Determination of volatile compounds to characterize fish spoilage using headspace/mass spectrometry and solid‐phase microextraction/gas chromatography/mass spectrometry

Changes in volatile compounds were monitored in whiting (Merlangius merlangus), cod (Gadus morhua) and mackerel (Scomber scombrus) and related to spoilage. Data are presented from headspace/mass spectrometric (HS/MS) analysis and solid‐phase microextraction/gas chromatographic/mass spectrometric (SPME/GC/MS) analysis at two time points (day 0 and day 10) during storage at 4 °C. HS/MS revealed 24 ions that could be used as markers of spoilage. SPME/GC/MS identified 86 compounds, 20 of which could perhaps be used to characterize freshness: principally alcohols, ketones, aldehydes and C₂–C₁₁ esters. Compounds common to the three species studied appear to be generated by microbial degradation. Copyright © 2005 Society of Chemical Industry     

Variation in content of tyramine,histamine, 2-phenylethylamine,tryptamine and their precursor amino acids in a Chardonnay wine by using different commercial active dry yeasts and nitrogen sources

Wine is a fermented beverage that could be affected by high concentrations of biogenic amines, thus altering organoleptic and health properties. In this work, the capacity of different selected yeast strains regarding to affect the content of tyramine, histamine, 2-phenylethylamine, tryptamine and their precursor amino acids (pAA) during fermentation has been described. Overall, biogenic amines (BAs) and pAA contents appeared significantly related both to the strain and to the nutrient supplementation applied. Among BAs, without and (with) nitrogen source addition, the concentrations covered a range between 0.1 and 9.5 (0.1–10.3) mg L⁻¹ for tyramine; 0.1 and 4.4 (0.1–4.6) mg L⁻¹ for histamine; 0.4 and 1.1 (0.4–1.4) mg L⁻¹ for 2-phenylethylamine; and 0.02 and 0.14 (0.01–0.12) mg L⁻¹ for tryptamine, respectively. Considering that also wine yeast species are responsible for BAs formation, the evidence from fermentation trials underlined the relevance of a careful choice of ADY strains and nitrogen sources in the management of alcoholic fermentation in wine.     

离交色谱法提取废蜜中糖分

介绍一种离子交换色谱法分离废蜜中的糖分，利用该技术可将废蜜含糖由2％甜菜降至0．25％甜菜，糖份回收率由83％提高到95％。生产过程中树脂不用再生，无废水排放。     

Hydrogen peroxide concentration measured in cultivation substrates during growth and fruiting of the mushrooms Agaricus bisporus and Pleurotus spp.

Hydrogen peroxide is suspected of being highly implicated in mushroom nutrition and in substrate bleaching during cultivation. The parameters for measuring H₂O₂ in compost samples were examined and the methodology was applied to samples from both compost colonized by cultivars and wild isolates of Agaricus bisporus, and wheat straw or coffee pulp colonized by Pleurotus spp. Laccase and peroxidase activities were also measured. H₂O₂ concentration measured after heating at 80 °C for inactivating laccases and peroxidases was probably both H₂O₂ pre‐existing in the compost and H₂O₂ generated from quinones and active oxygen species. This potential H₂O₂ concentration increased during the vegetative growth for all the strains, in agreement with a direct relationship between H₂O₂ concentration and active biomass of A. bisporus or Pleurotus spp. in their cultivation substrates. Correlations were observed between H₂O₂ concentration and manganese peroxidase activity in cultivation substrates at the stage of primordia formation. At this stage of development, H₂O₂ generation via biotic or abiotic mechanisms should be an important physiological trait of mushrooms. Copyright © 2007 Society of Chemical Industry     

Effect of genotype,maturity stage and post‐harvest storage on phenolic compounds,carotenoid content and antioxidant capacity,of Andean mashua tubers (Tropaeolum tuberosum Ruiz & Pavón)

The total phenolics, anthocyanins, flavan 3‐ols, carotenoids and antioxidant capacity of mashua (Tropaeolum tuberosum Ruiz & Pavón) tubers from 10 yellow and purple cultivars were determined at different maturity stages (5–7.5 months after planting) and sunning post‐harvest storage periods (7–35 days). Both the antioxidant capacity (ORAC and ABTS assays) and the content of the bioactive compounds tested varied markedly between cultivars. Purple varieties reached the highest antioxidant capacity during tuber development (271–446 µmol Trolox equiv g^?1 DM, ORAC assay). The kinetics of accumulation or disappearance of the bioactive compounds tested during maturation was dependent both on the cultivar and on the compound considered. For anthocyanins, there was a marked increase during maturation in all the purple cultivars. During the sunning post‐harvest storage, the changes in antioxidant capacity (ABTS assay) and content of the bioactive compounds tested also varied between cultivars. A marked decrease in anthocyanins was observed for the anthocyanin‐containing cultivars. In general, the correlation between antioxidant capacity and the content of bioactive compounds varied markedly between cultivars. Antioxidant capacity in purple varieties correlated with total phenolics or flavan 3‐ols while only in some yellow varieties antioxidant capacity correlated with total phenolics. Copyright © 2007 Society of Chemical Industry