添加大米粉对面包面团揉混特性和拉伸特性的影响

以高筋面粉为对照,研究添加不同比例的大米粉所形成的混粉面团揉混特性和拉伸特性的影响。结果表明,随着大米粉添加量增加,混粉面团的形成时间、稳定时间和粉质指数呈下降趋势,当大米粉添加量超过20%时,对粉质指标产生显著性影响;当大米粉的添加量为20%,醒发时间为45 min和90 min的延伸度、拉伸面积呈极显著降低。醒发的时间越长,面粉的拉伸特性变化越小。因此,大米粉添加量为20%以内时,对面团揉和性能和拉伸性能影响较小。     

现代工具在“食品冷冻冷藏技术”教学中的应用

立足新时代,努力培养新工科人才的时代号角要求高校以人才输出、成果培育为导向,加强课程的工程性、应用性教学。以"食品冷冻冷藏技术"教学为例,在传统教学的基础上,引入现代工程软件"立体化教学",通过采用现代工具对食品冷却过程进行能耗和温度等参数的预测和模拟,激发学生的学习兴趣,培养学生采用现代工具解决复杂工程问题的能力和自主创新精神。     

新疆冰川冰缘冻土低温淀粉酶部菌株分子生物学鉴定及酶学特性研究

[目的]对新疆冰川冰缘地区冻土中筛选出的具有良好产低温淀粉酶能力的菌株进行分子生物学鉴定,分析其酶学特性.[方法]用种子培养液活化菌株提取基因组DNA进行PCR扩增,将扩增成功菌株的PCR产物测序结果通过NCBI数据库比对,对冻土中产低温淀粉酶菌株的16S rDNA序列用MegAlign Fasta软件进行系统发育分析.利用Yoo改良法测低温淀粉酶酶活力.[结果]菌株A-2,A-3,A-4经16S rDNA序列分析获得的序列与数据库中解淀粉芽孢杆菌(Bacillus amyloliquefaciens strain NBRC 15535 16S ribosomal RNA,partial sequence(NR_04145))比对相似率达到99;.该菌株产生的低温淀粉酶的最适作用温度为30℃,最适pH为6.[结论]菌株A-2,A-3,A-4均属解淀粉芽孢杆菌.     

晚播对小麦籽粒谷蛋白及GMP积累动态的影响

选用高分子量谷蛋白亚基(HMW-GS)在Glu-B1位点等位变异的4个近等基因系材料,研究了在正常播期和晚播条件下小麦籽粒谷蛋白和谷蛋白大聚体(GMP)的积累动态及面团稳定时间。结果表明:在遗传背景相同的条件下,各材料籽粒谷蛋白在正常播期和晚播中积累动态均是从低到高,花后30～35d为快速积累期,含优质高分子量谷蛋白亚基材料在此时期积累较快。GMP在花后12d左右已大量积累,随着灌浆进程的推进快速下降,灌浆中期降到最低点,不同亚基材料降到最低点的早晚不同,亚基17+18出现最低点早,上升时的积累量较其他亚基大;在正常播期中上升直到成熟,在晚播中灌浆后期又有下降的趋势。晚播对Glu-B1位点等位变异的4个材料谷蛋白及GMP含量和面团稳定时间都有较大的影响,但影响的程度不同,17+18最大,7+9次之,7+8最小。推测不同亚基材料谷蛋白及GMP积累动态的差异是导致其品质形成及稳定性的关键。     

Effect of quick-freezing temperature on starch retrogradation and ice crystals properties of steamed oat roll

Oat roll is one of the traditional oat wholemeal foods. The purpose of this work was to investigate the effects of quick freezing at −20 °C, −40 °C and −80 °C for 90 min before frozen storage on the quality of frozen steamed oat roll. Quick freezing at −40 °C and −80 °C inhibited the increase of peak gelatinization temperature, enthalpy and the ordered degree of oat roll starch, therefore postponing starch retrogradation. The cross-section microstructure confirmed that reducing the quick-freezing temperature could prevent the increase of ice crystals size, ruptured structures and maintain the integrity of internal structure. As the storage time extend, the ice recrystallization led to an increase in size of ice crystals, while a decrease in their number. Frozen steamed oat roll starch had the highest swelling power at the quick-freezing temperature of −80 °C, that indicated strongest water absorption and binding ability when gelatinized again. Texture analysis demonstrated that hardness increased during frozen storage, quick freezing at −80 °C had the best texture properties. Therefore, declining the quick-freezing temperature could obtain a higher quality of frozen steamed oat roll, by means of delaying the starch retrogradation and minimising the size of ice crystals.     

