玉米乳酸饮料发酵过程初探

以玉米为原料进行乳酸发酵,对制备乳酸饮料的发酵过程中的动态变化作了初步分析探讨。结果显示:经过约39h的发酵,饮料中乳酸值可达2.1g/100mL,另含寡糖、氨基酸等多种营养保健成份,具可观的经济前景。对玉米乳酸饮料的生产工艺条件的进一步研究,具有一定的指导意义。     

乳酸发酵香芋饮料的研制

目的：探讨乳酸菌发酵制备香芋饮料的工艺条件。方法：通过正交实验得出发酵的最佳工艺条件。结果：保加利亚乳杆菌与嗜热链球菌最佳添加比例为1：1,发酵温度为42℃,发酵时间为36h,添加蔗糖量5％时饮料口味最佳。结论：通过乳酸菌发酵香芋汁可以制得保健型香芋饮料。     

响应面试验优化红枣乳酸发酵饮料工艺

为获得红枣乳酸发酵饮料的最佳工艺条件,以乳酸发酵饮料中的总酸含量为考察指标,在单因素试验的基础上,应用Box Behnken试验设计和响应面分析法对红枣乳酸发酵工艺进行优化,并对乳酸发酵前后的活性物质含量进行了比较。结果表明：各因素对红枣乳酸发酵饮料中总酸含量的影响大小依次为接种量、发酵温度、发酵时间,最佳工艺条件为发酵温度43℃、发酵时间24h、接种量10%,在此条件下,活性成分得到了很好地保留,制备得到的红枣乳酸发酵饮料中的总酸含量可达0.897g/100g,得到的回归模型对试验拟合较好。     

马乳酒样乳杆菌(Lactobacillus kefiranofaciens )合成开菲尔多糖培养基组成的优化

研究了发酵培养基组成对Lactobacillus kefiranofaciens的菌体生长以及合成开菲尔多糖(Kefiran)的影响。通过比较L. kefiranofaciens利用各种糖类和麦芽汁的发酵情况,发现麦芽汁最利于菌体生长及发酵产糖;各种氮源对L. kefiranofaciens发酵影响不同,其中以酵母粉最好,采用一品鲜酵母粉发酵的最佳浓度为10%;正交实验和RSA方法确定对发酵影响显著的三个无机盐是MnSO4.4H2O、MgSO4.7H2O和KH2PO4,最佳用量为0.2g/L,1g/L,4g/L,此时发酵获得开菲尔多糖产量为2.6±0.05g/L。L. kefiranofaciens发酵生产开菲尔多糖96h时可达到最佳发酵结果。     

火龙果汁发酵饮品的研制

火龙果不但营养丰富而且具有一定的保健功能。本试验以新鲜的红皮白肉型火龙果果实的榨汁为原料,分别对发酵工艺条件、蔗糖添加量、柠檬酸用量、稳定剂用量等条件进行了研究,通过单因素试验和正交试验,得到火龙果汁发酵饮料的最佳工艺配方。采用该工艺配方制备的发酵饮料澄清透明,具有清新的果香和淡淡的醇香,酸甜可口,口感顺滑。     

一种无稳定剂褐色乳酸菌饮料的研究

常规乳酸菌饮料通常使用果胶、羧甲基纤维素钠等稳定剂维持产品的稳定性,否则产品在货架期内容易出现蛋白质沉淀、分层等不稳定现象。本文中,笔者通过单因素和正交试验,以粒径为指标,研究了蛋白质含量、发酵时间和葡萄糖含量对乳酸菌饮料稳定性的影响。研究结果表明:当蛋白质质量分数为0.9%、发酵时间为60 h、葡萄糖添加量为8%时,乳酸菌饮品稳定性最佳。     

绿豆酸奶的制作工艺

绿豆酸奶是以绿豆为主要原料制作的一种新型植物蛋白乳酸饮料.本文介绍了绿豆酸奶的制作工艺及方法,通过对产品的分析证明绿豆酸奶是一种营养丰富乳酸菌饮料,含有人体必须的七种氨基酸,又含有医疗保健作用的药用成份黄酮、皂甙、鞣质,是一种较为理想的保健饮料.     

