一种火腿肠用膏状香精的制备

结合香精调配技术和美拉德反应,通过单因素考察及正交试验,优化原料配比、工艺条件等各种影响因素,制备一种肉香浓郁、留香持久且稳定性好的火腿肠用膏状香精。研究结果表明,美拉德反应的最佳物料配比为：葡萄糖2．5g,DL-蛋氨酸1．5g,L-半胱氨酸1．0g;最佳工艺条件为：反应时间90min,反应温度103℃。     

美拉德反应制备鸡味香精的研究

以鸡肉酶解产物为原料,选择氨基酸和还原糖进行美拉德反应,确定产生最佳真鸡肉香味的反应体系所需物质配比与反应条件。研究表明在温度为100℃,反应时间90min,pH为7.5,木糖用量2g/100g,半胱氨酸用量2g/100g,硫胺素用量2g/100g,鸡油用量4g/100g产生的鱼肉风味最佳。     

响应面法优化L-抗坏血酸降解的工艺条件

以反应时间、反应温度、溶液初始pH值及L-抗坏血酸与甘氨酸物质的量比为考察因素,以L-抗坏血酸降解率为评价指标,采用响应面法优化美拉德反应中L-抗坏血酸降解的工艺条件。确定L-抗坏血酸降解的最佳条件为:反应时间146min、反应温度149℃、溶液初始pH值4.52、L-抗坏血酸与甘氨酸物质的量比1∶2,在最佳条件下,得到的L-抗坏血酸的实际降解率与预测降解率基本吻合。     

Maillard反应及其产物在烟草加香中的作用

制备了甘氨酸等18种单一氨基酸与葡萄糖进行的美拉德反应产物以及复合氨基酸粉．动物水解蛋白与葡萄糖进行的美拉德反应产物,筛选出了两组适合于烤烟加香的混合氨基酸(混合氨基酸A,混合氨基酸B),并以混合氨基酸A为例．初步研究了反应条件(pH、反应温度等)对反应产物性质(如香味特征)的影响。     

最优回归设计在美拉德反应研究中的应用

采用R415D最优回归设计,研究反应时间、糖氨比、调节pH和反应温度对美拉德反应的影响,模拟出在该实验条件下相互间的回归方程,进行了回归方程显著性检验,为继续深入研究美拉德反应提供参考。     

葡萄糖与松香胺美拉德反应产物抗氧化性能研究

通过葡萄糖与松香胺的美拉德反应可制备具有抗氧化活性的产物。研究了不同反应条件对美拉德反应产物MRPs的抗氧化性能的影响,并与常用食品抗氧化剂特丁基对苯二酚(TBHQ)进行了对比。研究表明:抗氧化能力最佳的条件是反应时间为4.5 h、温度为65℃、pH值8和葡萄糖与松香胺的物质的量之比为1:1;该条件下的产物MRPs与TBHQ的抗氧化能力接近,有望作为一种新的天然抗氧化剂。     

乳清蛋白-亚麻籽胶体系抗氧化产物的制备

以乳清蛋白为原料,亚麻籽胶为改性物,1,1-二苯基-2-苦肼基(DPPH·)自由基清除率为指标,湿热美拉德反应为改性方法,制备乳清蛋白-亚麻籽胶抗氧化产物。在单因素实验探究反应体系pH值、配比、时间及温度对乳清蛋白抗氧化活性的影响的基础上,响应面法优化分析各因素及其相互作用对乳清蛋白-亚麻籽胶抗氧化产物抗氧化活性的影响。得最佳工艺条件为:pH值10.7,m(乳清蛋白)∶m(亚麻籽胶)=2.98∶1,反应时间193.64min,反应温度为119.80℃。在此条件下,美拉德产物对DPPH·的清除率为33.48%,与未改性的乳清蛋白相比抗氧化性提高了3.36倍。经验证,此方法准确可靠,为开发乳清蛋白在食品工业中的应用以及开发新型、天然的抗氧化剂提供了参考。     

