中性蛋白酶水解啤酒槽中蛋白质的研究

以啤酒厂主要副产物啤酒糟为主要的原料,利用中性蛋白酶对其蛋白质进行水解,研究了酶解的pH温度、固液比、时间和加酶量对水解程度的影响,确定了最佳的影响因素。     

麦糟的综合利用研究

麦糟是啤酒工业的主要副产物,是麦芽、辅料的粉碎物经糖化、过滤后的滤渣,含有丰富的多糖（纤维素、半纤维素）、木质素、蛋白质等。麦糟含水量高,营养丰富,容易染菌变质,因此,对麦糟的利用主要以生产动物饲料为主,综合利用率低,产生的附加值小。麦糟中含有的多糖和蛋白质等,具有潜在的应用价值。该文综述了麦糟在饲料工业、食品工业、污水处理、培养基等方面的应用,为进一步开发麦糟的使用领域、提高麦糟的经济效益提供参考。     

啤酒糟中细菌的分离鉴定及其在啤酒糟发酵中的应用

该研究采用传统培养分离法从啤酒糟中分离细菌,通过形态观察及分子生物学技术对其进行菌种鉴定,选择其中3株细菌发酵啤酒糟,并与常规发酵真菌黑曲霉（Aspergillus niger）和出芽短梗霉（Aureobasidium pullulans）对比,以期获得对啤酒糟降解效果较好的细菌。结果表明,从啤酒糟中共分离得到6株细菌（编号为B1～B6）,经鉴定,分别为蜡样芽孢杆菌（Bacillus cereus）、梭状菌属（Clostridium sp.）、解淀粉芽孢杆菌（Bacillus amyloliquefaciens）、贝莱斯芽孢杆菌（Bacillus velezensis）、暹罗芽孢杆菌（Bacillus siamensis）、枯草芽孢杆菌（Bacillus subtilis）。其中解淀粉芽孢杆菌B3对啤酒糟的降解效果最好,且优于常规真菌,其发酵啤酒糟的蛋白质、总还原糖、阿魏酰低聚糖含量、木聚糖酶酶活、羧甲基纤维素酶酶活均最高,分别为25.26%、3.92%、10.01μmol/L、803.59 U及38.16 U。     

啤酒糟在国内外食品加工中的利用现状

啤酒糟是啤酒酿造的最主要副产物,含有丰富的蛋白质和非淀粉多糖.随着啤酒原料中小麦芽使用量的增加(≥40％),啤酒糟中膳食纤维和蛋白质的含量明显增加.目前啤酒糟主要用作饲料或工业原料出售,但在食品加工中的应用研究较少.本文通过概述啤酒糟的营养、加工处理方法及其在国内外食品加工领域中的研究利用情况,为高蛋白膳食纤维啤酒糟食品的进一步开发提供了参考.     

啤酒糟酸奶的研制

以牛乳为主要原料,添加啤酒糟等成分,经过乳酸菌发酵而制成的一种富含膳食纤维的酸奶。以啤酒糟酸奶的感官品质和理化检测数据为评价指标,利用正交试验和模糊综合评价法得到最适宜的配方及工艺参数：啤酒糟添加量4%,果葡糖浆添加量10%,发酵温度42 ℃,发酵时间10 h。在此优化条件下,啤酒糟酸奶的感官评分为38.5分,酸度为84.8 °T,蛋白质含量为2.6 g/100 g、脂肪含量为2.5 g/100 g,成品风味独特,酸甜适口,是一种极具开发价值的保健酸奶。     

出芽短梗霉固态发酵啤酒糟制备阿魏酰低聚糖和膳食纤维工艺研究

以啤酒糟为试验材料,研究固态发酵制备阿魏酰低聚糖和膳食纤维的最佳发酵工艺条件。以阿魏酰低聚糖和可溶性膳食纤 维含量为评价指标,选择木聚糖、尿素、磷酸二氢钾为影响因素,通过正交试验确定最佳固态培养基配方。在接种量、发酵时间和发酵 温度3个单因素试验的基础上,利用响应面法优化出芽短梗霉发酵啤酒糟的发酵工艺条件。结果表明,固态发酵的最佳培养基配方为 木聚糖6%、尿素4%和磷酸二氢钾1%;最佳固态发酵条件为接种量12%、发酵时间4 d和发酵温度29 ℃。在此优化条件下,阿魏酰低聚 糖含量和可溶性膳食纤维含量都达到最高,分别为37.67μmol/L和23.76%。     