红缘拟层孔菌化学成分与药理活性研究概述

对红缘拟层孔菌的化学成分、药理活性、菌丝发酵和木质素降解作用等方面的研究进行了综述。化学成分研究表明,红缘拟层孔菌含有多种三萜类、多糖类、脑苷脂类、挥发性等成分;药理活性研究表明,红缘拟层孔菌具有抗肿瘤、抗氧化、抗糖尿病、抗炎镇痛、抑菌、保肝等药理作用;菌丝发酵研究表明,红缘拟层孔菌菌丝发酵的最佳碳源为葡萄糖,氮源为酵母膏和麦芽汁。此外,红缘拟层孔菌对纤维素有降解作用。     

麦芽根替代米糠发酵制备乳酸的研究

用啤酒厂废弃物麦芽根替代米糠或麸皮用于乳酸发酵生产不仅用量减少,产酸率提高,而且麦芽根价格比米糠便宜一倍,因此降低了乳酸生产成本。     

褐色乳酸菌饮料稳定体系的优化

为探究褐色乳酸菌饮料的体系稳定性,通过单因素和正交试验证明了葡萄糖添加量、褐变时间和发酵时间对乳酸菌饮料稳定性的影响较小;而基料添加量(蛋白质含量)、饮料pH和均质压力对稳定性的影响较大。获得褐色乳酸菌饮料最优稳定体系参数为：葡萄糖添加量80 g,褐变时间2 h,发酵时间72 h,基料添加量200 g,饮料pH 3.7,均质压力200 MPa。研究结果不仅优化了褐色乳酸菌饮料的制作工艺,而且降低了稳定剂的添加量,降低了生产成本。     

Effect of temperature and various nitrogen sources on L(+)-lactic acid production by Lactobacillus casei

 Two homofermentative strains, Lactobacillus casei NRRL B-441 and Lactobacillus casei subsp. rhamnosus NRRL B-445 were selected for further study from 17 lactic acid bacterial strains screened for lactic acid production. The effect of temperature on lactic acid production with the selected strains was investigated by adapting both strains to four different temperatures. The production of L(+)-lactic acid by both strains was most efficient at 37°C, although with L. casei the highest lactic acid concentration was obtained at 41°C. The maximal volumetric productivity with L. casei was 4.1 g l^-1 h^-1 and with L. casei subsp. rhamnosus 3.5 g l^-1 h^-1. The composition of the medium was studied in order to replace the costly yeast extract with less expensive sources of nitrogen and amino acids. From 11 different nitrogen sources investigated at 37°C, barley malt sprouts (88 g l^-1 lactic acid in 66 h) and grass extract (74 g l^-1 lactic acid in 73 h) were the best economic alternatives. The effect of different combinations of yeast extract, peptone and malt sprouts was further studied by using statistical experimental design, and an empirical second-order polynomial model was constructed on the basis of the results. With the right combination most of the yeast extract could be substituted by barley malt sprouts for efficient lactic acid production. A method for extraction of nutrients and growth factors from malt sprouts is also described. Received: 25 September 1995/Accepted: 24 October 1995     

Development of real-time PCR methods for the rapid detection of low concentrations of Gluconobacter and Gluconacetobacter species in an electrolyte replacement drink

AIMS: To develop a rapid real-time polymerase chain reaction (PCR) method to detect Gluconobacter and Gluconacetobacter species in electrolyte replacement drinks. METHODS AND RESULTS: Samples of electrolyte replacement drinks were artificially contaminated with Gluconobacter species and then filtered to collect cells. DNA was extracted from the filters and analysed by real-time PCR on the ABI Prism 7000 system, using commercial detection kits for lactic and acetic acid bacteria. In addition, specific primers and Taqman probe were designed and used for the detection of seven Gluconobacter and Gluconacetobacter species. All the assays tested demonstrated a linear range of quantification over four orders of magnitude, suggesting detection levels down to 1 CFU ml(-1) in the original drink. CONCLUSIONS: A real-time PCR method was developed to detect low concentrations of Gluconobacter and Gluconacetobacter sp. in an electrolyte replacement drink. SIGNIFICANCE AND IMPACT OF THE STUDY: Real-time PCR methods allow a rapid, high throughput and automated procedure for the detection of food spoilage organisms. The real-time PCR assay described is as sensitive as the conventional method that involves pre-enrichment, enumeration on a selective agar (typically malt extract agar) and identification with a differential medium (typically Wallerstein nutrient agar). The real-time PCR assay also provides a more rapid rate of detection, with results in less than 24 h following enrichment for Gluconobacter and Gluconacetobacter species.     

