高浓度木薯粉浆糊化液化粘度的研究

为了更好地利用高浓度木薯醪液进行酒精发酵,应用旋转粘度计对高浓度木薯粉浆的糊化液化粘度进行研究。实验结果表明:木薯粉浆的糊化曲线符合典型的淀粉糊化曲线;其糊化液化粘度随着粉浆浓度的增加而上升;在淀粉含量相同的条件下,木薯淀粉浆比木薯粉浆起糊快且峰值粘度较高;糊化前加入液化酶可以大幅度降低峰值粘度,加入10u/g木薯粉耐高温α-淀粉酶,10%（vol）酒精度对应木薯粉浆的液化峰值粘度仅为不加酶时的3·26%,15%（vol）酒精度对应物料的液化峰值粘度仅为10%（vol）酒精度对应物料在不加酶时的6·52%。      

阿魏酸对小麦淀粉理化特性的影响

以小麦淀粉为原料,分别通过扫描电镜分析、傅里叶红外图谱分析、X-衍射图谱分析、差示扫描量热仪分析及快速黏度测试仪(RVA)分析,研究了添加0、5%、10%、15%、20%(w/w淀粉干基)阿魏酸后小麦淀粉的微观形貌、结晶性质、热力学特性及糊化特性。结果表明:随着阿魏酸含量的增加,淀粉表面不规程度增加,致密性降低;阿魏酸添加量至10%时,T₀(糊化初始温度)、T_P(糊化峰值温度)、T_C(糊化最终温度)和ΔH(糊化焓值)发生显著降低(p<0.05),说明阿魏酸的添加降低了小麦淀粉的稳定性;红外光谱表明,添加阿魏酸后,小麦淀粉在(1045/1022) cm^-1峰强度比值减小,说明添加阿魏酸后小麦淀粉有序性降低;X-衍射图谱表明,糊化后小麦淀粉由原来的A型变为B+V型,并表现出酸的衍射峰明显,说明阿魏酸与小麦淀粉未形成包合物。RVA分析表明,添加阿魏酸降低了小麦淀粉的峰值粘度、保持粘度、最终粘度和回升值降低,而崩解值增大,说明阿魏酸抑制了小麦淀粉的老化进程,扫描电镜分析也证明了阿魏酸抑制了淀粉的老化过程。     

RVA分析碳酸钠对玉米淀粉和马铃薯淀粉糊化性质的影响

主要研究了碳酸钠(Na2CO3)对玉米淀粉和马铃薯淀粉糊化性质的影响。用粘度速测仪(RVA)分析在浓度为3%、6%的玉米淀粉(MS)和马铃薯淀粉(PS)中加入不同量的碳酸钠(0、0.02、0.04、0.06、0.08g)后的糊化参数。当将0.02、0.04gNa2CO3加入到浓度为6%MS中时,未测得第二个峰值粘度,而加入0.06、0.08g时,第二个峰值粘度出现,且发现加入Na2CO3对玉米淀粉和马铃薯淀粉糊化性质影响不同。用RVA分析3%、6%PS淀粉乳时,加入0.02gNa2CO3后,除糊化温度和回值外,其它RVA谱特征值显著降低,但进一步增加Na2CO3的量,谱特征值没有明显地变化。而对6%MS而言,由于Na2CO3的加入,使得峰值粘度、崩解值、回值增加而糊化温度降低。      

大米谷蛋白对大米淀粉理化特性的影响

本文研究了低变性大米谷蛋白的添加对大米淀粉的持水、糊化、流变与质构特性的影响。结果表明,大米谷蛋白的添加(0~20%)会逐渐降低大米淀粉的持水能力,延迟其水化过程。淀粉的黏度特性曲线、糊化晗值、峰值黏度、崩解值和回生值随谷蛋白添加量的增加而逐渐降低,但起始糊化温度和峰值温度无明显变化。流变数据证实,蛋白添加量为0~10%时,淀粉-蛋白复合物的剪切应力和表观粘度随添加量增加而增加,当谷蛋白添加量为20%时,复合物的剪切应力和表观粘度迅速减小,大米淀粉的糊化特性和凝胶特性发生明显弱化。     

氢氧化钙对玉米粉糊化的影响

通过对添加氢氧化钙的玉米粉热处理后其膨胀力、持水性及糊化程度的分析表明,在氢氧化钙浓度范围0%~1%(w/v)内,低浓度的Ca(OH)_2可提高淀粉颗粒的膨胀力和持水性,氢氧化钙浓度大约在0.4%(w/v)时淀粉的膨胀力、持水性和糊化峰值黏度表现为最大,之后随着浓度的增加而减小。通过差示扫描量热仪和高温偏光显微镜显示,玉米粉糊化温度随着Ca(OH)_2浓度的增加先降低后升高。p H较高时能使淀粉羟基电离,并与Ca~(2+)或[CaOH~+]的结合位点结合使Ca(OH)_2与淀粉产生交互作用。     

