EFFECTS OF ORGANIC ACIDS, NISIN, LYZOZYME AND EDTA ON THE SURVIVAL OF YERSINIA ENTEROCOLITICA POPULATION IN INOCULATED ORANGE BEVERAGES

Inactivation of a Yersinia enterocolitica strain by 3.4% ascorbic acid (AA), 0.5% citric acid (CA), 0.2% lactic acid, 100 IU/mL nisin, 2,400 IU/mL lysozyme and 20 mM ethylenediaminetetraacetic acid disodium salt (EDTA ), alone and combined, was studied at different temperatures (4 and 25C) in commercial and laboratory-prepared orange beverages. In laboratory-prepared juice, highest reductions (between 3.06 and 4.07 log units) were obtained with acid mixtures at 25C after 20 min of incubation. At 24 h of incubation, EDTA was bactericidal and the mixtures with nisin or lysozyme resulted in count reductions of 6.03 and 5.98 log units, respectively. In commercial orange beverage, AA and CA gave reductions of 5.43 and 4.26 log units, respectively. The three acid mixtures were bactericidal within the first 10 min. EDTA alone or mixed completely inhibited Y. enterocolitica strain at 6 and 24 h of incubation. At 4C, all the results were significantly lower than at 25C.

PRACTICAL APPLICATIONS

Yersinia enterocolitica is a common cause of gastrointestinal disorders and may lead to sequelae. This pathogen can maintain its virulence in a wide temperature range and under adverse conditions such as pH lower than 4. There are reports describing the isolation of Y. enterocolitica from water and ice in Brazil and Latin America. The sale of unpasteurized drinks is a common practice in our region and their consumption has increased over the past years. In the present work, chemical compounds and biological inhibitors were studied. Some of these compounds showed to be efficient for reducing Y. enterocolitica populations. Furthermore, they did not modify the organoleptic characteristics of the beverages and they are not toxic for human beings.     

MUSCLE AND ROE LIPID COMPOSITION IN DIPLOID AND TRIPLOID SCALLOPS

The use of triploid bivalves is now common in the market. We tested if there was a difference in lipid and long-chain highly unsaturated fatty acid (HUFA) accumulation in the muscle of diploid and triploid scallops ( Argopecten ventricosus ) during maturation, as triploids do not reproduce and lipids are not transferred to the gonad, and thus, could be accumulated in the meat (adductor muscle). Differences in triacylglycerols, phospholipids, esterified and free sterols, as well as HUFA in the reserves of gonads were found between diploid and triploid scallops. In contrast, no differences were found in the muscle for any of the lipid classes or fatty acid content in relation to ploidy, although they varied in relation to the sampling month.

PRACTICAL APPLICATIONS

The results obtained indicate that for human consumption purposes, the quality of the meat and roe of scallops follows a temporal pattern of lipid accumulation, with higher levels of total sterols in summer, but a higher proportion of arachidonic acid in winter and lower docosahexaenoic acid in autumn, and that the muscle lipid composition is not affected by the triploid condition.     

THERMAL PROPERTIES OF PASSION FRUIT JUICE AS AFFECTED BY TEMPERATURE AND WATER CONTENT

The specific heat, thermal conductivity and density of passion fruit juice were experimentally determined from 0.506 to 0.902 (wet basis) water content and temperatures from 0.4 to 68.8C. The experimental results were compared with existing and widely used models for the thermal properties. In addition, based on empiric equations from literature, new simple models were parameterized with a subset of the total experimental data. The specific heat and thermal conductivity showed linear dependency on water content and temperature, while the density was nonlinearly related to water content. The generalized predictive models were considerably good for this product but the empiric, product‐specific models developed in the present work yield better predictions. Even though the existing models showed a moderate accuracy, the new simple ones would be preferred, because they constitute an easier and direct way of evaluating the thermal properties of passion fruit juice, requiring no information about the chemical composition of the product, and a reduced time of the estimation procedure, as the new empiric models are described in terms of only two physical parameters, the water content and the temperature.     

雨水生物过滤处理技术在澳大利亚的研究与应用

介绍了一种澳大利亚采用的雨水生物过滤处理技术。阐述了FAWB研究人员在系统构型、填料选择、植物选择种植及其净化效果等方面所取得的主要研究成果。针对雨水生物过滤处理技术在悬浮物、重金属离子和营养性污染物去除方面的优势,以及在系统构型方面有效储存雨水以回用的特色,提出可对该技术改进为我国的雨水处理系统研究和雨水处理构筑物设计所借鉴的建议。     

Effects of Chitosan on Yield and Compositional Data of Carrot and Apple Juice

Effects of chitosans on yield, titratable acidity, pH, soluble solids, and color of carrot and apple juice were evaluated. Carrots (Lange Rote Stumpfe) and apples (Golden Delicious) were treated with chitosan solutions (in 2% ascorbic acid) of two different concentrations and viscosities at 25°C between 0 and 120 min. The juices were obtained with a laboratory cage press following a standard program during 20 min. Treatments with chitosan produced no effect on juice yield but pH values and soluble solids were affected. Also chitosan treatment resulted in significant (P < 0.05) reduction of titratable acidity and color index. Reduction of β-carotene in carrot juice was also achieved and correlated with color index.