Ana Lúcia Leite Moraes

Produção de isomaltulose a partir da transformação enzimática da sacarose, utilizando-se Erwinia sp D12 imobilizada com alginato de cálcio

The glucosyltransferase of Erwinia sp D12 is able to convert sucrose into isomaltulose (6-0-a-D-glucopyranosyl-D-fructofuranose), an alternative sugar which presents low cariogenic potential, and can be used to produce chocolate, chewing gum and candy. The isomaltulose is also used to produce isomalt, a mixture of alcohol-sugar with a low caloric value and low cariogenicity power. In the study of the influence of the components of the culture medium in the glucosyltransferase production in flasks under shaking conditions, the highest activity (12.8 units of activity /mL of culture medium) was obtained in culture medium A, containing molasses 12% (p/v) of the total soluble solid, peptone 4% (p/v) and meat extract 0,4% (p/v). In the study of the effects of time and temperature on the fermentation of Erwinia sp D12 in a 3L New Brunswick fermentor containing culture medium A. the highest glucosyltransferase activity (15.6 units of activity /mL of culture medium) was obtained during the exponential growth phase after 8 hours of fermentation at 30oC. In the production of isomaltulose from enzymatic transformation of sucrose by Erwinia sp D12 cells immobilized in calcium alginate, the effects of the temperature (25-35oC) and substrate concentration (12,5-60%) were evaluated, the yield of isomaltulose was approximately 50%, from sucrose solutions ranging from 20 to 30% at 35oC. Excess of sucrose affected the activity of the immobilized cell, decreasing conversion of sucrose into isomaltulose. The syrup obtained was purified through Ion Exchange Chromatography, and the crystallization of eluent by the decreasing temperature. The obtained crystals presented 91,39% of isomaltulose.SUMMARY PRODUCTION OF ISOMALTULOSE FROM ENZYMATIC TRANSFORMATION OF SUCROSE, USING Erwinia sp D12 IMMOBILIZED WITH CALCIUM ALGINATE. The glucosyltransferase of Erwinia sp D12 is able to convert sucrose into isomaltulose (6-0-α-D-glucopyranosyl-Dfructofuranose), an alternative sugar which presents low cariogenic potential, and can be used to produce chocolate, chewing gum and candy. The isomaltulose is also used to produce isomalt, a mixture of alcohol-sugar with a low caloric value and low cariogenicity power. In the study of the influence of the components of the culture medium in the glucosyltransferase production in flasks under shaking conditions, the highest activity (12.8 units of activity /mL of culture medium) was obtained in culture medium A, containing molasses 12% (p/v) of the total soluble solid, peptone 4% (p/v) and meat extract 0,4% (p/v). In the study of the effects of time and temperature on the fermentation of Erwinia sp D12 in a 3L New Brunswick fermentor containing culture medium A. the highest glucosyltransferase activity (15.6 units of activity /mL of culture medium) was obtained during the exponential growth phase after 8 hours of fermentation at 30oC. In the production of isomaltulose from enzymatic transformation of sucrose by Erwinia sp D12 cells immobilized in calcium alginate, the effects of the temperature (25–35oC) and substrate concentration (12,5–60%) were evaluated, the yield of isomaltulose was approximately 50%, from sucrose solutions ranging from 20 to 30% at 35oC. Excess of sucrose affected the activity of the immobilized cell, decreasing conversion of sucrose into isomaltulose. The syrup obtained was purified through Ion Exchange Chromatography, and the crystallization of eluent by the decreasing temperature. The obtained crystals presented 91,39% of isomaltulose.

Características microbiológicas e físico-químicas do leite de cabra submetido à pasteurização e ao congelamento, comercializado na cidade de Alfenas-MG doi: http://dx.doi.org/10.5892/ruvrv.2013.111.224233

Demand for goat milk has increased in Brazil along the years. This food represents a high quality protein and calcium resource besides being an alternative for individuals who are allergic to cow milk. However, it is highly susceptible to contamination and subjected to fraud. Therefore, this paper was aimed at verifying the quality of goat milk commercialized in Alfenas, Minas Gerais, and at evaluating the effect of pasteurization and of freezing on its microbiological and physicochemical characteristics. Microbiological and physicochemical analysis were carried out in three lots of raw, pasteurized and pasteurized-frozen goat milk for 90 days, during 9 months, a milk-lot being purchased every 90 days. Data obtained underwent analysis of variance and Turkey test (p<0.05). It was observed that pasteurization was efficient to improve microbiological quality of milk, which was kept by freezing. Physicochemical characteristics were in accordance with legislation and pasteurization and freezing for 90 days did not alter them. It was concluded that goat milk commercialized in Alfenas, Minas Gerais presents microbiological and physicochemical qualities within the standards established by legislation and that pasteurization and freezing did not interfere with those qualities.

Escurecimento enzimático: uma aula prática

This paper presents a practical class about the enzymes polyphenol oxidases, which have been shown to be responsible for the enzymatic browning of fruits and vegetables. Vegetables samples were submitted to enzymatic inactivation process with chemical reagents, as well as by bleaching methods of applying heat by conventional oven and microwave oven. Process efficiency was assessed qualitatively by both observing the guaiacol peroxidase activity and after the storage period under refrigeration or freezing. The practical results obtained in this class allow exploring multidisciplinary knowledge in food science, with practical applications in everyday life.