小米粉RVA糊化特性的研究

采用快速粘度分析仪（Rapid Viscosity Analyser,RVA）测定了在不同浓度、pH及添加蔗糖、食盐、明矾、硬脂酸等条件下小米糊RVA粘度曲线的变化情况,研究了小米淀粉粘度性质及其影响因素。结果显示,浓度对小米糊粘度性质影响显著,随浓度的增高,糊化温度降低,粘度曲线中峰值粘度及最终粘度升高;pH值对小米糊粘度性质影响较大,过高或过低的pH都会导致峰值粘度降低;随蔗糖添加量的增加,糊化温度略有增高;随着氯化钠浓度的增加糊化温度升高,氯化钠可提高小米糊粘度;明矾对小米糊的峰值粘度影响较大,而对糊化温度影响不大;添加硬脂酸的小米糊的最终粘度显著提高,而峰值粘度变化较小。通过研究为进一步了解小米淀粉的粘度特性及产品开发提供理论依据。     

常用淀粉对甘薯粉糊化特性的影响

利用Brabender粘度仪考察了几种常用淀粉对甘薯粉糊化特性的影响，认为马铃薯、甘薯淀粉使甘薯粉糊化温度降低，玉米、木薯淀粉则使其升高；甘薯、玉米淀粉使甘薯粉糊化时间延长。添加各种淀粉均可使甘薯粉的峰谷粘度提高；马铃薯、玉米淀粉还可大幅度提高其峰值粘度。但马铃薯淀粉粘度破损值大，玉米淀粉破损值小、峰谷粘度高。     

不同培养时间和玉米粉浓度对三株根霉产酶活性的影响

本文对Rhizopus11、34、51三个菌株在不同培养时间和玉米粉浓度下培养产生的糖化酶、液化酶、蛋白酶的活性进行了比较研究,结果表明,Rhizopus34明显优于其他两个菌株,培养2~4d,糖化酶的活性高达1.35×102u/g(鲜曲),液化酶达3.72×103u/g(鲜曲),蛋白酶达6.34×102u/g(鲜曲)。综合不同玉米粉浓度对三种酶活性的影响,我们认为在制曲过程中以添加5~10%的玉米粉为宜。     

连续喷射液化优越于间歇液化

液化是淀粉在一定条件下,经过α-淀粉酶的作用,将淀粉分子水解到糊精和低聚糖的一种化学变化。在酿造工业中,酱油、食醋、淀粉糖的生产都离不开液化。由于淀粉乳在糊化时,淀粉乳的粘度很高。因此流动性差,给搅拌带来了困难,而且还会影响传热效果,使淀粉乳糊化难以均匀地进行,尤其当淀粉的浓度较高而料液量大的情况下,操作就更加困难,这是在现行的间歇液化中常见的情况。但是,由于α-淀粉酶对糊化的淀粉乳具有很强的液化水解作用,能     

外源淀粉对鲜湿面条品质影响

不同淀粉来源影响面条品质,为探讨外源淀粉对鲜湿面条品质影响,该实验选取6种外源淀粉作为试材,比较不同来源淀粉在相同添加量和同源淀粉在不同添加量下对鲜湿面条感官品质、蒸煮品质及TPA指标的影响,并分析外源淀粉添加对面粉糊化特性的影响。研究表明:随外源淀粉添加量增大,面条感官得分先增大后减小,面条的干物质吸水率增加,干物质损失率和熟断条率先减小后增大,面条的各TPA测定指标先增大后减小。添加6%马铃薯淀粉的混合粉制作出的面条品质较好,感官得分最高,为(93.40±2.41)分,面条的各TPA指标均最大,硬度7 411.832 g、粘着性1.917 g·s、弹性0.927、咀嚼度6 018.793、回复性0.859;添加外源淀粉后面粉糊化峰值粘度有所升高,糊化温度有所下降,其中添加6%马铃薯淀粉时的变化最显著,其糊化峰值粘度为1 860cp,糊化温度为71℃。     

Milk production and composition from cows fed high oil or conventional corn at two forage concentrations