应用逐级正交优化排骨汤香精制备工艺

为了更加准确地优化排骨汤风味热反应香精的配方,降低主观误差,提高感官评价的准确度,采用由部分到整体递次优化的逐级正交优化法优化排骨汤香精的制备工艺。通过热反应原料的单因素实验,及按其在热反应中的主要贡献不同,将其分为碳源、氮源和增味3大体系。最终确定的热反应条件为:反应温度121~123℃、时间15 min、压力0.11~0.12 Mpa;优化的配方结果为:碳源体系6.000 g(D-葡萄糖5.000 g、D-木糖1.000 g);氮源体系41.770 g〔猪骨泥酶解液18.750 g、猪肉酶解液18.750 g、植物水解蛋白液1.350 g、氨基酸复合包2.920g(L-半胱氨酸0.730 g、L-谷氨酸0.730 g、L-精氨酸0.730 g、L-脯氨酸0.730 g)〕;增味体系8.532 g(硫胺素0.270 g、呈味核苷酸二钠0.162 g、酵母膏0.900 g、猪骨油7.200 g)。     

重组L-苏氨酸醛缩酶催化合成L-4-硝基苯基丝氨酸

利用pGEX-KG载体在大肠杆菌BL21(DE3)中重组表达了L-苏氨酸醛缩酶,以4-硝基苯甲醛、甘氨酸为底物酶法合成了L-4-硝基苯基丝氨酸,考察了反应温度、pH、底物摩尔比和甘氨酸浓度对酶活的影响。最佳转化条件为：反应温度45℃,pH=8.0,甘氨酸与4-硝基苯甲醛底物摩尔比5:1,底物甘氨酸最适浓度为500 mmol/L;0.1 g湿细胞菌体在10 mL反应体系中在最佳反应条件下反应24 h,底物4-硝基苯甲醛转化率为43%,产物L-4-硝基苯基丝氨酸达到9.72g/L,总收率为35%。     

木薯秸秆木质纤维素的预处理研究

对木薯秸秆稀酸预处理条件进行了优化研究.考察了液固比、反应温度、盐酸体积分数、反应时间对水解液还原糖浓度的影响.结果表明,在液固比为40:1、反应温度为100℃、盐酸体积分数为3%、反应时间为5 h的优化条件下,水解液中还原糖浓度达9.35 g·L-1.     

Influence of Spray Drying Conditions on Physicochemical Properties of Chicken Meat Powder

The influence of spray-drying conditions on the physicochemical properties of chicken meat hydrolysate powder was studied in this work. Enzymatic reaction, using Alcalase® (Novozymes, Bagsvaerd, Denmark), was carried out at 52.5°C, 4.2 g enzyme/100 g protein, and pH of 8.0 to obtain protein hydrolysate. The spray drying was carried out on a laboratory spray dryer and maltodextrin 10DE was used as carrier agent. A central composite rotatable design was used to evaluate the effect of the independent variables inlet air temperature, feed flow, and maltodextrin concentration on the responses powder moisture content, bulk density, mean particle diameter, and hygroscopicity. All variables had a significant effect on the properties and morphology of protein hydrolysate powder.     

Effect of Reaction Conditions on the Volatile Pyrazines Components of Defatted Flaxseed Meal in the Maillard Reaction System

Defatted flaxseed meal, as a high-protein by-product can be used as a good raw material for the Maillard reaction (MR). A MR model system was established using glucose, fructose, and glucose/fructose (1:1) to produce volatile compounds typically obtained from defatted flaxseed meal protein hydrolysate; these compounds were analyzed using head-space solid phase microextraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC–MS). From the 12 MR model reaction groups, the production of pyrazines was between 12.76% and 26.56%. In the 1G group (the group prepared using DH₁ = 7.87% with a glucose concentration of 10%), the amount of pyrazines generated reached 26.56%, and this was higher than that of the other 11 model reaction groups. The effect of reaction temperature (100–150 °C), reaction time (10–60 min), and sugar concentration (5–30%) on pyrazine content was determined using the 1G group. The results of this study indicated that the effect of temperature on pyrazine production was higher than that exerted by reaction time and glucose addition. The pyrazine content reached the maximum at a reaction temperature of 140 °C. The degree of reaction and pH value were also determined; the results demonstrated that accumulation of pyrazines was suboptimal when the pH of the system was dramatically decreased. For the overall reaction, the pyrazine content remained similar to that of the final products; however, the pyrazine content exhibited little correlation with the intermediate products in the MR.     

