New solvent systems for thin-layer chromatographic determination of nine biogenic amines in fish and squid

Different solvent systems were evaluated for their ability to separate biogenic amines by thin-layer chromatography (TLC). Dansyl derivatives of agmatine, putrescine, tryptamine, cadaverine, spermidine, histamine, spermine, tyramine and beta-phenylethylamine were separated using the solvent system chloroform-diethyl ether-triethylamine (6:4:1), followed by chloroform-triethylamine (6:1). After separation dansyl amines were quantified by fluorescence densitometry at 330 nm. Correlation coefficients of linear regressions were higher than 0.99 for all amines, except for agmatine (0.976). Detection limits were 10 ng for tryptamine, tyramine, histamine and beta-phenylethylamine, and 5 ng for the other amines. The overall repeatability of the chromatography was 1.82% when including agmatine and barely 1.02% for the other amines. The accuracy ranged from 105.97% (agmatine) to 49.92% (tryptamine). This thin-layer chromatography method was found to be an effective and precise analytical procedure to separate and determine biogenic amines. Its main advantages compared to previous procedures are that it uses less harmful solvent (diethyl ether instead of benzene) and can separate a larger group of biogenic amines. (C) 2004 Elsevier B.V. All rights reserved.10454167122323

AN ALTERNATIVE APPROACH FOR IMPROVING FRESHNESS INDICES FOR SQUID (LOLIGO PLEI)

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)The leaching of soluble compounds reduces the efficiency of chemical indices for freshness when fish is stored in ice. The objective of this study was to evaluate whether chemical indices for freshness evaluation of squid (Loligo plei) could be improved by expressing their contents as percentages of the non-protein nitrogen (NPN). The contents of NPN, free amino groups (FAG), trimethylamine oxide (TMA-O), trimethylamine (TMA), volatile basic nitrogen (VBN), ammonia (AMM), urea and free tryptophan (FT) were periodically determined in squid muscle during 16 days of storage in ice. The VBN, AMM, TMA, urea and FT contents in squids, when expressed as mg/100 g, did not distinguish between squids stored in ice for 1 or 2 weeks. However, when the contents of VBN and AMM were expressed as percentages of the NPN, it was possible to distinguish between squids stored for 1, 4 and 7 days. Free tryptophan was the most efficient quality index for L. plei, allowing accurate discrimination of squids stored in ice for 0-2, 4, 7-10, 13 and 16 days.423437450Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)FAPESP [0521-6

Chemical and microbial analyses of squid muscle (Loligo plei) during storage in ice

Chemical and microbial changes in squid muscle (Loligo plei) and the efficiency of chemical indices for freshness evaluation were investigated during storage in contact ice (CI) and non-contact ice (NC). Psychrotrophic bacterial counts and non-protein nitrogen, free amino acids, trimethylamine, volatile basic nitrogen (VBN), urea and free tryptophan contents were periodically determined in squid muscle. No difference (P < 0.05) was detected between treatments regarding the increase of psychrotrophic bacterial counts in squid muscle during storage. The leaching of soluble compounds in Cl treatment drastically affected the efficiency of the chemical indices for freshness. Trimethylamine and VBN contents in squid muscle increased only after day 9 and no increase was observed in free tryptophan and urea contents in Cl treatment. In the NC treatment the contents of VBN and trimethylamine slowly increased during the first days of storage whereas free tryptophan and urea contents markedly increased during the whole storage. Free tryptophan and urea can be useful freshness indices for L. plei in storage conditions wherein leaching have been minimized. (C) 2004 Elsevier Ltd. All rights reserved.91347748

Sensory, colour and psychrotrophic bacterial analyses of squids (Loligo plei) during storage in ice

The after catch quality decrease of squid, Loligo plei, was evaluated, comparing two storage treatments: contact and non-contact with ice. he squids were evaluated for their sensory, inistrumental colour and psychrotrophic bacterial count changes. A principal component analysis of the sensory data indicated that the squid quality markedly decreased after 7 days of storage, in both treatments. The instrumental colour analysis showed that the red and yellow colours of the squid skin increased with time in both treatments, while in the muscle, the intensify of the red and yellow colours increased more in the non-contact than in the contact with ice treatment. The results of the sensory and instrumental colour analyses were highly correlated, both being adequate for squid quality evaluation. The storage methods did not affect the development of bacterial counts, which in both treatments were below 10(6) cfu/g of muscle after 16 days of storage. The results showed that in both treatments the end of the shefl-life of L, plei squid was determined by the loss of its sensory quality. The packaging of the squids resulted in more intense changes in the characteristic colour of the squid muscle, and did not promote a significant reduction in microbial growth. Thus the non-contact ice storage method presented no advantages when compared with the contact ice storage method with respect to the quality preservation of L. plei tinder laboratory conditions. (C) 2002 Elsevier Science Ltd.351212