Influence of cofermentation by amylolytic Lactobacillus plantarum and Lactococcus lactis strains on the fermentation process and rheology of sorghum porridge

Amylolytic lactic acid bacteria (ALAB) can potentially replace malt in reducing the viscosity of starchy porridges. However, the drawback of using ALAB is their low and delayed amylolytic activity. This necessitates searching for efficient ALAB and strategies to improve their amylolytic activity. Two ALAB, Lactobacillus plantarum MNC 21 and Lactococcus lactis MNC 24, isolated from Obushera, were used to ferment starches in MRS broth: sorghum, millet, sweet potato, and commercial soluble starch. The amylolytic activity of MNC 21 was comparable to that of the ALAB collection strain Lb. plantarum A6, while that of MNC 24 was extremely low. MNC 21, MNC 24, and their coculture were compared to A6 and sorghum malt for ability to ferment and reduce the viscosity of sorghum porridge (11.6% dry matter). ALAB and the coculture lowered the pH from 6.2 to <4.5 within 12 h, while malt as a carrier of wild starter took about 20 h. Coculturing increased lactic acid yield by 46% and 76.8% compared to the yields of MNC 21 and MNC 24 monocultures, respectively. The coculture accumulated significantly larger (P < 0.05) amounts of maltose and diacetyl than the monocultures. Sorghum malt control and the coculture hydrolyzed more starch in sorghum porridge than the monocultures. The coculture initiated changes in the rheological parameters storage modulus (G'), loss modulus (G″), phase angle (δ), and complex viscosity (η*) earlier than its constituent monocultures. The shear viscosity of sorghum porridge was reduced significantly (P < 0.05) from 1950 cP to 110 cP (malt), 281 cP (coculture), 382 cP (MNC 21), 713 cP (MNC 24), and 722 cP (A6). Coculturing strong ALAB with weak ALAB or non-ALAB can be exploited for preparation of nutrient-dense weaning foods and increasing lactic acid yield from starchy materials.     

Growth studies of potentially probiotic lactic acid bacteria in cereal-based substrates

AIMS: The overall growth kinetics of four potentially probiotic strains (Lactobacillus fermentum, Lact. reuteri, Lact. acidophilus and Lact. plantarum) cultured in malt, barley and wheat media were investigated. The objectives were to identify the main factors influencing the growth and metabolic activity of each strain in association with the cereal substrate. METHODS AND RESULTS: All fermentations were performed without pH control. A logistic-type equation, which included a growth inhibition term, was used to describe the experimental data. In the malt medium, all strains attained high maximum cell populations (8.10-10.11 log10 cfu ml(-1), depending on the strain), probably due to the availability of maltose, sucrose, glucose, fructose (approx. 15 g l(-1) total fermentable sugars) and free amino nitrogen (approx. 80 mg l(-1)). The consumption of sugars during the exponential phase (10-12 h) resulted in the accumulation of lactic acid (1.06-1.99 g l(-1)) and acetic acid (0.29-0.59 g l(-1)), which progressively decreased the pH of the medium. Each strain demonstrated a specific preference for one or more sugars. Since small amounts of sugars were consumed by the end of the exponential phase (17-43%), the decisive growth-limiting factor was probably the pH, which at that time ranged between 3.40 and 3.77 for all of the strains. Analysis of the metabolic products confirmed the heterofermentative or homofermentative nature of the strains used, except in the case of Lact. acidophilus which demonstrated a shift towards the heterofermentative pathway. All strains produced acetic acid during the exponential phase, which could be attributed to the presence of oxygen. Lactobacillus plantarum, Lact. reuteri and Lact. fermentum continued to consume the remaining sugars and accumulate metabolic products in the medium, probably due to energy requirements for cell viability, while Lact. acidophilus entered directly into the decline phase. In the barley and wheat media all strains, especially Lact. acidophilus and Lact. reuteri, attained lower maximum cell populations (7.20-9.43 log10 cfu ml(-1)) than in the malt medium. This could be attributed to the low sugar content (3-4 g l(-1) total fermentable sugar for each medium) and the low free amino nitrogen concentration (15.3-26.6 mg l(-1)). In all fermentations, the microbial growth ceased at pH values (3.73-4.88, depending on the strain) lower than those observed for malt fermentations, which suggests that substrate deficiency in sugars and free amino nitrogen contributed to growth limitation. CONCLUSIONS: The malt medium supported the growth of all strains more than barley and wheat media due to its chemical composition, while Lact. plantarum and Lact. fermentum appeared to be less fastidious and more resistant to acidic conditions than Lact. acidophilus and Lact. reuteri. SIGNIFICANCE AND IMPACT OF THE STUDY: Cereals are suitable substrates for the growth of potentially probiotic lactic acid bacteria.     

