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In recent years, microwave heating has become a common method for pasteurization and sterilization of food. Honey is a sweet substance produced by worker honeybees from nectar of flowers. The major microbial contaminants include moulds and yeasts, as well as the spore-forming bacteria, being their counts indicative of honeys' commercial quality and safety. Paenibacillus larvae is also of interest since it causes American foulbrood (AFB) in honeybee larvae. The main quality factors that are used in the honey international trade are moisture, hydroxymethylfurfural content (HMF), and enzymatic indices. Moreover, honey exhibits several thermal events, the most important being the glass transition temperature (Tg). The aim of this work was to evaluate microwave effect (800 watts during 45 and 90 seconds) on microbial content in particular over P larvae spores retained in honey, and on physicochemical and thermal properties. Microwave promoted a decrease of microbial count with time of exposure, including P larvae. Moisture content diminished after treatment, while Tg increased linearly, and acidity decremented in the majority of cases. Honeys darkened and HMF exceeded the permissible value. Diastase and glucose-oxidase enzymes were totally inactivated by microwave treatment.
Structures and properties of starches isolated from Japanese rice and different botanical sources were investigated. Amylopectin unit chain-length distributions were analyzed using HPLC and HPAEC-PAD for comparing the distributions of unit chains of isoamylase-debranched amylopectins. Thermal properties were measured by DSC. It was found that there were at least five groups of Japanese rice amylopectins having different unit-chain distributions. The four kinds of starches (Akenohoshi, Haiminori, Tashukei 431, and Kenkei 2064) had the amylopectins of long chain-length compared with the other rice starches. It was observed that the gelatinization temperature of their four native starches were higher and the enthalpy change (•H) of gelatinization of their four retrograded starches showed larger than the other rice starches. In the starches of different botanical sources, the ratios of unit chains of DP6-12 (Fr.A) of amylopectins of quinoa, barley, buckwheat, Japanese radish, and tulip were higher, and the gelatinization temperatures were lower than the values of other starches. The ratios of Fr.A of amylomaize V and VII were lower, and the gelatinization temperatures were higher than the respective values of other starches. There were highly negative relationships between the ratio of short unit chain-length in amylopectin and gelatinization temperature.
TSK gel permeation chromatography of non-granular starches, amylopectin chain-length distributions measured by HPAEC-PAD, and DSC characteristics of starches of maize endosperms possessing different alleles at the amylose-extender (ae) loci were studied. GPC of non-granular starches through Toyopearl columns showed that elution profiles for 5 ae mutants, Oh43 inbred line ae (standard ae), ae- RWB-2 and ae-RWB-3, and W23xL317 hybrid line ae-PP and ae-Bol 561, were similar to a commercial ae starch, Hylon VII and different from Hylon ae starch and normal maize starches. The elution profile for W23xL317 ae-emll was similar to Hylon and different from Hylon and normal maize starches. HPAEC-PAD of isoamylase-debranched starches showed that the 5 ae mutants were uniquely ae type similar to Hylon VII and different from Hylon V. W23xL137 ae-emll had the amylopectin chain-length distribution similar to Hylon . Gelatinization temperatures (Tp) of the ae starches measured by a Setaram Micro DSC III were high compared with the normal counterpart starches except for Oh43 ae-RWB-1 starch. Oh43 ae-RWB-1 starch had structure and thermal characteristics similar to the normal maize starch.
The method of Differential Scanning Calorimetry (DSC) was used for determination of the garlic specific heat. The measurements were carried out in the range of material moisture from 17 to 87% and in the temperatures from 283 to 333 K (10-60°C). The analysis of measurement results, aided with the methods of mathematical statistics, summarises the complex behaviour of the change in specific heat versus moistening of garlic and its temperature, and compares it with reference data.
Buffalo’s milk protein products, total milk proteinate (TMP), rennet casein, and lactic acid casein were studied. The chemical composition was determined and some properties (water and oil absorption capacity, emulsion activity, foam expansion, and buffer capacity) of these products were also determined. The results indicated some differences in the chemical composition and electrophoresis bands of protein between total milk proteinate, rennet casein and lactic acid casein. The TMP was characterised by the lowest ash and moisture contents with highest protein contents compared to the other protein products. There is no remarkable effect of drying methods on the chemical composition within each type of protein products. Total milk proteinate contains some whey proteins which are high in alanine, cystine when compared with rennet casein. Lactic acid casein had high contents of amino acid proline. On the other hand, the rennet casein had a low content of sulfur containing amino acids cysteine and methionine. Differences between total essential amino acid (TEAA) of total milk proteinate and lactic acid casein were significantly (p<0.05) higher than those of rennet casein. Freeze dried total milk proteinate exhibited excellent foaming and emulsifying potential when compared with oven-dried caseinate. For all protein types, the maximum WAC can be seen for freeze-dried milk proteinates, whereas the minimum value was for oven dried rennet casein. The minimum value of emulsion capacity and surface tension was obtained at pH 4.5 and 2.5 in all types of proteinates, whereas the maximum values were found at pH 10.5. Relative viscosity of TMP solutions was higher than those of rennet and lactic acid casein. However, relative viscosity values tended to decrease with lowering or increasing the pH values of the solutions from the neutral pH value. Calorimetric analysis showed two major enthalpy changes in the tested caseinate samples. The first change occurred at peak temperature range of 92.2°C to 100.8°C for the moisture removal, while the second change occurred between 273.9°C and 314.6°C for protein degradation. The enthalpy values ranged between 218.3 to 268.4 J/g for moisture removal. Total milk proteinate showed two major peaks for protein degradation indicating the presence of whey proteins and milk caseins.
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