Twelve multiparous Holstein cows (63 +/- 24 d in milk) were used in a replicated 4 x 4 Latin square with 28-d periods to evaluate conventional and high oil corn grains when fed at two different forage-to-concentrate ratios. Dietary treatments consisted of conventional or high oil corn supplementing a diet with a 25:25:50 mixture of corn silage: alfalfa: concentrate mix, or a high forage diet with a 30:30:40 mixture of corn silage: alfalfa: concentrate mix. Dry matter intake (28.1, 28.7, 26.9, and 26.2 kg/d for normal diets with conventional and high oil corn, and high forage diets with conventional and high oil corn, respectively) and milk yields (36.8, 37.2, 35.5, and 35.2 kg/d) were similar for conventional and high oil corn diets and were lower with the high forage diet, regardless of corn source. Milk fat concentrations were greater when cows were fed diets containing 60% forage (4.03 vs. 3.88%, for the 60 and 50% forages, respectively), but milk protein concentrations were not affected by forage content. Corn source did not affect milk fat or protein concentrations. Long-chain fatty acid concentrations, unsaturated fatty acid concentrations, and total 18:1 fatty acid concentrations were greater when cows were fed high oil corn but were unaffected by forage content of the diet. Concentrations of transvaccenic acid (0.58, 0.81, 0.62, and 0.69 g/100 g of fatty acids) and cis-9, trans-11 conjugated linoleic acid (0.28, 0.39, 0.32, and 0.33 g/100 g of fatty acids) were greater when cows were fed high oil compared with conventional corn when fed 50% forage but were similar for both corn sources at 60% forage. Total n-3 fatty acids were not affected by corn source or forage content. High forage diets decreased milk production and increased milk fat concentration. Feeding high oil corn increased concentrations of long-chain, unsaturated, transvaccenic, and conjugated linoleic fatty acids in milk; however, production of transvaccenic and conjugated linoleic acids were attenuated by high forage diet.     

VISCOSITY and SURFACE TENSION of CORN OIL AT FRYING TEMPERATURES

Surface active properties and viscosity changes of corn oil were determined under controlled frying conditions. Viscosity of corn oil was measured at a temperature range of 100–200C. Surface-active properties of thermally degraded corn oil were determined by measuring the stationary contact angle () of oil droplets placed on a low energy surface (polystyrene). the viscosity of oil decreased as temperature increased. At 200C, the kinematic viscosity had decreased 69% when compared with its initial value of 7.50 mm²/s at 100C. Oil was degraded by frying 400 g of potatoes for 5 min each hour for 36 h (low load frying). the experiment was repeated with 1200g of potatoes (high load frying). the viscosity of the oil increased 9.4% and 28.6% for low and high load fryings, respectively. the surface tension of the oil and its degradation time were inversely proportional (at high load frying) lowering the surface tension of the oil by 2.0%. A high correlation (r²= 0.90) between the viscosity and surface tension of oil was obtained.     

谷物牛奶复合发酵乳的发酵条件优化及贮存品质分析

以谷物小米、黑米、黑玉米与牛奶为主要原料制备谷物牛奶复合发酵乳,以感官评分为评价指标,通过单因素试验和响应面试验对其发酵工艺条件进行优化,并对其贮存品质进行分析。结果表明,谷物牛奶复合发酵乳的最佳发酵工艺条件为：谷物与水按照料水比1∶15(g∶m L)打浆,以牛奶质量为基准,谷物浆添加量20%,发酵剂添加量0.55%、白砂糖添加量6%,在42℃条件下发酵6 h。在此优化条件下,谷物牛奶复合发酵乳的感官评分为93分,p H值为4.57,酸度为81.8°T,持水力为95%,黏度为11.5(Pa·s),蛋白质含量为3.32 g/100 g,花青素含量为5.33 mg/L;在2～4℃条件下贮存的保质期为21 d,保质期内乳酸菌活菌数≥1×10⁶ CFU/m L。     

L-乳酸菌的选育及在酒糟基质中的培养

从市售酸乳、泡菜中筛选得到产L-乳酸细菌,通过NTG诱变选育和摇瓶发酵试验,选出两株利用葡萄糖较好的菌株m-58和m-16,以玉米浓醪酒糟清液为基质对2株乳酸细菌进一步驯化培养,得出m-58菌株,更能较好地发酵玉米酒：糟清液,产生乳酸,m-58菌株在48h发酵含糖63gm的玉米浓醪酒糟清液产生50gm的L-乳酸,m-58菌株适合用于发酵玉米酒糟产乳酸。     

