嗜酸乳杆菌发酵大豆酸凝乳的研究

本文研究了嗜酸乳杆菌在豆乳中的生长情况,考察了温度、接种量、木瓜汁添加、嗜酸乳杆菌与植物乳杆菌复配比例对发酵的影响,最后根据发酵豆乳的感官指标,确定了嗜酸乳杆菌发酵豆乳的最佳工艺。结果表明,发酵温度为39℃、接种量为6%、木瓜汁添加量为10%、嗜酸乳杆菌与植物乳杆菌配比为1:2是制作木瓜发酵豆乳的最佳工艺条件。产品中嗜酸乳杆菌的活菌数达到3.0×109CFU/mL,且产品口感良好。     

利用复合乳酸菌发酵腊罗非鱼的工艺研究

以罗非鱼为原料,研究接种嗜酸乳杆菌和植物乳杆菌发酵腊罗非鱼的工艺技术,通过采用混合菌种对腊罗非鱼发酵工艺条件进行研究。结果表明：将罗非鱼调味腌制,均匀渗透到鱼体后,接种复合乳酸菌嗜酸乳杆菌和植物乳杆菌为发酵剂发酵腊鱼,最佳发酵工艺条件为嗜酸乳杆菌和植物乳杆菌1:1(m/m)混合、接种量2%(m/V)、发酵温度30℃、发酵时间24h。     

酸浆中嗜酸乳杆菌在豆腐废水发酵中的条件研究

从酸浆中分离得到一株嗜酸乳杆菌,并对其在豆腐废水发酵中的条件进行研究。实验结果表明:温度、初始pH、发酵时间等都影响嗜酸乳杆菌发酵产酸。采用正交试验确定了其发酵豆腐废水的最佳条件为:温度37℃;初始pH6.0;接种量6%;时间48h,在最佳条件下的产酸量可达到0.5514g/100ml。     

嗜酸乳杆菌GIM1.208产β-葡萄糖苷酶培养基及发酵条件优化

以嗜酸乳杆菌（Lactobacillus acidophilus）GIM1.208为研究对象,通过单因素、正交试验和响应面法优化其产β-葡萄糖苷酶的培养基及发酵条件。结果表明,嗜酸乳杆菌GIM1.208发酵产β-葡萄糖苷酶的最佳产酶条件为葡萄糖添加量3.0%,羧甲基纤维素钠添加量0.4%,初始pH值5.5,料液比1∶4（g∶mL）、发酵温度31 ℃,发酵时间24 h,接种量2.6%。在此优化条件下,β-葡萄糖苷酶活力为16.80 U/mL,是优化前的3.90倍。     

乳酸菌发酵蔬菜汁工艺研究

本文以胡萝卜、番茄为原料，经过加工处理，将所得的蔬菜汁用嗜酸乳杆菌和植物乳杆菌进行发酵，确定了蔬菜汁发酵的最佳比例为番茄汁：胡萝卜汁为3：1， 蔬菜汁含量为60%，确定了蔬菜汁发酵的最佳工艺参数为发酵温度32℃，嗜酸乳杆菌、植物乳杆菌接种量分别为5%、1%，发酵时间为12h。     

降胆固醇活性发酵乳杆菌F1 发酵酸乳制备条件的研究

以发酵乳杆菌F1 发酵制备酸乳,以接种量、发酵时间和发酵温度为考察因素,结合以感官评分为指标的响应面分析方法,确定发酵乳杆菌F1 发酵酸乳的最佳发酵条件为：接种量4%、发酵时间8h、发酵温度39℃。利用该条件发酵的酸乳,其胆固醇降解率达到49.16%,比优化前胆固醇的降解率提高了8.79%。     

茎瘤芥叶胡萝卜混合汁复合乳酸菌发酵饮料的研制

研制茎瘤芥叶胡萝卜混合汁复合乳酸菌发酵饮料。方法:以优质茎瘤芥叶子原汁和胡萝卜汁为原料,用嗜热链球菌、植物乳杆菌和嗜酸乳杆菌为菌种,采用单因素试验和五因素四水平正交试验,以产酸量和乳酸活菌数为指标,确定最终发酵菌种和发酵液及发酵饮料口感稳定性的最佳工艺配方。结果:用嗜热链球菌、植物乳杆菌和嗜酸乳杆菌按1:1:1比例作为发酵菌种;发酵液最佳配方为茎瘤芥叶胡萝卜混合汁配比6:4、脱脂乳4%、接种量2%、发酵温度40℃、发酵时间24h;发酵饮料最佳配方为发酵原液中添加蔗糖4%、柠檬酸0.04%、耐酸羧甲基纤维素钠(CMC-Na)0.2%、黄原胶0.03%。     

