New Researches in Biotechnology - Facultatea de Biotehnologii ...

Proceeding of the 4 rd International Symposium“NEW RESEARCH IN BIOTECHNOLOGY” USAMV Bucharest, Romania, 2011(manometric method). These tests were made using Lyssy L80-5000 water vaporpermeability tester and Lyssy L100-5000 manometric gas permeability tester both fromPBI Dansensor.Physico-chemical analysesWater activity was determined at baseline, before the washing process, and that onevery testing day, using the Aquaspector AQS-2-TC device.Homogeneous samples were obtained by cutting the lettuce leafs with a sterilescalpel.Evidence of weight loss as a result of dehydration vegetables during storage wasdetermined by weighing with the electronic balance Kern EW1500-2M. Salads were firstweighed.To determine the pH 10g of homogeneous sample were weighed, then 100mLdistillated water were added. It was used the Inolab pH meter with combined electrode andthe samples were homogenized using a Circular Seward 400 Stomacher.Microbiological analysesSamples were initially analyzed, after the washing process, considered day 0, andthen on day 1, 3, 5, 7 and 10. For the microbiological analyses, 10g of lettuce were weighedand then homogenized with 90mL peptone water using the Circular Seward 400 Stomacherfor 30 seconds. Serial dilutions (1:10) of each homogenized sample were made. Totalaerobic mesophiles and psychrotrophs were determined according to SR EN ISO4833/2003, using Plate Count Agar (PCA, Biokar Diagnostics) and incubated at 30°C for 3days. The yeasts and moulds were determined according to SR ISO 21527-1/2009, usingDichloran-Rose Bengal Chlormaphenicol agar (DRBC agar, Biokar Diagnostics), incubatedat 25 °C for 5 days. Coliform bacteria were determined using Violet Red Bile Agar withLactose, VRBL (Biokar Diagnostics) – incubated 24h at 37 °C STAS ISO 4832/2009.Escherichia coli was determine according to SR ISO 16649-2/2007 using Tryptone BileGlucuronide, TBX (Lab M Harlequin) – incubated 24h at 44 °C.Sensory qualityThere were evaluated changes in visual quality, texture, flavour, off-odours andbrowning.1583. RESULTS AND DISCUSSIONSBarrier properties analysisThe barrier properties to water vapor and gas (oxygen, nitrogen and carbondioxide) are presented in Table 1.Effect of storage on water lossIn terms of water activity, there was neither significant difference betweenthe salads packaged in different film bags, and the perforations didn’t have any significantrelevance. The initial lettuce water activity, at baseline, before washing, was 1.023. Thevalues registered on the testing days are listed in table 1.The lowest water activity values were registered for sample 1, especially in thefirst days of storage. In fig. 1 there can be observed that all the tested lettuce samplesregistered an increase of the water activity values in the first 3 days, reaching the maximum