Effect of corn particle size on site and extent of starch digestion in lactating dairy cows

Two experiments were conducted to determine the effects of corn particle size (CPS) on site and extent of starch digestion in lactating dairy cows. Animals were fitted with ruminal, duodenal, and ileal cannulas. Dry corn grain accounted for 36% of dry matter intake. In experiment 1, 6 cows were used in a duplicate 3 x 3 Latin square design. Semiflint corn was used. Corn processing methods were grinding, medium rolling, and coarse rolling. The mean particle size of the processed corn was 730, 1807, and 3668 microm, respectively. Rumen digestibility of starch linearly decreased from 59% with ground corn to 36% with coarsely rolled corn. Similarly, small intestine digestibility linearly decreased with increased CPS, and consequently, the amount of starch digested in the small intestine was not affected by corn processing. In experiment 2, 4 cows were used in a 2 x 2 crossover design. Dent corn was used. Corn processing methods were grinding and coarse rolling. The mean particle size of the processed corn was 568 and 3458 microm, respectively. Rumen digestibility of starch decreased from 70% with ground corn to 54% with coarsely rolled corn. Small intestine digestibility of starch was not significantly affected by CPS, and the amount of starch digested in the small intestine tended to be greater for rolled than for ground corn. In both experiments, starch total tract digestibility decreased with increased CPS. In conclusion, CPS is an efficient tool to manipulate rumen degradability of cornstarch. In midlactation cows, the decrease in the amount of starch digested in the rumen between grinding and coarse rolling is partly compensated for by an increase in the amount of starch digested in the small intestine with dent genotype, but with semiflint genotype postruminal digestion is not increased and rumen escape starch is not utilized by the animal.     

Use of exogenous fibrolytic enzymes to enhance in vitro fermentation of alfalfa hay and corn silage

Two in vitro experiments were performed to identify promising exogenous fibrolytic enzyme products (EFE) and optimum dose rates (DR) for improving the degradation of alfalfa hay and corn silage. The relationship between enzymatic activity and fermentation responses was examined to identify optimum formulations. In experiment 1, 5 EFE containing mainly endoglucanase and xylanase activities, with different ratios between the 2 activities, were assessed at a DR of 0.7, 1.4, and 2.1 mg/g of DM forage. Milled alfalfa hay or corn silage was incubated in an in vitro batch culture with buffer, ruminal fluid, and EFE. Gas production (GP) was measured during 24 h of incubation, and degradabilities of DM and fiber were measured after terminating the incubation at 24 h. Two (E1 and E3) EFE substantially improved GP and degradation of alfalfa hay and corn silage fiber. The optimum DR of these EFE was 1.4 mg/g of DM for both forages with improvements in NDF degradability up to 20.6% for alfalfa hay and up to 60.3% for corn silage. Whereas added activities of endoglucanase and exoglucanase were positively correlated with improvement in NDF degradability for alfalfa hay and corn silage, there was no relationship between added xylanase activity and NDF degradability. The 2 most promising EFE from experiment 1 were reevaluated in experiment 2, alone and in combination with a high xylanase EFE, to determine whether their effectiveness could be enhanced by decreasing the endoglucanase to xylanase ratio. The 2 EFE improved GP and fiber degradation in a manner similar to that observed in experiment 1, but the combination treatments resulted in no further beneficial effects. Exogenous fibrolytic enzyme products can greatly improve forage utilization, but DR and the activities supplied are critical for achieving this response. Products used with alfalfa hay and corn silage should contain high endoglucanase activity, with an ideal ratio of endoglucanse to xylanase.     