采用膜分离法从玉米皮中制备阿魏酸的研究

采用乙醇/水/NaOH溶液从玉米麸皮中提取阿魏酸,解决了提取液粘度高而难于实现膜分离的问题。最优提取工艺为:NaOH 0.25mol/L,醇水比1∶1(v/v),料液比1∶10(w/v),提取时间2.0h,提取温度75℃,搅拌速度120r/min。膜分离工艺为:利用截留分子量为5000u的超滤膜,在室温、0.10MPa下超滤,阿魏酸透过率达86.4%;透过液用截留分子量150u的纳滤膜在0.45MPa、30℃下浓缩120min,此时料液浓缩4.3倍,阿魏酸截留率为94.3%。将纳滤浓缩液经酸化、结晶,低温干燥后获得阿魏酸含量为55.8%粗制品;粗制品得率为16.5g/kg玉米皮。      

Invited review: production and digestion of supplemented dairy cows on pasture

Literature with data from dairy cows on pasture was reviewed to evaluate the effects of supplementation on intake, milk production and composition, and ruminal and postruminal digestion. Low dry matter intake (DMI) of pasture has been identified as a major factor limiting milk production by high producing dairy cows. Pasture DMI in grazing cows is a function of grazing time, biting rate, and bite mass. Concentrate supplementation did not affect biting rate (58 bites/min) or bite mass (0.47 g of DM/bite) but reduced grazing time 12 min/d per kilogram of concentrate compared with unsupplemented cows (574 min/d). Substitution rate, or the reduction in pasture DMI per kilogram of concentrate, is a factor which may explain the variation in milk response to supplementation. A negative relationship exists between substitution rate and milk response; the lower the substitution rate the higher the milk response to supplements. Milk production increases linearly as the amount of concentrate increases from 1.2 to 10 kg DM/d, with an overall milk response of 1 kg milk/kg concentrate. Compared with pasture-only diets, increasing the amount of concentrate supplementation up to 10 kg DM/d increased total DMI 24%, milk production 22%, and milk protein percentage 4%, but reduced milk fat percentage 6%. Compared with dry ground corn, supplementation with nonforage fiber sources or processed corn did not affect total DMI, milk production, or milk composition. Replacing ruminal degradable protein sources with ruminal undegradable protein sources in concentrates did not consistently affect milk production or composition. Forage supplementation did not affect production when substitution rate was high. Fat supplementation increased milk production by 6%, without affecting milk fat and protein content. Increasing concentrate from 1.1 to 10 kg DM/d reduced ruminal pH 0.08 and NH3-N concentration 6.59 mg/dl, compared with pasture-only diets. Replacing dry corn by high moisture corn, steam-flaked or steam-rolled corn, barley, or fiber-based concentrates reduced ruminal NH3-N concentration 4.36 mg/dl. Supplementation did not affect in situ pasture digestion, except for a reduction in rate of degradation when high amounts of concentrate were supplemented. Supplementation with energy concentrates reduced digestibility of neutral detergent fiber and intake of N but did not affect digestibility of organic matter or flow of microbial N.     

酶法制备燕麦浆工艺研究

以可溶性固形物含量为指标,对α-淀粉酶酶解燕麦制备燕麦浆的工艺进行优化。结果表明,当加酶量为6u/g燕麦,温度为55℃,时间为45min,料液比为1:8(w:w)时得到的燕麦浆的可溶性固形物含量最高,达到17.24g/100mL。然后又研究了淀粉水解程度对燕麦浆粘度、色泽和稳定性的影响,发现当DE值达到50%时,燕麦浆的粘度、色泽、稳定性基本不再变化。     

Effects of feeding extruded linseed on production performance and milk fatty acid profile in dairy cows: A meta-analysis