Bacteria associated with Copestylum (Diptera, Syrphidae) larvae and their cactus host Isolatocereus dumortieri

We describe the gut bacterial diversity inhabiting two saprophagous syrphids and their breeding substrate (decayed tissues of the columnar cactus Isolatocereus dumortieri). We analyzed the gut microbiota of Copestylum latum (scooping larvae that feed on decayed cactus tissues) and Copestylum limbipenne (whose larvae can also feed on semiliquid tissues) using molecular techniques. DNA was extracted from larval guts and cactus tissues. The V1-V3 region of the 16S rRNA genes was amplified and sequenced. A total of 31,079 sequences were obtained. The main findings are: C. limbipenne is dominated by several Enterobacteriaceae, including putative nitrogen-fixing genera and pectinolitic species and some denitrifying species, whereas in C. latum unclassified Gammaproteobacteria predominate. Decayed tissues have a dominant lactic acid bacterial community. The bacterial communities were more similar between larval species than between each larva and its breeding substrate. The results suggest that the gut bacterial community in these insects is not strongly affected by diet and must be dependent on other factors, such as vertical transmission, evolutionary history and host innate immunity.     

Carnegiea gigantea: The saguaro and its uses

The saguaro,Carnegiea gigantea, is a tall cactus native to the desert area of southern Arizona and northern Sonora, Mexico. It has been used for centuries among the Indians of the region as a source of food and drink, as well as for a wide variety of other purposes. The cactus has taken a great place in the life of the Indians, most notably the Papago, who still collect the fruit and make a wine for ceremonial purposes from it. Several botanical, ethnobotanical and phytochemical studies have been made on the cactus, whose flower is the State Flower of Arizona.     

Lactic acid fermentation on barley flour without additional nutrients

Summary An amylolytic lactic acid producing Lactobacillus amylovorus produced 36 g/l of lactic acid in mixed cultures with L. casei without additional nutrients at 37 °C in 48 h, when barley flour concentration was 180 g/l (appr. 108 g/l starch) and barley malt quantity 0.8% of flour weight. This represented an improvement of up to 20% in comparison to the fermentation with L. amylovorus or L. casei alone. By simultaneous glucoamylase addition lactic acid production yield was about doubled. With L. casei the lactic acid yield was from 580 g in 72 h to 667 g in 144 h per kg barley flour.     

Use of mixed cultures for the fermentation of cereal-based substrates with potential probiotic properties

The production of a new cereal-based probiotic foods with suitable aroma, flavor and pH using mixed culture fermentation has been investigated. This required the selection of suitable types of cereal grains and probiotic microorganisms. In a medium of 5% (w/v) malt suspension the effects of yeast presence on the fermentation of a lactic acid bacterium (LAB), Lactobacillus reuteri, was studied. With different inoculum ratios between the yeast and the LAB, the characteristics of the fermentation broth including pH and the contents of free amino nitrogen (FAN), reducing sugar, lactic acid and ethanol were investigated. It was found that LAB growth was enhanced by the introduction of the yeast. In mixed culture broth pH was lowered and the production of lactic acid and ethanol were increased in comparison against pure LAB culture.     

Biological ensiling of sugarcane tops

ThreeLactobacillus leichmannii ATCC 7830 growthpromoting factors have been isolated from sugarcane tops, alfalfa and malt. These substances proved to be active also with respect to the specific lactic bacteria isolated from sugarcane tops silage. The possible role of these factors in the selection and enhancement of the activity of lactic acid producing microorganisms in the silage process is discussed.