双蛋白干酪发酵剂的筛选及发酵特性研究

为了研究不同发酵剂对牛乳或豆乳的发酵特性,对6株乳酸菌在发酵过程中的酸度、pH、胞外多糖、黏度、游离氨基氮、双乙酰等指标进行了测定。结果表明:在牛乳中,XZ3303的产酸能力最强,QH27-1滴定酸度最高;在豆乳中,QH48-3-2滴定酸度最高,并且在豆乳中的酸度明显高于牛乳。乳酸菌在豆乳中的黏度值都明显高于牛乳,并且豆乳中的黏度变化曲线有二次产黏的现象,有利于发酵乳口感的改善。XZ3303、XZ10303、QH27-1、QH48-3-2发酵乳产双乙酰能力较强;XZ3303和QH27-1产胞外多糖的能力明显高于其他菌株。通过感官分析并结合理化指标综合考虑,选择了在豆乳和牛乳中都能优势生长的L.Lactis subsp.Cremoris QH27-1和L.Lactis subsp.Lactis XZ33032株乳酸菌作为制作双蛋白干酪的发酵剂。     

Electrical conductivity as a tool for identification of metal contaminated fish protein

Fish acts as a good bioindicator for metal contamination. The contaminated metal ions are bonded into the protein biologically. The doping concentration and its properties were analyzed by the tools of electrical conductivity. For the analysis of fish species, Clarius batrachus was selected, subjected to metal-dissolved solution and studied for its muscle conductivity in both raw and pelletised forms. The various parameters analyzed were electrical conductivity and temperature dependent electrical conductivity on fish muscle protein in its unpelletised (natural) and pelletised form, when metals like copper, cadmium and lead were doped to the muscle protein. The studies carried out were atomic absorption spectroscopy (AAS), thermo gravimetric analysis (TGA) and electron paramagnetic resonance (EPR). The results showed that conductivity in muscle as well as its pelletised temperature dependent conductivity is a very good mechanism for the identification of cadmium, lead and copper contamination level.     

Yeasts as adjunct starters in matured Cheddar cheese

Debaryomyces hansenii and Yarrowia lipolytica are typical foodborne yeast species frequently associated with dairy products and capable of predominating the yeast composition in such systems. The two species fulfil a number of criteria to be regarded as co-starters for cheesemaking. They are known for their proteolytic and lipolytic activity as well as their compatibility and stimulating action with the lactic acid starter cultures when co-inoculated. Recent studies indicated that yeasts could be included as part of starter cultures for the manufacturing of cheese, enhancing flavour development during the maturation. The potential of D. hansenii and Y. lipolytica as agents for accelerated ripening of matured Cheddar cheese has been evaluated during four cheese treatments. The interaction between the two yeast species and the lactic acid bacteria was surveyed incorporating (i) D. hansenii, (ii) Y. lipolytica, (iii) both species as adjuncts to the starter culture and (iv) a control cheese without any additions for the production of matured Cheddar cheese. The physical and chemical properties of the cheeses were monitored in order to evaluate the contribution of the yeasts to cheese maturation. The yeasts grew in association with the lactic acid bacteria without any inhibition. The yeasts species when individually added contributed to the development of bitter flavours despite accelerated development of strong Cheddar flavours. When both species were incorporated as part of the starter culture, the cheese, however, had a good strong flavour after a reduced ripening period. The cheese retained this good flavour and aroma after 9 months of production. The simultaneous application of D. hansenii and Y. lipolytica as part of the starter culture for the production of matured Cheddar cheese is proposed.     

Selection of starters and a starter-mediated novel procedure for production of wara, a West African soft cheese

Summary Wara serves as an important protein source for people in West Africa. The ten most frequently isolated lactic acid bacteria from abomasum-soured milk samples were screened singly or in combinations as starter organisms for the production of wara . The screening was based on the bacteria's ability to produce lactic acid, diacetyl, β-galactosidase and an average weighted firm curd at 30 °C (6 h, 72 h). With lactic acid concentration of 10.0 g l⁻¹, β-galactosidase of 25.2 U mL⁻¹ and a firm curd weight of 16.0 g l⁻¹ milk at 30 °C, pH 5.1 after 6 h, a single-organism starter culture of Lactococcus lactis was chosen as the best suited. Compared with the commercial market samples, wara produced by this starter culture showed a 54% increase in percentage protein, 17.9% increase in ash, 23.6% increase in iron and a 150% increase in vitamin A content. Statistical analysis of sensory evaluation results showed a preference for the market sample only in terms of appearance and texture, while the starter-produced wara matched the market sample in terms of flavour and palatability. Treatment with 3% brine reduced microbial counts although dipping in 5% NaCl-in-whey gave better results in terms of the total viable count of mesophiles, psychrotrophs and coliforms compared with the untreated sample.     