Bioconversion of corn stover hydrolysate to ethanol by a recombinant yeast strain

Three corn stover hydrolysates, enzymatic hydrolysates prepared from acid and alkaline pretreatments separately and hemicellulosic hydrolysate prepared from acid pretreatment, were evaluated in composition and fermentability. For enzymatic hydrolysate from alkaline pretreatment, ethanol yield on fermentable sugars and fermentation efficiency reached highest among the three hydrolysates; meanwhile, ethanol yield on dry corn stover reached 0.175 g/g, higher than the sum of those of two hydrolysates from acid pretreatment. Fermentation process of the enzymatic hydrolysate from alkaline pretreatment was further investigated using free and immobilized cells of recombinant Saccharomyces cerevisiae ZU-10. Concentrated hydrolysate containing 66.9 g/L glucose and 32.1 g/L xylose was utilized. In the fermentation with free cells, 41.2 g/L ethanol was obtained within 72 h with an ethanol yield on fermentable sugars of 0.416 g/g. Immobilized cells greatly enhanced the ethanol productivity, while the ethanol yield on fermentable sugars of 0.411 g/g could still be reached. Repeated batch fermentation with immobilized cells was further attempted up to six batches. The ethanol yield on fermentable sugars maintained above 0.403 g/g with all glucose and more than 92.83% xylose utilized in each batch. These results demonstrate the feasibility and efficiency of ethanol production from corn stover hydrolysates.     

Influence of Carrier Agents on the Physicochemical Properties of Mussel Protein Hydrolysate Powder

The objective of this work was to evaluate the influence of carrier agents, maltodextrin 10 dextrose equivalent (DE) and gum arabic, on the physicochemical properties of mussel meat protein hydrolysate powder produced by spray drying. Hydrolysate was obtained by enzymatic hydrolysis using Protamex (Novozymes, Bagsvaerd, Denmark) and was carried out at 51°C, 4.5 g enzyme/100 g protein, and pH 6.85. The hydrolysate, without and with 15 and 30% of carrier agent, was spray dried at 180°C inlet air temperature and 0.8 L/h feed flow rate. Moisture content, hygroscopicity, particle size, glass transition temperature, morphology, antioxidant capacity, and volatile loss of powders were evaluated. Powder moisture content decreased with the increase in carrier agent concentration. Glass transition temperature increased with carrier agent addition and consequently powder hygroscopicity was reduced, increasing its physical stability. Higher feed solution viscosity was obtained for 30% of maltodextrin and 15 and 30% of gum arabic. The particles obtained from these solution presented a greater number of dents and larger particle size. The use of carrier agents reduced volatile loss and preserved the powder's antioxidant capacity.     

糖醋排骨风味香精制备工艺的研究

为制备糖醋排骨风味香精,以排骨汤热反应香精配方为基础,通过单因素试验、正交试验和感官评价,确定糖醋排骨风味香精的最佳工艺配方为：龙门米醋9.30g、蔗糖7.30g、葡萄糖5.00g、木糖1.00g、酵母膏0.90g、猪骨油7.20g、植物水解蛋白液（HVP液）1.35g、呈味核苷酸二钠（I G）0.16g、硫胺素（VB1）0.27g、半胱氨酸0.73g、谷氨酸 0.73g、精氨酸0.73g、脯氨酸0.73g、番茄酱3.50g、花椒油1.00g、红烧酱油2.30g、料酒3.00g、辛香料复合包添加量为香精整体质量的0.10%、猪骨泥酶解液18.75g、猪肉酶解液18.75g。     

Production of polyhydroxyalkanoates by batch and fed-batch cultivations of <Emphasis Type="Italic">Bacillus megaterium</Emphasis> from acid-treated red algae

Polyhydroxyalkanoates (PHAs) are linear polyesters synthesized by microbial fermentation of various substrates. PHAs are accumulated in microbial cells in order to store carbon and energy for future use. We used acid-pre-treated red alga (Gelidium amansii) as a cheap, abundant carbon source to produce PHA via batch and fed-batch cultivation of Bacillus megaterium KCTC 2194. After acid treatment of 10% (w/v) G. amansii, 25.5 g/L galactose, 3.6 g/L glucose, 6 g/L 5-HMF, and 1.05 g/L levulinic acid were formed. In batch culture at pH 7, the dry cell weight (DCW) and PHA content increased to 5.5 g/L and 51.4%, respectively. The cell concentration was enhanced by fed-batch cultivation using two feeding strategies: pH-stat and intermittent feeding. When the pH-stat feeding strategy was employed to add concentrated hydrolysate to the fermentor, DCW increased to 8.2 g/L, with 53.2% PHA content. When concentrated hydrolysate was fed using the intermittent feeding strategy, higher DCW (10.1 g/L) was obtained, along with a slight increase of PHA content to 54.5%. This study demonstrates that red algae could be used after simple acid treatment, to produce PHA without steps for enzymatic hydrolysis and inhibitor removal.     