Acid hydrolysis and fermentation of brewer's spent grain to produce xylitol

The hemicellulosic fraction of brewer's spent grain (BSG) was hydrolysed with diluted acid under different conditions of liquid/solid ratio (8–12 g g⁻¹), sulfuric acid concentration (100–140 mg g⁻¹ dry matter) and reaction time (17–37 min) in order to produce a liquor with a large amount of xylose and good fermentability to produce xylitol. Results showed that all the evaluated reaction conditions were able to hydrolyse xylan and arabinan with efficiencies higher than 85.8 and 95.7% respectively, and even under the mildest reaction condition a considerable amount (92.7%) of the hemicellulosic fraction could be extracted. The hydrolysates presented different fermentabilities when used as fermentation media for xylitol production by Candida guilliermondii yeast, owing to the differences in their composition. Based on statistical analysis, the best condition for BSG acid hydrolysis was the use of a liquid/solid ratio of 8 g g⁻¹, 100 mg H₂SO₄ g⁻¹ dry matter and a reaction time of 17 min. Under this condition a high extraction efficiency of hemicellulosic sugars (92.7%) and good fermentation results (Y_P/S = 0.70 g g⁻¹ and Q_P = 0.45 g dm⁻³ h⁻¹) were attained. Copyright © 2005 Society of Chemical Industry     

Brewer’s spent grain as a functional ingredient for breadsticks

Brewer’s spent grain (BSG) was evaluated for its potential as a functional baking ingredient. Scanning electron microscopy (SEM) was used to examine the microstructure of BSG and wheat flours. Baked snacks (breadsticks) were prepared using 15%, 25% and 35% BSG and evaluated for their baking quality and fibre and protein content (over a period of 3 months). The addition of BSG altered the baking characteristics of the breadsticks by affecting their structure and texture. The snacks appeared to lack in cellular structure and crispiness. However, they had quite a stable shelf‐life, as changes in texture, moisture and a_w progressed at a low rate. Addition of 25% and 35% BSG significantly increased the protein content of the snacks, and addition of 15% BSG more than doubled the content of dietary fibre in the samples.     

Lactic acid fermentation of brewer's spent grain hydrolysate by Lactobacillus rhamnosus with yeast extract addition and pH control

Lactic acid (LA) is a versatile chemical with a wide range of applications in food, pharmaceutical, cosmetic, textile and polymer industries. Brewer's spent grain (BSG) is the most abundant brewing by‐product. In this study BSG hydrolysates were used for LA fermentation by Lactobacillus rhamnosus ATCC 7469. The aim of this study was to evaluate the effects of pH control during fermentation, reducing sugar content and yeast extract content in BSG hydrolysate on LA fermentation parameters. The pH control greatly increased reducing sugar utilization, l ‐(+)‐LA content, yield and volumetric productivity. The highest l ‐(+)‐LA yield and volumetric productivity were achieved with the reducing sugar content of 54 g/L. Yeast extract addition significantly increased reducing sugar utilization, l ‐(+)‐LA content, L. rhamnosus cell viability, l ‐(+)‐LA yield and volumetric productivity. The highest l ‐(+)‐LA content (39.38 g/L), L. rhamnosus cell viability (9.67 log CFU/mL), l ‐(+)‐LA yield (91.29%) and volumetric productivity (1.69 g/L/h) were achieved with the reducing sugar content of 54 g/L and yeast extract content of 50 g/L. Copyright © 2017 The Institute of Brewing & Distilling     

啤酒糟挥发油化学成分的GC-MS分析及对DPPH自由基的清除作用

采用水蒸气蒸馏法提取啤酒糟挥发油,利用气相色谱-质谱联用法（GC-MS）分析挥发油的化学成分,并以面积归一化法测定各成分的相对含量。从挥发油中共鉴定出38个化合物,占挥发油总量的91.09%,含量较高的成分有棕榈酸（48.90%）、亚油酸（26.10%）、肉豆蔻酸（3.02%）、硬脂酸（2.74%）、糠醛（1.47%）、苯乙醛（0.94%）。利用分光光度法测定啤酒糟挥发油对DPPH自由基的清除作用,其清除作用明显,清除率与样品量呈量效关系,25%挥发油IC50值为50.53μL。      

啤酒糟发酵应用

啤酒糟是微生物发酵的良好基质,利用微生物发酵啤酒糟的用途非常广泛.啤酒糟的再利用,有利于保护生态环境和节约资源.综述了近年来国内外啤酒糟在酶制剂、动物饲料、活性物质、食品添加剂方面的发酵应用.     