嗜酸乳杆菌发酵法制备亚油酸异构酶的研究

以正交试验确定了嗜酸乳杆菌的最佳发酵条件，对其产生的亚油酸异构酶以硫酸铵分级沉淀和Sephadex G100层析进行了分离，并测定了酶活力。结果表明，嗜酸乳杆菌适宜发酵条件为：温度40℃，初始pH6．5，接种量1％，发酵时间24h；以上条件下产生的亚油酸异构酶经纯化后测得酶活为4358．6U。     

以麦麸为原料固态发酵开发多菌种微生态制剂的研究

试验以麦麸为主要原料,采用固态发酵技术,以纳豆芽孢杆菌和嗜酸乳杆菌为发酵菌种,以活茵数为指标,通过单因素和L9(34)正交试验确定了双菌混合发酵的最佳条件.结果表明:先接入纳豆芽孢杆菌,发酵3 d后接入嗜酸乳杆菌再共同培养3 d、培养基初始含水量80%、pH值7.0、纳豆芽孢杆菌和嗜酸乳杆菌接种比例为4:6、接种量10%、发酵温度37℃的发酵效果最好.在此条件下发酵后,纳豆芽孢杆茵数为9.8×109cfu/g,嗜酸乳杆菌数为7.1×109cfu/g.     

平菇酸乳的研制

在鲜乳中添加平菇浸提液,以嗜酸乳杆菌和嗜热链球菌为发酵剂制作酸乳,通过正交试验优选出最佳组合:平菇浸提液添加量6%,菌种配比1:2,接种量2%,糖7%,使酸乳中嗜酸乳杆菌活菌数达到108 cfu/mL以上,并研究了各因素对酸乳发酵成熟、贮藏期间的影响情况.     

苜蓿最佳生育期提取叶蛋白的研究

本文选用不同生育期的苜蓿进行了叶蛋白的提取实验。结果表明在苜蓿的最佳收获为初花期，叶蛋白得率为4．49％，粗蛋白含量为60．55％。     

Partial isolation and characterisation of Medicago sativa leaf proteases

Proteolysis of leaf proteins by endogenous leaf proteases between the time of harvest and the early stages of processing accounts for substantial losses (up to 40%) in recoverable protein from Medicago sativa [lucerne (alfalfa)] leaves. To study this problem, the proteolytic enzymes from M. sativa were partially purified by ammonium sulphate fractionation and gel filtration. Carboxypeptidase, aminopeptidase and total protease activities were measured. Addition of the herbicide simazine to leaf extract inhibited the aminopeptidase and total protease activity, but had no effect on the carboxypeptidase activity. The extent of proteolysis in leaf extracts was found to be dependent on pH, temperature and time of handling and it was concluded that these factors were the most effective means of controlling proteolytic activity.     

苜蓿冰结构蛋白的提取及对冷冻面团的影响

以“肇东”紫花苜蓿干草为原料。利用磷酸盐缓冲溶液法提取苜蓿蛋白,通过单因素和响应曲面试验,得到提取苜蓿蛋白的最佳工艺条件为料液比1∶20、磷酸盐缓冲溶液浓度63 mmol/L、pH 7.7、草粉粉碎粒度80 目、搅拌时间2 h。在此条件下苜蓿蛋白的提取率为37.77%。经硫酸铵沉淀,透析脱盐,冷冻干燥后复溶,对其溶液进行冰晶形态观察,可以看出苜蓿蛋白的冰晶体积小、数量多、形态多样,说明其抑制冰晶生长及对冰晶的形态修饰效果显著,具有很好的抗冻活性,为冰结构蛋白。将其应用于冷冻面团后,冷冻面团的硬度明显降低,弹性、回复性和内聚性稍增强,咀嚼性有所降低,质地细腻柔软。     

Disappearance of cell wall monomeric components from fractions chemically isolated from alfalfa leaves and stems following in-situ ruminal digestion