The use of buttermilk as a raw material for cheese production

Buttermilk is dairy by‐product of butter production. The study aimed to analyse the quality properties of commercial buttermilk and its usefulness as a raw material for Quark cheese production. Within the study, 6 kinds of buttermilk were tested and used for cheese production. Evaluation of cheese quality included physico‐chemical, rheological and sensory analyses. Buttermilk properties were varied and corresponded with the diversification of cheese characteristics. Production yield was 17.2–22.7%, water content 68.1–75.8% and pH 4.09–4.43. The texture was diversified; however, all samples had good sensory quality. The research has shown that buttermilk is a good raw material for cheese production.     

Characterization of aromatic properties of old-style cheese starters

Old-style cheese starters were evaluated to determine their ability to produce cheese aroma compounds. Detailed analyses of the aroma-producing potential of 13 old-style starter cultures were undertaken. The proteolytic profile of the starters was established by an accelerated ripening study using a model cheese slurry and compared with those of a commercial aromatic starter and commercial Cheddar cheeses. To evaluate the aromatic potential of the starter cultures, quantification of free amino acids liberated and volatile compounds after 15 d of ripening at 30°C as well as sensory analysis were carried out. Results showed that proteolysis patterns of all 13 starter cultures in the curd model were comparable to those of commercial Cheddar cheeses. All tested cultures demonstrated the ability to produce high amounts of amino acids recognized as precursors of aroma compounds. Several differences were observed between the starters and commercial Cheddar cheeses regarding some amino acids such as glutamate, leucine, phenylalanine, proline, and ornithine, reflecting the various enzymatic systems present in the starters. Starters Bt (control) and ULAAC-E exhibited various significant differences regarding their free amino acid profiles, as confirmed by sensory analysis. In addition, identification of volatile compounds confirmed the presence of several key molecules related to aroma, such as 3-methylbutanal and diacetyl. Besides the aroma-producing aspect, 2 starters (ULAAC-A and ULAAC-H) seem to possess an important ability to generate large amounts of γ-aminobutyric acid, which contributed up to 15% of the total amino acids present in the model curd after 15 d ripening. γ-Aminobutyric acid is an amine well-known for its antihypertensive and calming effects.     

Electrical conductivity: a new tool for the determination of high hydrostatic pressure-induced starch gelatinisation

The degree of gelatinisation and electrical conductivity of wheat starch and tapioca starch suspensions (5% w/w) were determined after a pressure treatment of up to 530 MPa. With increasing pressure at a constant treatment time the degree of gelatinisation increased resulting in a gelatinisation curve similar to that of thermal gelatinisation. A pressure increase also caused an increase in electrical conductivity. A good linear relationship between the degree of gelatinisation and the electrical conductivity for both starches investigated was found. Since electrical conductivity correlates well with the degree of gelatinisation of starches after pressure treatment it is applicable for the quick and simple determination of pressure-induced starch gelatinisation.     

Characterization of the microbial community in three types of fermentation starters used for Chinese liquor production

This study examined and compared the microbial community in three typical fermentation starters (called as Daqu, Xiaoqu, and Fuqu in China) used for liquor production by analysing the 16S and 18S rRNA gene clone library. The results show that the microbial diversity in the three types of fermentation starters (JiuQu) differs significantly. The bacterial species in Daqu and Fuqu were mainly thermophilic or thermotolerant. In Daqu, the dominant bacterial species were Thermoactinomyces sanguinis (53.85%) and Pantoea agglomerans (19.23%), followed by uncultured bacteria (15.39%). The lactic acid bacterium Weissella cibaria (50%) and a member of Enterobacteriaceae, Enterobacter ludwigii (10%), were the dominant bacterial species in Xiaoqu. Low abundances of other bacteria, including Deinococcus radiodurans, Corynebacterium variabile and Acinetobacter baumannii, were reported for Xiaoqu. Enterococcus faecium, Clostridium beijerinckii and Bacillus cereus were observed in Fuqu and accounted for 46.67, 23.33 and 16.67% of the total bacteria identified, respectively. Fungal diversity was high in Daqu and consisted exclusively of thermophilic moulds, such as Aspergillus glaucus (62.5%), Thermomyces lanuginosus (12.5%) and Thermoascus crustaceus (12.5%). Only two fungal species were reported for Fuqu and Xiaoqu and both contained the mould Rhizopus oryzae. Saccharomyces cerevisiae and the non‐Saccharomyces yeast (Saccharomycopsis fibuligera) were also identified in Fuqu and Xiaoqu, respectively. This finding suggests that microbial community structure in JiuQu starters is the key factor to determine the variety of flavours. Copyright © 2015 The Institute of Brewing & Distilling     

