemented with 50 × 10-6 g of lysozyme and 0.5 g of MgSO4 per liter. The selective medium had the same composition but was supplemented with 15 g of NaCl per liter. The injury and lethality were analyzed of heat treatment of spores of four Bacillus cereus strains in phosphate buffer and in mechanically separated poultry meat. The four strains tested exhibited great differences in injury and death rates, and considerable differences could be observed in survivor counts when spores were suspended in buffer or in meat. Moreover, variability in behavior when the strains were heat treated in buffer could not be extrapolated to the same strains suspended in food. These data showed that it is necessary to be very careful when evaluating potential hazards from B. cereus spores in various foods; heating medium and strain selection must be considered to evaluate the efficiency of heat treatments.