M.C. Vidal-Carou

Safety properties and molecular strain typing of lactic acid bacteria from slightly fermented sausages

Aim:u2002 To evaluate the biodiversity of lactobacilli from slightly fermented sausages (chorizo, fuet and salchichon) by molecular typing, while considering their safety aspects.

Determination of ATP related compounds in fresh and canned tuna fish by HPLC

Abstract Reliability of two HPLC methods to determine ATP, ADP, AMP, IMP, inosine and hypoxanthine in fish was studied after modifying mobile phase composition to improve resolution. Both methods included the same extraction procedure, and used a C18 column and UV detection. Mobile phases were neutral phosphate buffer in both methods but one of them used tetrabutylammonium hydrogen sulphate as ionic supressor. Both procedures gave acceptable results, although the addition of the ionic suppressor led to various advantages, such as improved recovery, precision, and sensitivity. Furthermore, chromatographic procedure without ionic suppressor showed a lack of specificity in canned tuna samples, since an unknown peak appeared at ATP retention time. In addition, IMP, Ino and Hx stability in fish samples and in fish samples extracts stored at -18 °C were studied and no changes on their contents were observed throughout 26 weeks.

Histamine and tyramine in meat products: relationship with meat spoilage.

Abstract Biogenic amines in processed meat products can be useful as indices of poor-quality raw material, but they can also be related with microbial activity involved in fermentation processes. This paper provides new data on this topic. Histamine, tyramine and pH changes were followed during storage/spoilage of beef and pork at both room and refrigerated temperatures. A notable increase in the content of amines was observed at both temperatures studied. A greater and more rapid formation of histamine and tyramine took place in pork than in beef. The increase in the amines occurred before the increase in pH value. A preliminary study about the influence of ripening on histamine and tyramine contents was also carried out. This process seems to exert a greater influence on histamine than on tyramine content. Finally, the histamine and tyramine contents of 63 Spanish meat products were determined. Both amines were detected in all samples, but concentrations varied greatly. Uncooked and ripened meats showed statistically significant higher amounts of both amines than cooked meat products. In cooked meat products, histamine values ranged from 0·25 to 3·90 mg/kg and tyramine from 0·50 to 25·6 mg/kg. For uncooked and ripened meat products, the range of histamine was from 0·25 to 249 mg/kg and of tyramine from 0·45 to 510 mg/kg.

Reduction of Biogenic Amine Formation Using a Negative Amino Acid–Decarboxylase Starter Culture for Fermentation of Fuet Sausages

The ability of Lactobacillus sakei CTC494, a negative amino acid-decarboxylase starter culture, to reduce biogenic amine accumulation during sausage fermentation and storage at 4 and 19 degrees C was studied. The effect on the amine formation of the tyramine producer Lactobacillus curvatus CTC371, as a positive strain, was also examined in comparison to a spontaneous fermentation process without starter culture (control batch). The polyamines spermine, spermidine, and diaminopropane were not influenced by the ripening, and their levels slightly decreased in all the batches throughout the storage. Tyramine, cadaverine, and putrescine were the main amines formed during the ripening. The addition of starter culture resulted in a decrease on the biogenic amine formation, depending on the strain inoculated. A great reduction in tyramine content was achieved when L. sakei CTC494 was inoculated, whereas L. curvatus CTC371 only attenuated tyramine accumulation compared with the control batch. Both starters were able to significantly limit the production of putrescine and cadaverine, and they inhibited tryptamine and phenylethylamine formation by the wild microbial flora. Tyramine levels of the control sausages rose during the storage at both temperatures, whereas those of cadaverine only increased at 19 degrees C. On the contrary, sausages manufactured through the starter controlled fermentation did not show changes of amine contents during the storage. The addition of a proper selected starter culture is advisable to produce safer sausages with low contents of biogenic amines.

Histamine and tyramine in spanish wines: Relationships with total sulfur dioxide level, volatile acidity and malo-lactic fermentation intensity

Abstract Histamine and tyramine contents in 226 and 186 Spanish wine samples, respectively, have been studied employing spectrofluorometric methods. The average content of histamine in red wines (4·07 mg/liter) proves to be higher than in white wines (0·81 mg/liter) and rose wines (0·86 mg/liter). The average content of tyramine was also higher in red wines (3·03 mg/liter) than in white (1·49 mg/liter) and rose ones (1·66 mg/liter). Relationships are studied between the contents of these amines and that of total sulfur dioxide and volatile acidity, as well as with the intensity of malo-lactic fermentation. Our results, in general, show that (a) the highest levels of both amines occur in red wines with low concentrations of total sulfur dioxide, (b) white and rose wines with high volatile acidity show higher levels of these amines than wines with low volatile acidity, and (c) in all wines highest levels of amines correspond to wines with a stronger malo-lactic fermentation.