The objectives of this study were to quantify the effects on production performance and milk fatty acid (FA) profile of feeding dairy cows extruded linseed (EL), a feed rich in α-linolenic acid, and to assess the variability of the responses related to the dose of EL and the basal diet composition. This meta-analysis was carried out using only data from trials including a control diet without fat supplementation. The dependent variables were defined by the mean differences between values from EL-supplemented groups and values from control groups. The data were processed by regression testing the dose effect, multivariable regression testing the effect of each potential interfering factor associated with the dose effect, and then stepwise regression with backward elimination procedure with all potential interfering factors retained in previous steps. This entire strategy was also applied to a restricted data set, including only trials conducted inside a practical range of fat feeding (only supplemented diets with <60 g of fat/kg of dry matter and supplemented with <600 g of fat from EL). The whole data set consisted of 17 publications, representing 21 control diets and 29 EL-supplemented diets. The daily intake of fat from EL supplementation ranged from 87 to 1,194 g/cow per day. The dry matter intake was numerically reduced in high-fat diets. Extruded linseed supplementation increased milk yield (0.72 kg/d in the restricted data set) and decreased milk protein content by a dilutive effect (?0.58 g/kg in the restricted data set). No effect of dose or diet was identified on dry matter intake, milk yield, or milk protein content. Milk fat content decreased when EL was supplemented to diets with high proportion of corn silage in the forage (?2.8 g/kg between low and high corn silage-based diets in the restricted data set) but did not decrease when the diet contained alfalfa hay. Milk trans-10 18:1 proportion increased when EL was supplemented to high corn silage-based diets. A shift in ruminal biohydrogenation pathways, from trans-11 18:1 to trans-10 18:1, probably occurred when supplementing EL with high corn silage-based diets related to a change in the activity or composition of the microbial equilibrium in the rumen. The sum of pairs 4:0 to 14:0 (FA synthesized de novo by the udder), palmitic acid, and the sum of saturated FA decreased linearly, whereas oleic acid, vaccenic acid, rumenic acid, α-linolenic acid, and the sums of mono- and polyunsaturated FA increased linearly when the daily intake of fat from EL was increased. In experimental conditions, EL supplementation increased linearly proportions of potentially human health-beneficial FA in milk (i.e., oleic acid, vaccenic acid, rumenic acid, α-linolenic acid, total polyunsaturated FA), but should be used cautiously in corn silage-based diets.     

黄原胶发酵生产培养基优化研究

黄原胶发酵生产培养基的组成对黄原胶产品质量有较大影响.通过测定发酵液粘度、粗胶含量,研究不同碳源、氮源及无机盐对黄原胶产量和粘度的影响.研究结果表明,碳源对黄原胶质量影响较大,不同碳源之间最终发酵水平有明显差别,当玉米淀粉:蔗糖2∶1时黄原胶产量和粘度最高.氮源的影响次于碳源,确定最佳氮源为黄豆粉.CaCO3能明显提高黄原胶的产量粘度,是无机盐中最大影响因子,CaCO3最优添加量为0.3g/100mL.KH2PO4影响作用不大,差别不显著,当KH2PO4添加量为0.5g/100mL时,黄原胶产量和粘度达到最大.通过正交试验,确定培养基最优配方为:玉米淀粉5g/100mL,蛋白胨0.5g/100mL,KH2PO4 0.4g/100mL,MgSO4 0.05g/100mL,FeSO4 0.025g/100mL,柠檬酸0.025g/100mL,在此条件下,28℃,180r/min发酵培养72h,黄原胶的产量可达到29.88g/L,粘度达到6002mPa/s.     

Dairy farm management practices and the risk of contamination of tank milk from Clostridium spp. and Paenibacillus spp. spores in silage,total mixed ration,dairy cow feces,and raw milk

The occurrence of Paenibacillus and Clostridium spores in silage is of great concern for dairy producers because their spores can contaminate milk and damage processed milk and semi-hard cheeses. Spoiled silage is considered to be the main contamination source of the total mixed ration (TMR), feces of dairy cows, and consequently bulk tank milk via the contamination of cow teats by dirt during milking. The presence of an anaerobic and facultative anaerobic sporeformer population in different matrices (soil, corn silage, other feeds, TMR, feces, and milk) and its transmission pathway has been studied on 49 dairy farms by coupling plate count data with 16S-DNA identification. The different matrices have shown a high variability in the anaerobic and facultative anaerobic spore count, with the highest values being found in the aerobically deteriorated areas of corn silages. Clostridium tyrobutyricum, Paenibacillus macerans, and Paenibacillus thermophilus were detected in all the matrices. The TMR spore count was influenced by the amount of spoiled corn silage in the TMR and by the care taken when cleaning the spoiled silage before feed-out. Most of the farms that prevent the presence of visible moldy silage in the silo and carefully clean to remove molded spots were able to maintain their TMR spore counts below 4.0 log spores/g. When a level of 4.5 log spores/g of TMR was exceeded, the feces presented a greater contamination than 3.0 log spores/g. Moreover, the higher the number of spores in the feces was, the higher the number of spores in the milk. Most of the farms that presented a feces contamination greater than 5.0 log spores/g had a higher milk spore contamination than 1,000 spores/L. Careful animal cleaning and good milking practices have been found to be essential to maintain low levels of contamination in bulk tank milk, but it has emerged that only by coupling these practices with a correct silage management and cleaning during TMR preparation can the contamination of milk by spores be kept at a low level. It has been found that aerobically deteriorated silage has a great capacity to contaminate TMR and consequently to increase the risk of milk spore contamination, even when routine milking practices are adopted correctly.