玉米胚芽蛋白及其在食品工业中的应用

概述玉米胚芽蛋白的营养价值和功能性质,并介绍玉米胚芽蛋白在焙烤食品、肉制品、饮料等方面的应用。     

淀粉-MMA接枝共聚物的半干法合成新工艺

以硝酸铈铵(CAN)为引发剂,采用固相半干法合成了玉米淀粉(CS)接枝甲基丙烯酸甲酯(MMA)共聚物。考察了含水量、反应体系的酸性、反应时间与温度、MMA单体和引发剂CAN用量等因素对接枝共聚反应的影响。结果表明,体系含水质量分数为35%左右,CAN用量为CS质量的1.5%～3%,反应温度在40～50℃,反应时间为0.5h左右,可得到接枝率、接枝效率和单体转化率均较高的接枝共聚物。     

戊二酸蜡质玉米淀粉酯的制备及理化性质研究

以原蜡质玉米淀粉为原料,戊二酸酐为酯化剂,乙醇为反应溶剂制备戊二酸淀粉酯(EGAS)。采用傅里叶变换红外光谱（FT-IR）、扫描电子显微镜（SEM）、X射线衍射仪（XRD）及布拉班德粘度仪等对样品进行表征及理化性能分析。结果表明：FT-IR显示戊二酸淀粉酯在1730 cm-1处和1565 cm-1处出现了新的吸收峰,其中1730 cm-1处为C=O的伸缩振动吸收峰,1565 cm-1处为游离的-COO-的反对称伸缩振动吸收峰,表明了淀粉分子中成功接入了戊二酸基团;改性前后淀粉的表观形貌变化,证实了反应不仅发生在淀粉颗粒表面,也发生在淀粉颗粒内部;XRD分析显示改性后的淀粉仍属于A型结晶结构,表明了反应主要发生在无定形区;布拉班德粘度分析则表明了改性后的淀粉（DS=0.0450）峰值粘度提高了2.33倍;EGAS的冻融稳定性和抗剪切力均强于原淀粉,糊的透明度得到改善。     

玉米油精炼过程氯离子含量变化及其对3-氯丙醇酯和缩水甘油酯含量的影响

对取自安徽、河北、山东等地玉米油加工厂的玉米油毛油、待脱臭油和成品油中的氯离子、3-氯丙醇（3-monochloro-1,2-propanediol,3-MCPD）酯和缩水甘油酯（glycidyl esters,GEs）含量进行检测,并在实验室明确可控的条件下对玉米毛油进行精炼,检测精炼过程氯离子、3-MCPD酯和GEs含量,与玉米油加工厂实际精炼过程的含量变化情况进行对比分析,研究玉米油精炼过程中氯离子含量变化及其对3-MCPD酯和GEs含量变化的影响。结果表明：所检测的所有玉米油样品中均含有氯离子、3-MCPD酯和GEs,其中毛油中氯离子含量最高,为0.628～2.029 mg/kg,毛油中3-MCPD酯和GEs含量分别为0.547～1.083 mg/kg和0.246～0.721 mg/kg;待脱臭玉米油中氯离子含量为0.110～0.374 mg/kg,较毛油中含量明显降低,3-MCPD酯和GEs含量分别为0.933～1.422 mg/kg和0.246～0.432 mg/kg,3-MCPD酯较毛油中含量有所升高,GEs含量变化不明显。脱臭油中3-MCPD酯和GEs含量分别为3.523～4.541 mg/kg和1.501～13.584 mg/kg,较待脱臭油中含量大幅升高,其中一个油样中含量分别增加3.5 倍和32.1 倍,同时该油样中氯离子含量的降幅也最大（0.287 mg/kg）。对实验室精炼过程及工厂精炼过程的玉米油样品检测分析显示,无论是实验室精炼还是工厂实际生产,氯离子含量均随精炼过程逐渐减少,其中降幅最大的是水化脱胶和碱炼脱酸工序（降幅为76.1%～81.3%）;3-MCPD酯和GEs在水化脱胶、碱炼脱酸及吸附脱色过程的含量变化不大,经脱臭后含量大幅升高,同时伴随脱臭过程氯离子含量的降低,并且氯离子含量降幅越大3-MCPD酯的升幅越高。研究结果明确了玉米油精炼过程氯离子和3-MCPD酯及GEs含量的变化规律,以及待脱臭玉米油中氯离子含量对脱臭油脂中3-MCPD酯和GEs含量的影响,对玉米油精炼乃至其他植物油生产中3-MCPD酯和GEs的风险防范和控制都具有指导意义。     

