QUALITY LOSS of DOUBLE CONCENTRATED TOMATO PASTE: EVOLUTION of the MICROBIAL FLORA and MAIN ANALYTICAL PARAMETERS DURING STORAGE AT DIFFERENT TEMPERATURES

This study deals with nonsterile canning of double concentrate tomatoes (approximately 30 degrees Brix) stored for 210 days at three different temperatures (4, 10 and 25C) in 200 kg drums. The evolving analytical composition (soluble solids, total solids, glucose, fructose, pH, total acidity, volatile acidity, citric acid, malic acid, succinic acid, hydroxymethylfurfural (HMF) and color parameters) that the product underwent during storage was dependent both on storage temperature and on different aerobic levels within the drum (top and bottom sections). The microbial profile (yeast, lactic acid bacilli and molds) was correlated with many important metabolites (D- and L-lactic acids, ethanol, acetic acid and diacetyl). The results indicate that the increase of these substances is dependent both on storage temperature as well as the oxygen tension within the drums. Taken all together, the analytical findings offer a great help in evaluating the quality of semifinished tomatoes. We also found that lactic bacteria grow rapidly at 25C and after 15 days their number from both sampling areas in the drums (i.e., 10 cm below the sample surface and 15 cm above the bottom of each drum) is already greater than 10(5) cfu/ml. At 10C, 30 days were needed to reach such a cell concentration, and after 45 days the level reaches 10(7)-10(8) cfu/ml. By contrast, at 4C there were differences between top and bottom sampling areas. In the top area, 10(5) cfu/ml was reached after 60 days, while for the bottom area this was reached after 120 days. Regarding yeast at 25C, the cfu/ml values were 10(5)-10(6) in both areas of the drum after the 60th storage day. At 10C the behavior was the same: about 10(5) cfu/ml had been found after 30 days. Finally at 4C the yeast reach 10(5) cfu/ml after 45 days in both sampling areas. Regarding mold, no growth in the sampling areas was seen.