Alfalfa (Medicago sativa L) leaves and stems were incubated in the rumen of an alfalfa-fed steer for 0, 12, 24 and 48 h. Residues were analysed for monosaccharides remaining in chemically isolated fractions. Pectic substances were rapidly and extensively degraded. Xyloglucans also were quite degradable, whereas glucuronoxylans were very resistant to fermentation. Cellulose disappearance was intermediate between that of xylan and xyloglucan. For all non-pectic polysaccharides, leaf material was more degradable than stem, and this difference between leaf and stem was greater for cellulose than for most hemicellulosic fractions. Acetyl groups associated with the oxalate-insoluble fractions were degraded similarly to xylans. Alkali-labile phenolic acid content was lower in stems than in leaves, but contributed only 4 g kg^?1 of leaf DM. Less than 10% of alkali-labile phenolics were associated with hemicelluloses. Structures which limit alfalfa xylan fermentation may include acetyl groups and linkages of uronic acid side chains to phenolic material.     

粉碎粒度对苜蓿不同部位茎叶营养物质及功能性质的影响

以紫花苜蓿为研究对象,对苜蓿上(大于60 cm)、中(30~60 cm)、下(0~30 cm)三部分茎叶的基本成分、活性成分、功能性质进行比较,并对不同粉碎粒度苜蓿茎叶营养物质的溶出量和功能性质进行分析。苜蓿叶中蛋白质、灰分、脂肪、维生素C、可溶性膳食纤维、多糖、多酚、总黄酮的含量,以及膨胀力、对亚硝酸钠和胆固醇的吸附能力均高于茎秆,且上部叶片最高;苜蓿茎秆中不溶性膳食纤维的含量以及持水力、持油力高于叶片。随着苜蓿上部叶片的粉碎粒度由0.20~0.25 mm减小到0.063~0.08 mm,蛋白质、多酚、总黄酮、粗多糖的溶出量分别由27.98%、12.31、6.42、20.72 mg/g增加到32.87%、13.86、7.71、22.97 mg/g;膨胀力先增大后减小,粉碎粒度为0.125~0.16 mm时达到最大,为4.40 mL/g;对胆固醇的吸附能力由2.45 mg/g (pH=2)、7.65 mg/g (pH=7)分别增加至6.01、9.66 mg/g;对亚硝酸钠的吸附能力由437.91 μg/g (pH=2)、106.43 μg/g (pH=7)分别增加至501.51、108.02 μg/g。随着苜蓿上部茎秆的粉碎粒度由0.20~0.25 mm减小到0.063~0.08 mm,持油力由4.86 g/g减小到3.44 g/g;持水力先增大后减小,粉碎粒度为0.125~0.16 mm时达到最大,为6.56 g/g。苜蓿叶片和茎秆可用于开发不同功能的食品,减小粉碎粒度可提高营养物质的溶出量,适当进行粉碎可具有更好的功能性质。     

Factors influencing antioxidant activities and total phenolic content of guava leaf extract

The aim of this study is to investigate the influence of certain factors on the yield, antioxidant activity (AA) and total phenolic content (TPC) of guava leaf extract. The effects of pretreatment of leaf sample prior to extract, extraction method, and the leaf age were investigated. Folin-Ciocalteau was used to determine the TPC. Trolox equivalent antioxidant capacity (TEAC) and equilibrium concentration (EC) were used for evaluation of AA. Results indicated that ultrasonication is the most suitable method for guava leaf extraction as it yielded the extract with the significantly highest TPC and AA. Blanching followed by ice water cooling (BCD) was suggested for the pretreatment process of guava leaves. The study of leaf maturity demonstrated that the highest activity was from the young leaves. Hot water was the best solvent to extract the active principles. The extract of BCD pretreated young leaves, extracted by hot water exhibited the highest TPC and AA with the TEAC and EC values of 24.30 ± 0.50 and 20.41 ± 0.67 mM/mg, respectively. These values are 1.88 and 8.72 times higher than the synthetic antioxidant butylated hydroxy toluene (BHT) and 1.75 and 1.21 times higher than vitamin E, respectively. It was concluded that pretreatment and drying process, method of extraction and leaf maturity played important roles on the bioactive compounds and their antioxidant power of guava leaf extract.     