啤酒糟苹果醋不同发酵阶段挥发性香气成分及抗氧化性变化分析

采用顶空固相微萃取（HS-SPME）结合气质联用（GC-MS）法测定啤酒糟苹果汁、苹果酒、苹果醋的挥发性成分,探究啤酒糟苹果醋不同发酵阶段挥发性香气成分及抗氧化性变化。结果表明,苹果醋不同发酵阶段样品共检测出50种挥发性化合物,其中酯类16种、醇类8种、醛类8种、酸类7种、酚类4种、其他类4种、酮类2种、醚类1种。啤酒糟苹果汁、苹果酒、苹果醋中分别共检测出12种、15种、24种挥发性物质。抗氧化活性试验结果表明,DPPH自由基的清除率顺序为啤酒糟苹果酒＞啤酒糟苹果汁＞啤酒糟苹果醋,Fe3+还原能力顺序为啤酒糟苹果汁＞啤酒糟苹果酒＞啤酒糟苹果醋。     

Effects of Brewer's Spent Grain on the Quality and Dietary Fibre Content of Cookies

Dried and ground brewer's spent grain (BSG) was blended with soft wheat flour at levels of 5–25%. BSG preparations of fine (<212 μm), medium (212–425 μm) and coarse (425–850 μM) particle sizes were used in the production of wire‐cut cookies. The protein content decreased and the dietary fibre content (acid detergent fibre, neutral detergent fibre and total dietary fibre) increased, as the particle size of the BSG samples increased. The results indicated that BSG preparations with high dietary fibre content have potential as a source of dietary fibre. The effects of BSG on the quality and dietary fibre content of cookies have been investigated. Total dietary fibre (TDF) contents of the cookies supplemented with different particle size BSG increased significantly (p<0.05) as the addition level increased. Cookies prepared with BSG of medium and coarse particle sizes resulted in better properties in terms of Spread Ratio, Hunter color values and overall sensory score as compared to those made with BSG of fine particle size. Cookies made with medium and coarse particle size BSG gave better cookie properties up to the 15% addition and deteriorated significantly above this level (p<0.05).     

Grape seed flour is a viable ingredient to improve the nutritional profile and reduce lipid oxidation of frankfurters

In this study, grape seed flour (GSF) obtained from wine by-products was incorporated into frankfurters at seven concentrations (0, 0.5, 1, 2, 3, 4, and 5%) and the effects occurred on physical, nutritional and sensory characteristics of the products were investigated. The colour values (L*, a* and b*) of frankfurters generally decreased (p < 0.05) on account of the increasing amount of GSF. The utilization of this flour also led to a decline in the oxidation level of the products (p < 0.05), probably due to its antioxidant content. The increment of GSF in the frankfurters enhanced the protein, total dietary fibre and water holding capacity of the treatments (p < 0.05). Although the level of GSF above 0.5% reduced overall acceptability, the frankfurters containing the level up to 2% received scores above the average. The evaluation of wine by-products in the production of healthier and functional frankfurters has been achieved by the study, but further research is necessary to improve palatability of the products.     