Changes in Biogenic Amines during the Manufacture and Storage of Semipreserved Anchovies

Biogenic amines were determined by using high-pressure liquid chromatography during spoilage of raw Engraulis encrasicholus (anchovies), during ripening and shelf life. Histamine, cadaverine, tyramine, and putrescine were extensively formed at the beginning of spoilage, while β-phenylethylamine and tryptamine were formed only at advanced stages of spoiling. Serotonin, spermine, and spermidine levels were constant throughout spoilage. Seventeen lots of anchovies were evaluated through the typical ripening process. Each ripening process lasted 18 to 22 weeks, Only a slight formation of biogenic amines was observed during the first period of ripening (2 to 4 weeks). According to our results, ripening had little influence on the formation of amines, and therefore the amount of amines in the final products depends primarily on the levels of these substances in the raw material. During shelf-life studies, anchovies packed in brine were more stable, from the point of view of biogenic amine formation, than anchovies packed in oil. High formation of tryptamine and histamine was observed in both products when they were stored at room temperature. Refrigerated storage prevents amine formation.

Fast simultaneous determination of free and conjugated isoflavones in soy milk by UHPLC-UV.

Ultra high pressure liquid chromatography (UHPLC) has become a widely used technique in separation science as it can shorten analysis time while maintaining resolution and increasing sensitivity. Here we developed a UHPLC method with UV detection for the simultaneous determination of isoflavone aglycones (daidzein, glycitein and genistein), their corresponding glycoside forms (daidzin, glycitin and genistin), and acetyl and malonyl conjugate forms of glycosides (malonyldaidzin, malonylglycitin, malonylgenistin, acetyldaidzin, acetylglycitin, acetylgenistin) in soy milk. The method allowed reliable determinations of 12 isoflavones in less than 8 min of chromatographic elution. It provided a satisfactory linearity ranging from 0.1 to 5mg/L, except for daidzin and genistin, for which it ranged from 0.1 to 10mg/L. In addition, it showed acceptable chromatographic sensitivity, with a detection limit lower than 0.05 mg/L and a determination limit below 0.2mg/L. The precision, in terms of relative standard deviation, was lower than 5% and the accuracy, as mean recovery, was greater than 95%. Total isoflavone content in commercial soy milk samples (n=8) ranged from 1805.22 to 3195.59 mg/kg dw. Genistin and Daidzin were the major isoflavones in all samples. The proportion of aglycones, ß-glucosides, and acetyl and malonyl glucosides differed among the samples. ß-Glucosides were identified as the predominant forms.

Biogenic amine index for freshness evaluation in iced mediterranean hake (Merluccius merluccius)

Biogenic amine accumulation was studied during the ice storage of Mediterranean hake. Sensory analysis and counts of Shewanella, Pseudomonas, enterobacteria, psychrotrophic, and mesophilic bacteria provided complementary information on hake spoilage. Putrescine and cadaverine were the main amines accumulated, whereas histamine and tyramine were minor amines but had qualitative interest from the hygienic point of view. Although all biogenic amines were less abundant than in pelagic fish, they may also be used as indicators of freshness and/or spoilage in hake. Cadaverine was the amine best correlated with Shewanella, which was the specific spoilage organism. Therefore, cadaverine may be regarded as the specific spoilage biogenic amine for hake stored at chilling temperatures. However, the biogenic amine index, which considers cadaverine, putrescine, histamine, and tyramine, has several advantages as an indicator of hake quality. Taking into account sensory data, an acceptability limit of the biogenic amine index could be established in 15 to 20 microg/g.

Validation of a gas-chromatographic method for volatile amine determination in fish samples

Abstract A gas-chromatographic (GC) procedure is described for the determination of volatile amines in fish. The method includes a first step of volatile amine extraction with 0.6 N perchloric acid, followed by alkalinization with 65% ( w w ) KOH and a subsequent toluene extraction. Dimethylamine (DMA) and trimethylamine (TMA) were well resolved; moreover, monomethylamine (MMA) did not interfere in the determination of DMA and TMA, and can also be useful in assessing spoilage of crustaceans. The suitability of toluene as a solvent for extraction is demonstrated. Linearity, precision and recovery were satisfactory. Sensitivity limits were lower than 0.038, 0.110 and 0.167 mg N per 100 g for TMA, DMA and MMA, respectively. In addition, contents of DMA and TMA in fresh and frozen hake samples were studied.

Histamine, cadaverine, and putrescine produced in vitro by enterobacteriaceae and pseudomonadaceae isolated from spinach.

A total of 364 bacterial isolates, obtained from spinach leaves, were assayed in a decarboxylase broth containing histidine, lysine, and ornithine to check their ability to produce biogenic amines, and then quantified by high-performance liquid chromatography. Among these isolates, 240 formed cadaverine, 208 formed putrescine, and 196 formed histamine, in widely varying amounts. They frequently produced more than one biogenic amine. Klebsiella pneumoniae subsp. pneumoniae and Morganella morganii were the main histamine producers, with mean values of 1,600 and 2,440 mg/liter, respectively, followed by Pantoea spp. 3 (1,710 mg/liter) and Hafnia alvei (2,500 mg/liter). Enterobacter amnigenus and Enterobacter cloacae produced particularly high amounts of putrescine, with mean values of 2,340 and 2,890 mg/liter, respectively. The strongest cadaverine formation was shown by Serratia liquefaciens (3,300 mg/liter), Serratia marcescens (3,280 mg/liter), and Stenotrophomonas maltophilia (1,000 mg/liter).