Short communication: effect of tannic acid on composition and ruminal degradability of bermudagrass and alfalfa silages

We measured the effects of the addition of tannic acid on chemical composition and crude protein (CP) ruminal degradability of bermudagrass, cv. coast cross (Cynodon dactylon L.) and alfalfa (Medicago sativa L.) silages with nylon bags incubated in the rumen of two fistulated lactating cows. Silage pH was greater for alfalfa than for bermudagrass. The addition of tannic acid had no effect on silage pH. Ammonia N was greater in alfalfa than in bermudagrass silage. Treated and control silages had similar ammonia N concentrations. The percentage of CP that was solubilized at time 0 was lower for alfalfa than for bermudagrass silage. The addition of tannic acid decreased the portion of CP solubilized at time 0 and increased the potentially degradable fraction of CP. The potentially degradable fraction of CP was greater for alfalfa than for bermudagrass. There was an interaction of species and treatment; the disappearance rate of CP increased with tannic acid treatment of alfalfa but decreased with acid treatment of bermudagrass. The effective degradability of CP was similar for control and treated alfalfa but lower for treated than for control bermudagrass. Tannic acid treatment is effective in decreasing the rapidly soluble fraction of alfalfa and bermudagrass silages, which could be beneficial to the animal because it would decrease the excess of N in the rumen after feeding. Tannic acid treatment decreased CP degradability of bermudagrass silage but had no effect on alfalfa silage, suggesting that tannic acid concentration required to effectively decrease CP degradability differs among forages.     

Contribution of exopeptidases to formation of nonprotein nitrogen during ensiling of alfalfa

The experiment was conducted to investigate the exopeptidase classes in alfalfa (Medicago sativa L.) leaves, and to determine their contribution to the formation of nonprotein nitrogen (NPN) components during ensiling. Six classes of inhibitors that included bestatin (aminopeptidase inhibitor), potato carboxypeptidase inhibitor (PCI, carboxypeptidase inhibitor), 1,10-phenanthroline (dipeptidase inhibitor), diprotin A (dipeptidyl-peptidase inhibitor), butabindide (tripeptidyl-peptidase inhibitor), and dipeptide Phe-Arg (peptidyl-dipeptidase inhibitor) were used. To determine the contribution of each exopeptidase to the formation of NPN products, aqueous extracts of fresh alfalfa were fermented to imitate the proteolytic process of ensiled alfalfa and to ensure that each class of exopeptidase inhibitor would have immediate contact with the proteases in the alfalfa extract. Five classes of exopeptidases; namely, aminopeptidase, carboxypeptidase, dipeptidase, dipeptidyl-peptidase, and tripeptidyl-peptidase, were shown to be present in alfalfa leaves, each playing a different role in alfalfa protein degradation. Aminopeptidase, carboxypeptidase, and dipeptidase were the main exopeptidases contributing to the formation of NH₃-N. Among the 5 exopeptidases, tripeptidyl-peptidase appeared to be the principal exopeptidase in hydrolyzing forage protein into peptides, whereas carboxypeptidase and dipeptidase appeared to be more important in contributing to the formation of amino acid-N. Dipeptidyl-peptidase and tripeptidyl-peptidase did not play a role in the formation of NH₃-N or amino acid-N. Dipeptidase, carboxypeptidase, and tripeptidyl-peptidase were the principal exopeptidases for hydrolyzing forage protein into NPN during ensilage, and treatment with a mixture of the 5 inhibitors reduced the total NPN concentration in the fermented alfalfa extract to about 45% of that in the control after 21 d of fermentation.     

Selenium biotransformations in an insect ecosystem: effects of insects on phytoremediation

Phytoremediation of selenium-contaminated soils may be influenced by higher trophic levels including insects. We examined how selenium affects the behavior, survival, and development of the wasp parasitoid Cotesia marginiventris, parasitizing its natural host, the beet armyworm Spodoptera exigua, feeding on alfalfa, Medicago sativa, irrigated with water containing selenate. X-ray absorption spectroscopy was used to quantify the selenium chemical forms in each trophic level. Alfalfa partially transformed selenate to organoselenium. S. exigua contained only organoselenium, both directly absorbed from M. sativa and transformed from selenate. C. marginiventris cocoons collected shortly after larval emergence contained only organoselenium derived from the host. The surprising finding of trimethylselenonium-like species in adult parasitoids and the cocoons from which they emerged suggests that adults and pharates can detoxify excess selenium through methylation and volatilization. Adult parasitoids do not discriminate against selenium-containing alfalfa, even though alfalfa generates selenium volatiles. Parasitoids raised on selenium-fed larvae emerged later and pupae weighed less than their selenium-free counterparts. We conclude therefore that C. marginiventris can be used to control S. exigua damage to M. sativa being used to remove selenium from soils. Moreover, the presence of such insects may improve phytoremediation by increasing biotransformation of inorganic selenium and release of volatile selenium species.