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991.
Summary Thirty-two strains of starter cultures and lactic acid bacteria belonging to the genera Streptococcus, Leuconostoc and Lactobacillus were studied for their ability to produce acetoin (A) and diacetyl (D) from citrate and pyruvate added separately to skim milk and from pyruvate added to peptone-yeast extract-glucose broth (PYG).The largest amount of A + D was produced from citrate and by the citrate fermenters Streptococcus cremoris AM2, Str. faecalis, Leuconostoc citrovorum ATCC 8082, L. Gasei ATCC 393, L. Gasei ssp. alactosus and L. xylosus. Some strains of Str. cremoris, Str. thermophilus, some strains of L. Gasei, L. plantarum and L. coryniformis on the contrary produced more A + D from pyruvate than from citrate. Str. cremoris AM2 should be designated as Str. diaceticremoris like Str. diacetilactis.PYG was more favourable than skim milk for production of A + D from pyruvate by Str. lactis, some strains of Str. cremoris, Str. faecalis and lactobacilli. Pyruvate as a sole source of carbon gave a poor yield of A + D compared to itself in the presence of glucose in case of most of the streptococci and all of the lactobacilli.The largest amount of diacetyl was produced by 70% of the streptococci from citrate added to skim milk, and by the great most of the lactobacilli from pyruvate in PYG medium.
Produktion von Acetoin durch Milchsäurebakterien in mit Zitrat und Pyruvat angereicherter Magermilch
Zusammenfassung Insgesamt 32 Säureweckerkulturen der Gattungen Streptococcus, Leuconostoc und Lactobacillus wurden unter Verwendung unterschiedlicher Nährsubstrate auf die Bildung von Acetoin und Diacetyl untersucht. Es zeigte sich, daß je nach Nährbodenzusammensetzung und Bakterienstamm unterschiedliche Mengen der genannten Aromastoffe gebildet wurden.
  相似文献   
992.
993.
Selenium levels in human milk in the winter period ranged from 5.3 μg/l to 23.8 μg/l, the mean value being 11.0 μg/l. The nursing women were divided into several groups according to the results of a questionnaire, i.e. according to their social status (refugees or otherwise), number of deliveries, post partum days, the weight they had gained during pregnancy, their age and smoking habits. The mean levels of selenium for each group are presented. Selenium was determined by hydride generation atomic absorption spectrometry.  相似文献   
994.
Studies on fatty acids composition of hop extract obtained from Vurtenberg hop by extraction with a threecomponent mixture was carried out. It has been established that the content of fatty acids in hop extract is 0.3% ±5%. Fatty acids composition was determined by Gas-chromatographic analysis. The presence of the following unsaturated fatty acids has been proven: C16:1; C18:1; C18:2; C18:3; C20:1 which represent about 40% of the general content of fatty acids in the extract.  相似文献   
995.
基于数字图像的非均质岩土工程材料的数值分析方法   总被引:17,自引:0,他引:17       下载免费PDF全文
提出了一种基于数字图像的非均质岩土工程结构的二维数值分析方法。以花岗岩为例,先将岩石的表面图像导入计算机中;然后采用基于彩色空间的数字图像技术将组成花岗岩的几种主要材料:长石、石英和黑云母一一分辨出来并再现岩石的细观结构;再通过一个简单的线性转换,将图像细观结构转换为矢量细观结构;最后,岩石的矢量细观结构可以与数值计算方法--有限元法或有限差分法结合,从而实现非均质岩石材料的力学分析。采用有限差分法FLAC程序来分析岩石的破坏过程。传统室内试验数值模拟表明材料的细观结构对应力分布和破坏模式有着明显的影响,基于数字图像的数值分析方法可以真实地实现岩土工程材料的非均质分析。  相似文献   
996.
Through a simple application, this research demonstrates the potential and procedure of applying computer vision and control techniques in developing automated real-time statistical process controllers (SPC). A computer vision system was developed to sample and measure quality variables (area, length, and width) of an extruded food product. Shewhart control charts were used to monitor the state of statistical control. Corrective actions were determined by using a PI control algorithm to minimize the product size variation caused by material inconsistency in moisture content. the system was implemented and tested. Considerable improvement was achieved in product size uniformity.  相似文献   
997.
Oxidative rancidity in fresh, frozen and cooked chicken breast and leg meat was evaluated by measuring malondialdehyde (MDA) in fat from meat with an improved 2-thiobarbituric acid (TBA) assay with antioxidant protection, and by measuring the relative fluorescent products of organic and aqueous layers from Folch extracted meat. Fresh samples were frozen for 3 and 6 months at ?18 °C and cooked in convection and microwave ovens. Frozen storage for 3 and 6 months either before cooking or after convection and microwave cooking substantially increased MDA concentrations in fat from meat, whereas cooking was more effective in generating fluorescent products. There were no significant differences in free MDA concentrations or TBA numbers in chicken meat between convection and microwave cooking methods. The certain secondary fluorescent products were significantly higher in meat cooked by convection oven. The initial levels of either MDA or fluorescent products in meat are of primary importance in determining the final MDA and fluorescence levels after processing.  相似文献   
998.
999.
This study determined quality changes of whole ungutted golden gray mullet (Liza aurata) while stored in ice or in a refrigerator (without ice). Changes in microbiological quality (total viable and psychrophilic counts, lactic acid bacteria and Enterobacteriaceae), chemical quality (pH, total volatile basic nitrogen, trimethylamine, peroxide value, thiobarbituric acid, and free fatty acids), and raw fish sensory attributes were evaluated during 16 days of storage. The sensory attributes of golden gray mullet correlated well with the microbiological analyses (r = 0.92). Based on the overall raw acceptability sensory scores and the microbiological tests, the shelf life of the raw golden gray mullet was 10 days in ice and about 14 days in a refrigerator.  相似文献   
1000.
There is a paucity of data in respect of the nutritional quality of complementary foods for infants and young children aged between 6 and 12 months. The primary objective of this study was to examine nutritive values of such complementary infant food on the UK market in order to ascertain their suitability relative to dietary guidelines for the 6–9 months age group. Quantitative analyses were conducted on eight different products representing four popular brands (meat and vegetable based) currently on sale in the UK. Eight major mineral and trace elements, namely: calcium, copper, magnesium, iron, zinc, potassium, sodium and selenium were measured by ICP–OES and ICP–MS. The results of these studies were referenced to the Recommended Nutrient Intake (RNI) values for 6–9 months old children, and a menu of entire daily intake of minerals and trace elements was composed taking into consideration the nutrient and energy intake from milk consumption. Based on these comparisons, all the food samples studied in this work contained less essential minerals than expected from the RNI values except for potassium in meat and vegetable based recipes. These results suggest that commercial complementary infant foods on the UK market may not contain the minimum levels of minerals required for the labelling declaration of micronutrient content (Commission Directive 2006/125/EC). This provides opportunities and scope for product optimisation to improve their nutritive value.  相似文献   
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