Fed‐batch l‐(+)‐lactic acid fermentation of brewer's spent grain hydrolysate

Brewer's spent grain (BSG) hydrolysates were used for l ‐(+)‐lactic acid (LA) fermentation by Lactobacillus rhamnosus ATCC 7469. The aim of this study was to evaluate fed‐batch LA fermentation of BSG hydrolysate with the addition of glucose, glucose and yeast extract, and wort during LA fermentation and its effect on fermentation parameters such as LA concentration, its volumetric productivity and yield, and L. rhamnosus cell viability. The highest LA yield, volumetric productivity and concentration of 93.3%, 2.0 g/L/h, and 116.1 g/L, respectively, were achieved with glucose and yeast extract addition during fermentation. In fed‐batch fermentation with glucose and yeast extract addition significantly higher LA concentration, yield and volumetric productivity (by 194.8; 2.2, and 20.7%, respectively) were achieved compared with batch fermentation. The results indicated that fed‐batch fermentation could be used to increase LA fermentation efficiency. Copyright © 2017 The Institute of Brewing & Distilling     

Quantitative determination of fluorine in spent grain and brewery yeast

Previously published studies have shown that fluorine could present a health risk for humans. In this context, legislative regulations define the fluorine limits in many commodities, including brewery by‐products, such as spent grain and brewery yeast used as a feed. A method for the determination of fluorine in these by‐products using gas chromatography with flame ionization detection is therefore proposed. The first step is based on extraction of fluorine with 1 mol/L hydrochloric acid solution simulating acidic stomach surroundings. Then, fluorine is derivatized by trimethylchlorosilane to form trimethylfluorosilane (TMFS), which is subsequently extracted in liquid–liquid mode. TMFS is then analysed by gas chromatography–flame ionization detection; n‐pentane is used as an internal standard for fluorine quantification. The recovery of the method was >96%. The results also showed a high correlation coefficient (R > 0.999) in the calibration range studied (0–2000 mg/kg). The precision of the method, expressed as the relative standard deviation, was 13%. The limit of quantification was 0.02 mg/kg. This method was used for pilot screening of fluorine in 16 grain and 12 yeast samples. The resulting concentrations of fluorine ranged between 1.5 and 20.0 mg/kg, levels far below the legislative limits. Copyright © 2015 The Institute of Brewing & Distilling     

Characterisation of protein‐rich isolates and antioxidative phenolic extracts from pale and black brewers' spent grain

Protein‐enriched isolates and co‐product fractions were obtained from sheared, pale and black brewers' spent grain (BSG) using sequential aqueous and alkaline (110 mm NaOH) extraction, followed by isoelectric precipitation at pH 3.8. A recovery of 59% of the original pale BSG protein and 15% of the black BSG protein was obtained for the final isolates. Gel permeation HPLC (GP‐HPLC) revealed that 59% of the extracted pale BSG protein and only 6% of black BSG protein had a molecular mass >10 kDa. Glutamine/glutamate and proline were the most abundant amino acids present in both isolates. Analysis of four co‐product fractions obtained during fractionation from both pale and black BSG revealed the presence of phenolics, with higher concentrations in the black BSG extracts. These fractions possessed antioxidant and free radical scavenging activity when tested using the ferric reducing ability of plasma (0.16 ± 0.01 to 4.33 ± 0.11 mg Trolox equivalents g^?1 BSG dry weight) and diphenylpicrylhydrazyl (12.85 ± 1.16% to 59.50 ± 3.47% DPPH?_sc) assays, respectively. The protein‐enriched isolates and the phenolic‐rich extracts may find use as value‐added ingredients for incorporation into conventional and functional foods.     

Antioxidant capacity,arabinoxylans content and in vitro glycaemic index of cereal-based snacks incorporated with brewer's spent grain

Extruded snacks and breadsticks were formulated with increasing levels of brewer's spent grain (BSG). The phenolic content increased by 4 and 7 fold with BSG addition in extrudates (40 g/100 g) and in breadsticks (35 g/100 g), respectively. Consequently, antioxidant capacity (DPPH, FRAP) also increased despite a recorded loss of phenolic compounds in extruded snacks. Arabinoxylans content increased up to 20 and 25 g of BSG addition/100 g of formulated extruded snacks and breadsticks, respectively. Further addition of BSG did not improve the content of arabinoxylans due to the possible formation of polysaccharide–protein complexes. Medium GI breadsticks were obtained with 35 g of BSG incorporation/100 g formulation. Phenolic content, arabinoxylans content and antioxidant capacity increased in the final products with BSG addition while the glycaemic response decreased. BSG can be incorporated as an ingredient in the formulation of extruded snacks and breadsticks generating products richer in antioxidants and fibre and with low GI.