影响面团拉伸仪性能因素的分析

根据国家标准对面团拉伸仪的要求、拉伸仪的原理和结构,分析了影响拉伸仪性能的因素,并指出了提高测试性能的方法。     

Xylanases from microbial origin induce syrup formation in dough

Syrup formation in refrigerated doughs is a problem since it reduces the doughs’ shelf life. Microbial exogenous xylanases associated with wheat kernels were found to play a role in this syruping phenomenon. Using xylanase-producing microorganisms isolated from wheat kernels, we investigated their potency to induce syruping in dough. Growth of the fungal xylanase producer Fusarium sp. (10² colony forming units (CFU)/g dough) and the bacterial xylanase producer Paenibacillus sp. (10⁴ CFU/g dough) in synthetic media and their respective addition to wheat dough could not bring about a significant amount of syruping. However, when these species were grown on moist wheat kernels and an extract of these kernels containing both the organisms and its xylanases was made and added to dough, intensive syruping was noted. This effect was primarily attributed to the xylanases present in the extract. These findings suggest that the involvement of xylanase-producing microorganisms in the syruping phenomenon is situated prior to harvest. Additional quantitative analyses of microbial biomass present on wheat kernels revealed that the fungi in particular could be correlated to higher microbial exogenous xylanase activities on wheat. Our results indicate that the syruping is linked to fungal xylanase production on the wheat kernels in the field.     

Quality attributes of fermented yam flour supplemented with processed soy flour

Pretreated soy flour was used to replace 10, 20, 30 and 40% of fermented yam flour as a protein supplement. The effect of the supplementation on the physicochemical and sensory properties of amala, a popular West African food made from rehydrated yam flour, was investigated. Blanching (10 min in boiling water) and subsequent fermentation (24 h) as pretreatment methods produced flour that was lighter in color than the unfermented samples. Protein content of the yam-soy mixture increased from 3.5% in the control to 19.7% for 40% soy fortification. Water binding capacity increased from 212.6 g/100 g for the yam flour control to 257.3 g/100 g for the blend with 40% soy flour. However, swelling capacity and solubility were adversely affected with increased soy flour addition as dough became sticky and soft. There was no significant difference in color, taste, flavor or overall acceptability when compared with the control up to 20% soy substitution. Dough with 20% soy flour is a possibility for increasing the protein content of yam flour in human feeding.     

Motility and Fertility Evaluation of Thawed Frozen Stallion Semen After 24 Hours of Cooled Storage

Breeding mares with cryopreserved semen requires specialized equipment for storage and thawing and more intensive mare management. The objectives of this study were (1) evaluate the longevity of frozen stallion semen once it had been thawed, extended, and maintained at 5°C for 48 hours in a passive cooling container, and (2) determine fertility potential of frozen semen that had been thawed, extended, and used to inseminate mares after 24 hours of cooled storage. Eight ejaculates were collected and aliquots were cooled in either INRA96 and CryoMax LE minus cryoprotectant at a concentration of 50 million total sperm/mL. The remainder of the ejaculate was frozen in CryoMax LE extender at a concentration of 200 million total sperm/mL. Semen was thawed using 1 of 3 thawing protocols, and diluted to a concentration of 50 million total sperm/mL in either INRA96 or CryoMax LE minus cryoprotectant and cooled to 5°C. Sperm motility was evaluated at 24 and 48 hours. Eight mares were inseminated over two estrous cycles using frozen semen that had been thawed, extended in INRA96, and cooled for 24 hours. There was no difference in progressive motility at 24 or 48 hours of cooled-storage post-thaw between the 3 thawing protocols. An overall per cycle pregnancy rate of 56% (9/16 cycles) was achieved using frozen-thawed semen that had been extended and cooled for 24 hours. In summary, frozen stallion sperm was thawed, extended, and cooled to 5°C for 24 hours and still maintained adequate (>30%) sperm motility and fertility.     

Influence of Wheat Protein Contents and Fractions on Dough Rheological Properties as Determined by Using a Reconstitution Method

A strong gluten wheat cultivar Shannong 12 and a medium-strength wheat cultivar Shannong 11 were used to investigate the effects of wheat protein contents and protein fractions on dough rheological properties using a reconstitution method. The results indicated that the peak height, peak width, peak integral, resistance to extension and area under the curve were increased when protein content increased to 120, 140, and 160% （w/w） of the protein content in the base flours for doughs made from each wheat cultivar. All protein fractions were added to each of the base flours at three levels （0.25, 0.50 and 1.00%, w/w） based upon the protein content. The mixograph dough development time, peak width, and resistance to extension increased when the glutenin, insoluble glutenin, soluble glutenin, and glutenin macropolymer were added and increased systematically with increasing levels of these fractions. Peak integral increased by adding and increasing protein content, however, albumin-globulin had no obvious effects. Extensibility at rupture decreased when the glutenin, insoluble glutenin, soluble glutenin, and glutenin macropolymer were added, and decreased systematically with increasing levels of these fractions. However, extensibility at rupture increased when the monomeric protein, albumin-globulin, and gliadin were added, and increased systematically with increasing levels of these fractions.