利用一株凝结芽孢杆菌发酵酸解玉米秸秆生产乳酸

该研究拟考察凝结芽孢杆菌（Bacillus coagulans）利用玉米秸秆生物炼制乳酸的效果。以凝结芽孢杆菌CGMCC No.7635为菌种,利用2%硫酸预处理后的玉米秸秆为碳源、20 g/L酵母粉为氮源,添加20 FPU/g纤维素酶后开展糖化发酵生产乳酸实验。结果表明,发酵65 h后可获得乳酸含量为（38.38±1.03） g/L,其中L-乳酸光学纯度为（99.23±0.22）%。进一步使用补料发酵工艺,添加经预处理的玉米秸秆,可最终获得乳酸含量为（82.56±1.28） g/L。建立的玉米秸秆生物炼制乳酸工艺操作简单、产物浓度高,具有工业应用潜力。     

玉米薄饼贮藏品质分析及货架期预测模型建立

为探索玉米薄饼贮藏品质变化规律,以玉米粉和小麦粉为原料制备韧性玉米薄饼,研究玉米薄饼贮藏14 d内感官品质、理化指标、微生物指标、质构及老化特性的变化,探讨影响玉米薄饼贮藏品质变化的主要因素,建立玉米薄饼货架期预测模型。结果表明：贮藏在4、25 ℃和40 ℃ 3 种温度条件下,玉米薄饼的酸值、过氧化值、菌落总数、热焓值、b*值随贮藏时间的延长逐渐增大;韧性、延展性、L*值、a*值、感官评分逐渐降低。通过相关性分析得出菌落总数可以作为反映玉米薄饼贮藏货架期的品质因子,建立不同温度条件下菌落总数生长动力学模型及随贮藏温度变化的动力学模型,其准确因子为1.126～1.281,偏差因子为0.899～1.051。在此基础上建立韧性玉米薄饼货架期预测模型,预测值和实际值的相对误差为－4.10%～2.91%,模型能够快速可靠地预测饼的货架期,可为玉米饼及相关制品的工业化生产提供技术和理论依据。     

热风微波干燥龙眼肉工艺的优化

针对龙眼肉原料受热不均匀和微波干燥速率过快与局部过焦的问题,尝试在干燥前将原料均匀涂抹经过适度加热的玉米调和油,然后再进行热风微波干燥,旨在通过降低微波干燥的加热速度来提高龙眼肉的生产效率和产品品质。文中建立了具体的感官评价体系,从功率密度、加热方式、初始含水率3个方面分析添加油脂膜的龙眼肉在微波干燥过程中的颜色变化、干燥速率变化、感官评价变化。实验找到了经油脂涂膜处理的龙眼肉在热风微波干燥工艺的优化点:4W/g功率、微波10s间歇40s、初水分含量50%～60%、食用油脂含2%～4%。与未使用任何预处理的热风微波干燥龙眼肉相比较,该工艺可以得到更加良好的品质,且保质期在6m。     

Heat-moisture treatment of high-amylose corn starch increases dietary fiber content and lowers plasma cholesterol in ovariectomized rats

ABSTRACT:  The effect of dietary high-amylose corn starch (HACS) of varying dietary fiber (DF) content on plasma cholesterol was examined in ovariectomized (OVX) rats. Gelatinized normal corn starch (G-CS) was used as a reference. OVX rats were fed a fiber-free purified diet containing G-CS, HACS, gelatinized high-amylose corn starch (G-HACS), or heat-moisture treated HACS (HM-HACS) at 400 g starch/kg diet for 21 d. The DF content of G-CS, HACS, G-HACS, and HM-HACS measured by the AOAC method was 0.1, 19.3, 2.4, and 64.5 g/100 g, respectively. The dry weight of cecal contents, cecal wall weight, the amount of short chain fatty acids in cecal contents, the amount of bile acids in small intestinal contents, and fecal excretion of neutral sterols increased logarithmically with increasing DF, while total plasma cholesterol concentration decreased. On the other hand, hepatic CYP7A1 activity, fecal dry weight, and fecal excretion of bile acids increased linearly with increasing DF, while body weight gain decreased. The hypocholesterolemic effect of HACS in OVX-rats appeared to be more effective by heat-moisture treatment.