Comparison of fisetin and quercetin oxidation with a cell‐free extract of onion trimmings and peel,plant waste,containing peroxidase enzyme: a further insight into flavonol degradation mechanism

A peroxidase‐active, cell‐free extract prepared from onion solid wastes was studied with regard to its biocatalytic properties, using fisetin (3,3′,4′,7‐tetrahydroxyflavone) as substrate. This particular substrate was selected to investigate specifically the role of the A‐ring of the flavonol skeleton in the oxidisability and cleavage pathway(s), and ascertain whether changes in substitution pattern may affect product formation, compared with quercetin (3,3′,4′,5,7‐pentahydroxyflavone). Oxidation was shown to be optimum at pH values between 5 and 7 and temperatures between 20 and 40 °C. HPLC analyses of a fisetin solution treated with the cell‐free extract revealed the formation of three major products, including 3,4‐dihydroxybenzoic acid (protocatechuic acid), 2,4‐dihydroxybenzoic acid (β‐resorcylic acid) and the depside 2‐(3,4‐dihydroxybenzyloxy)‐4‐dihydroxybenzoic acid. The tentative identification of these substances permitted an approach to a putative oxidation pathway, which appeared to have important similarities with that of quercetin.     

Finishing steers with diets based on corn, high-tannin sorghum or a mix of both: Color and lipid oxidation in beef

We tested the hypothesis that feeding high-tannin sorghum (HTS) to steers would produce beef more resistant to oxidative deterioration. We observed lower thiobarbituric acid-reactive substances (TBARS) in Gluteus medius of steers fed HTS before it was displayed (P=0.028), which could be explained by a reduced response to stress in these animals. While steers finished with corn and corn+HTS had elevated plasma cortisol at the end of the feeding period (P=0.047 and 0.093, respectively), animals fed HTS and corn+vitamin E did not. However, feeding HTS increased the rate of discoloration and TBARS accumulation after aerobic display of Longissimus lumborum and Gluteus medius. Diet did not affect the activity of oxidation-related enzymes and fatty acid composition of muscle. The accelerated rate of lipid oxidation during display of beef could be partially explained by a numerically lower concentration of tocopherols in the tissue.     

Morphology and physico-chemical properties of Bacillus spores surrounded or not with an exosporium: Consequences on their ability to adhere to stainless steel

This study was designed to elucidate the influence of spore properties such as the presence of an exosporium, on their ability to adhere to materials. This analysis was performed on 17 strains belonging to the B. cereus group and to less related Bacillus species. We first demonstrated that spores of the B. cereus group, surrounded by an exosporium, differed in their morphological features such as exosporium size, number of appendages or hair-like nap length. We also found that the saccharidic composition of exosporium differed among strains, e.g. concerning a newly identified rhamnose derivative: the 2,4-O-dimethyl-rhamnose. Conversely, spores of distant Bacillus species shared morphological and physico-chemical properties with B. cereus spores. Some external features were also observed on these spores, such as a thin loose-fitting layer, whose nature is still to be determined, or a thick saccharidic layer (mainly composed of rhamnose and quinovose). The ability of spores to adhere to stainless steel varied among strains, those belonging to the B. cereus group generally being the most adherent. However, the presence of an exosporium is not sufficient to explain the ability of spores to adhere to inanimate surfaces. Indeed, when the 17 strains were compared, hydrophobicity and the number of appendages were the only significant adhesion parameters. Furthermore, the differences in spore adhesion observed within the B. cereus group were related to differences in the number of appendages, the exosporium length and to a lesser extent, the zeta potential.     

The fabrication of a novel film based on polycaprolactone incorporated with chitosan and rutin: potential as an antibacterial carrier for rainbow trout packaging

Food Science and Biotechnology - Rutin and chitosan could be utilized in the food industry owing to their antioxidant and antibacterial properties. This study was carried out to fabricate novel...     

Improvement of the commercial quality of chilled Norway lobster (Nephrops norvegicus) stored in slurry ice: Effects of a preliminary treatment with an antimelanosic agent on enzymatic browning

The use of slurry ice is gaining increasing importance as an advanced method for the hygienic and efficient chilling and sub-zero storage of aquatic food products. In this work, this technology was applied as a novel technique for the chilling and storage of Norway lobster (Nephrops norvegicus) – a crustacean species of high-commercial value – under refrigeration conditions at −1.5 °C. In addition, the effects of a preliminary treatment with 0.5% Na HSO₃ on surface browning were evaluated and compared with the results obtained in control batches not subjected to such treatment. The processing of lobster in slurry ice significantly (p < 0.05) slowed down microbial spoilage, as determined by the counts of aerobes, psychrotrophs, proteolytic bacteria, and lactose-fermenting Enterobacteriaceae, and by the formation of volatile amines. Likewise, the autolytic breakdown mechanisms – as determined by the K value – were also significantly (p < 0.05) inhibited in the slurry ice batch. Remarkably, preliminary treatment with 0.5% sodium metabisulphite permitted better maintenance of the parameters involved in sensory quality – especially as regards the aspect of the carapace – as compared with non-treated batches, and allowed a shelf life of 9 days without surpassing the 150 mg/kg legal limit established for this food additive. On contrast, the non-treated batch stored in slurry ice exhibited a shelf life of 5 days. The combination of technological treatments proposed in this work – preliminary antimelanosic treatment and storage in slurry ice – may be successfully applied to other fresh and frozen shellfish species with a view to extending shelf life and to avoiding the legal and toxicological problems derived from current abuse of such antimelanosic agents to prevent shellfish browning.