CNTF工程菌培养及产物纯化

目的 建立ＣＮＩＦ生产工艺，获得高产量的ＣＮＴＦ活性蛋白质。方法 通过摇瓶和发酵罐培养研究 了培养基成分、ｐＨ、诱导时间对工程菌 ｐＢＶ２２０－ＣＮＴＦ／ＤＨ５Ａα生成和表达的影响，并对表达产物进行纯化和生物学活 性检测。结果 应用正交试验确定了培养基成分配比为酵母粉１０ｇ／Ｌ，葡萄糖８ｇ／Ｌ，ＭｇＳＯ４０．５ｇ／Ｌ，磷酸盐０．０５ｍｏｌ／Ｌ， ｐＨ７．４时最有利于工程菌的生长及ＣＮＩＴ的表达。ＣＮＴＴ纯化后纯度达９５％以上，并具有较高的生物学活性。结论 为ＣＮＴＦ的结构和功能的研究及临床应用打下基础。     

天然鸡肉香精的制备与评价

根据Maillard反应原理 ,通过正交实验对天然鸡肉味香精的制备进行了研究 ,遵循以下反应条件可以得到较满意的结果 :m(氨基酸 )∶m(葡萄糖 ) =4∶1 ,m(甘氨酸 )∶m(丙氨酸 ) =1∶2 ,热反应温度 1 30℃ ,热反应时间 40min ,含水量w(H2 O) =40 % ,鸡肉蛋白使用Flavorzyme酶水解。并且对评价方法作了简单介绍。     

双酶级联生物合成D-赖氨酸

建立了氨基酸消旋酶和赖氨酸脱羧酶双酶级联高效生产D-赖氨酸的方法。利用氨基酸消旋酶全细胞催化消旋L-赖氨酸得到DL-赖氨酸,去除氨基酸消旋酶后再加入赖氨酸脱羧酶,将消旋产物中的L-构型脱羧生成1,5-戊二胺和CO2,剩下D-赖氨酸;最终,通过阳离子交换树脂吸附洗脱得到D-赖氨酸。经考察双酶级联催化的最佳条件为:反应温度40℃,0.2 mol/L磷酸钾缓冲溶液(p H=5.8),底物L-赖氨酸质量浓度为50 g/L,氨基酸消旋酶全细胞和赖氨酸脱羧酶全细胞质量浓度均为10 g/L,4 mmol/L磷酸吡哆醛,0.1 g/L Triton X-100,反应时间12 h,其中消旋反应2 h和脱羧反应10 h,最终D-赖氨酸收率达42%,对映体过量值(e.e.值)=98%。     

Swollenin pre-conditioning: optimization studies and application aiming at d-lactic acid production from sugarcane bagasse

The enzymatic hydrolysis still stands as a challenge regarding the use of renewable feedstocks, as well as of lignocellulosic materials. The present work reports optimization of swollenin addition to pretreated sugarcane bagasse, in a step prior to the enzymatic hydrolysis, named pre-conditioning. Also, it describes further fermentation of the hydrolyzed material to d-lactic acid. Trichoderma harzianum enzymatic cocktail was produced from pretreated sugarcane bagasse, while swollenin was produced using Aspergillus niger as a host for recombinant protein expression. For pre-conditioning optimization, a Central Composite Rotatable Design was applied and validated. The optimized conditions were used to produce the hydrolysate that was fermented to D-lactic acid by Lactobacillus coryniformis subsp. torquens. It could be observed that pre-conditioning effectively leads to improvements in glucose release: 62% of hydrolysis efficiency. Besides, it was possible to use the produced hydrolysate to obtain d-lactic acid, with a yield of 1.34?g/g and a productivity of 1.59?g/L h^?1.