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亚麻脱胶过程中常用酶类的动态变化   总被引:10,自引:0,他引:10       下载免费PDF全文
 对亚麻快速生物脱胶和温水沤麻过程中的果胶酶、木聚糖酶、纤维素酶、微生物、pH值和还原糖等进行了动态变化研究。结果表明,2种脱胶过程中果胶酶和木聚糖酶的变化趋势基本相似,酶活性脱胶前期均增加缓慢,中后期迅速增加;纤维素酶活性的变化趋势有明显的区别,快速生物脱胶的纤维素酶酶活性增加幅度小,酶活性低(0.05 IU/mL左右),温水沤麻的纤维素酶在发酵72 h后迅速增加,脱胶完成后酶活性达0.337 9 IU/mL;微生物的变化趋势基本相似,在脱胶前期迅速增加、脱胶完成时开始下降;pH值和还原糖量的变化趋势分别呈“U”型和“M”型。  相似文献
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The variation in myofibrillar protein thermostability was compared for various fish species, using differential scanning calorimetry. The tropical fish, catfish ( Clarius gariepinus ), carp ( Cyprinus carpio ), Nile perch ( Lates niloticus ), red snapper ( Lutianus sebae ), red mullet ( Parpeneus barberinus ), sea bream ( Gymnocranius rivalatus ), and cold-water reared trout ( Salmo gairdneri ) and cod ( Gadus morhua ) were analysed. Onset temperature of myofibrillar protein denaturation occurred at up to 11°C higher for tropical species (43.5°C, catfish), than cod (32.6°C) at pH 7 and low ionic strength (I). As pH (6.0-8.0) and I (0.05-1.00) were increased, thermal denaturation temperatures of myosins from tropical, but not cold-water, species decreased. Enthalpies of myofibrillar denaturation decreased for all species with increasing pH and I. Only one thermal transition was detected for myosin at pH 6 and low I, increasing to three as pH and I were increased. Changes in thermal characteristics of myosin subunits over iced and frozen storage suggest more rapid deterioration in cold-water than in tropical fish. The differences in myofibrillar stability of fish from different habitat temperatures have implications for the processing and storage of tropical fish.  相似文献
3.
Hyun Jung  Kim  Hao  Feng  Stoyan A.  Toshkov  Xuetong  Fan 《Journal of food science》2005,70(3):M179-M185
ABSTRACT: The effect of warm water dip in combination with irradiation on quality of fresh-cut green onions was studied. Fresh-cut green onions were treated with and without warm water (50°C for 20 s) and packaged prior to irradiation at 0, 0.5, 1.0, and 1.5 kGy, then stored at 4°C for 14 d. Color, texture, decay percentage, electrolyte leakage, sensory qualities, and total aerobic count (TAC) were measured at 1,4,8, and 14 d of storage. The warm water treatment reduced the TAC by 0.9 log initially but the beneficial effect disappeared during storage. With the test conditions used in this study, the warm water treatment did not provide added benefits for quality improvements. Irradiation at all tested doses reduced TAC and the development of decay and off-odor, improved visual quality, and preserved green color.  相似文献
4.
The optimal conditions of washing iceberg lettuce with acidified warm water to improve the hygienic and sensory product quality were determined with the aid of a central composite design. To determine the criteria of product quality, in the course of storage for 13 days at 4 °C lettuce was subjected every 2 days to sensory evaluation. The sensory values were found to correlate with the physical measurements of color (a* value) (R2=0.83) and texture (specific energy of deformation) (R2=0.77), respectively. Color, texture and overall visual quality correlated with product acceptability (R2=0.96, 0.97, 0.96, respectively). In the experiments of series I, the effect of temperature at washing (45–50 °C), pH (4–5) and treatment time (5–10 min) were investigated and the results were used for the construction of a model to describe the effects on color and texture and to define an area of sensory product acceptance. In series II the parameters were changed to ranges of temperature (45–50 °C), pH (4.6–6) and treatment time (2–5 min), and the effect on the reduction of bacterial counts within the area of product acceptance was defined. In that area reduction rates of total counts by 0.9–2.9 log cfu/g and Enterobacteriaceae by 0.8–3.0 log cfu/g were achieved. The initial germ- reducing effect was sustained until the end of storage for 7 days at 4 °C. At 50 °C, washing for 5 min at pH 4.93, the total bacteria and Enterobacteriaceae were reduced by 2.9 and 3.7 log cfu/g, respectively. The removal of the two groups of bacteria exhibited characteristic differences. Two independent experiments confirmed the reliability of the models.  相似文献
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A nanoclay composite film was produced using warm water fish gelatin as a base material and its physical, mechanical, and molecular weight change properties were observed after treatment with microbial transglutaminase. The viscosity of the MTGase-treated gelatin solution (2% w/w) increased from 86.25 ± 1.77 (0 min) to 243 ± 12.37 cp (80 min). SDS–PAGE results indicated that the molecular weight of fish gelatin solutions increased after treatment with microbial transglutaminase. Tensile strength decreased from 61.60 ± 1.77 (0 min) to 56.42 ± 2.40 MPa (30 min), while E% increased from 13.94 ± 5.09 (0 min) to 15.78 ± 5.97% (30 min) at 2% (w/w) MTGase concentration. The oxygen permeability and water vapour permeability did not change as a function of treatment time at 2% (w/w) MTGase concentration. The incorporation of nanoclay inhibited the increase of oxygen permeability. Film colour values (L, a, and b) did not change, but haze values increased from 5.24 ± 0.40 (0 min) to 6.44 ± 0.94 (50 min). XRD and TEM results suggested that the nanoclay was exfoliated in fish gelatin film.  相似文献
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