Biologically active amines in fermented and non-fermented commercial soybean products from the Spanish market.

Biologically active amines were determined in commercial soybean products. The antioxidant polyamines were found in both non-fermented and fermented soybean products. Natto and tempeh showed the highest content of polyamines (75-124 and 11-24 mg/kg of spermidine and spermine, respectively). On the other hand, the bacterial-related biogenic amines, tyramine, histamine, tryptamine and ß-phenylethylamine, were detected in practically all fermented products with a high variability. The highest contents were found in sufu, tamari and soybean paste. Extremely high tyramine and histamine contents, 1700 and 700 mg/kg, respectively, found in some sufu samples could be unhealthy. However, biogenic amines observed in the other soybean products should not be a risk for healthy consumers. However, individuals who take monoamine and diamine oxidase inhibitors drugs should be strongly recommended to avoid this kind of products in order to suffer no adverse health effects. These biogenic amines were not detected in non-fermented soybean products.

Isoflavone profile and protein quality during storage of sterilised soymilk treated by ultra high pressure homogenisation.

The application of ultra high pressure homogenisation (UHPH) treatments is useful to obtain fine and stable soymilk emulsions. Changes of isoflavones, protein digestibility and lysine availability during 4 months of storage at 20 ± 2°C in soymilk treated by UHPH (300 MPa and 75°C of inlet temperature) were studied in comparison to UHT-sterilised soymilk (142°C, 6s). Results indicated that although there was a significantly higher extractability of isoflavones in UHT (about 38%) than in UHPH-treated samples (about 15%), similar total contents were found at the end of storage. The interconversion of isoflavones into ß-glucosides was faster in UHT than in UHPH-treated soymilk. Similar evolution of protein digestibility in both UHPH and UHT-treated soymilks was found, being slightly higher in the initial UHT (88.4%) than in UHPH-treated samples (83.3%). No great differences were observed in the % of blocked lysine among samples after treatments, neither in their evolution throughout storage.

Changes of isoflavones and protein quality in soymilk pasteurised by ultra-high-pressure homogenisation throughout storage.

Ultra high pressure homogenisation (UHPH) is an emerging technology to obtain fine and stable soymilk emulsions. Very little information is available about the stability of this kind of product during storage. Changes of isoflavone profile, protein digestibility and lysine availability in pasteurised-UHPH soymilks were studied for 21 days at 4 °C in comparison to heat-pasteurised soymilks. Neither heat nor UHPH treatments affected the isoflavone profile, as the percentage of each chemical form, in comparison with unprocessed-soymilk. During storage, there was a conversion of isoflavone forms to aglycones, being higher in heat-processed samples. In addition, UHPH samples showed a lesser percentage of blocked lysine during storage. No differences were observed in the evolution of protein digestibility among samples. Therefore, UHPH treatment seems to produce a better product, due to lower amounts of aglycones, and higher protein nutritional quality than heat treatment.

Effect of ultra high pressure homogenization treatment on the bioactive compounds of soya milk.

Ultra high pressure homogenization (UHPH) is a useful novel technology to obtain safe and high-quality liquid foods. The effect of UHPH at 200 and 300 MPa in combination with different inlet temperatures (Tin) (55, 65 and 75 °C) on the bioactive compounds of soya milk was studied. Total phytosterols increased with the higher combination of pressure and temperature. The main phytosterol was ß-sitosterol, followed by stigmasterol and campesterol. Total tocopherols in UHPH-treated soya milks decreased as the temperature and pressure increased. UHPH treatment also affected the different chemical forms of tocopherols. No biogenic amines were detected in any of the analyzed soya milks. Meanwhile, the polyamines SPD and SPM were found in all soya milks, being stable to the UHPH treatment. Total isoflavones increased with the higher combination of pressure and temperature. No differences in the isoflavone profile were found, with ß-glucoside conjugates being the predominant form.

Identification of 5-hydroxymethyl-2-furfural (5-HMF) in Cava sparkling wines by LC-DAD-MS/MS and NMR spectrometry.

The aim of this study was to elucidate the structure of a potential ageing marker for Cava sparkling wine. In order to clarify the structure of this compound, NMR spectroscopy and hyphenated UHPLC-DAD-MS/MS techniques were used. We identified the hitherto unknown compound as 5-hydroxymethyl-2-furfuraldehyde (5-HMF). This is the first time that this compound has been reported in sparkling wines. A survey, based on the analysis of 80 commercial sparkling wines, showed that 5-HMF is present between 0.25 and 12.81 mg/L, and is compared with those reported for other types of wine. Hypothetical origin of 5-HMF in Cava sparkling wine is discussed.

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.

Influence of technological conditions of sausage fermentation on the aminogenic activity of L. curvatus CTC273.

The influence of technological factors (temperature and relative humidity of the manufacturing process and the diameter of the sausage) on the aminogenic activity of the strain Lactobacillus curvatus CTC273 was evaluated. Inoculation of sausages with L. curvatus CTC273 resulted in the accumulation of large amounts of biogenic amines (higher than 1000 mg/kg dry matter in some samples) during the manufacture of fuet and llonganissa sausages. Sausages produced via process 'A' (3 days at 20-23 °C and 90-95% RH followed by 20 days at 12-14 °C and 70% RH) contained significantly higher amounts (p < 0.05) of biogenic amines than those manufactured via process 'B' (23 days at 12-13 °C and 70-90% RH), specifically tyramine, cadaverine and phenylethylamine in llonganissa and phenylethylamine in fuet. The higher fermentation temperature and relative humidity during the fermentation stage in process 'A' promoted decarboxylase activity in L. curvatus CTC273 and thus favoured amine accumulation. The diameter of the sausages also influenced biogenic amine production. Higher amine levels were found (p < 0.05) in llonganissa than in fuet, regardless of the manufacturing conditions. The effect of the factors considered on the modulation of aminogenic activity is not necessarily linked to the effect of strain growth, but chiefly favouring proteolytic and decarboxylase reactions.

Validation of an ultra high pressure liquid chromatographic method for the determination of biologically active amines in food.

Biologically active amines include the so called biogenic amines, such as histamine, tyramine and cadaverine, and polyamines such as spermidine and spermine. Ultra high pressure liquid chromatography (UHPLC) is a new generation of separation techniques that takes full advantage of chromatographic principles to increase speed flow which drastically reduce analysis time. The aim of the present work was to validate a rapid method of UHPLC to detect the presence of biogenic amines and polyamines in food. Different food matrixes (wine, fish, cheese, and dry fermented sausage) were used in order to test the versatility of the method. The UHPLC method described in this article has been demonstrated as a reliable procedure to determine 12 biogenic amines and polyamines in less than 7min of chromatographic elution. The method provides a satisfactory linearity and chromatographic sensitivity with a detection limit lower than 0.2mg/L and a determination limit falling below 0.3mg/L for all amines. The precision, in terms of relative standard deviation, was lower than 5% and the accuracy, as mean recovery, was between 93% and 98%, depending on the food matrix.