干酪成熟过程中发酵剂的作用

介绍干酪成熟过程中乳酸菌发酵剂及二级发酵剂的作用,包括在干酪风味、质地、加速干酪成熟、产生抗菌素及营养和颜色等多方面作用,同时分析成熟期间发酵剂控制不当会引起的负面作用,提出应用具有选择性的发酵剂或经遗传修饰的发酵剂生产干酪具有较强的应用前景。     

Lactic acid fermentation as a tool for increasing the folate content of foods

Folate is an essential micronutrient involved in numerous vital biological reactions. The dietary consumption of naturally occurring vitamin B9 is often inadequate in many countries, and supplementation or fortification programs (using synthetic folic acid) are implemented to alleviate folate deficiency. Other food-based alternatives are possible, such as the use of lactic acid bacteria (LAB) to synthesize folate during fermentation. Many studies have been conducted on this topic, and promising results were reported for some fermented dairy products. However, in other studies, folate consumption by LAB or rather low folate production were observed, resulting in fermented foods that may not significantly contribute to the recommended B9 intake. In addition, the optimum conditions for folate biosynthesis by LAB are still not clear. The aim of this review was thus to (i) clarify the ability of LAB to produce folate in food products, (ii) check if the production of folate by LAB in various fermented foods is sufficient to meet human vitamin B9 requirements and (iii) suggest ways to optimize folate production by LAB in fermented food products.     

Subject: Quality problems of the cheese industry Cheese starters

Cheese starters of the mesophilic type may be single strain, multiple strain or multiple, mixed strain cultures. The difference between these starters is described. To prepare a good and active starter for cheese, the substrate-the milk-must have the right composition to ensure good growth. Also important is the equipment used for heat treatment and incubation of the starter. The modern physical forms of laboratory cultures ensure a high active starter which can be used directly as inoculation material for either bulk starter or cheese milk directly. Finally the control methods for examination of the starter activity and quality is described.     

Probiotic bacteria as adjunct starters: influence of the addition methodology on their survival in a semi-hard Argentinean cheese

Two strains of probiotic bacteria, one of Lactobacillus acidophilus and the other of Lactobacillus paracasei subsp. paracasei, were tested as adjunct cultures in cheese-making experiments, in order to assess their viability during cheese-making and ripening. The adjunct culture was added to cheese-making milk following two different methodologies: as a lyophilized powder dispersed in milk, or within a substrate composed of milk and milk fat. In all cheeses, probiotic bacteria increased a log cycle during cheese-making, and remained almost constant during ripening (60 days), always in higher number than required to meet probiotic standards. Gross composition of the cheeses was not affected by the addition of probiotic bacteria, except for pH value: cheeses with L. acidophilus added within the pre-incubated substrate, had lower pH values and were over acidified and crumbly. Direct addition of the probiotic culture was the methodology with the best performance; however the pre-incubation presented some advantages such as an increased population of lactobacilli in the initial inoculum.     

应用于羊肉脱膻的三种发酵剂筛选及发酵特性研究

为筛选出适合发酵羊肉制品的优质发酵剂,对肉葡萄球菌（Staphylococcus carnosus）、植物乳杆菌（Lactobacillus plantarum）和戊糖片球菌（Pedicoccuspentosaceus）的发酵特性进行研究,通过耐盐、耐亚硝酸盐、产酸能力、蛋白质和脂肪分解能力、膻味脂肪酸降解能力、抑菌能力、菌种间拮抗作用等试验对其筛选。结果表明,三株菌对食盐和亚硝酸盐具有较好的耐受性,能在6%的食盐溶液和150 mg/L亚硝酸盐溶液中存活,具有一定产酸能力,除植物乳杆菌无脂肪酶活性,其他两株菌具有蛋白质和脂肪降解能力,膻味脂肪酸降解率可达60%～80%,能抑制病原微生物的生长,且三株菌间无拮抗作用,对羊肉制品的风味和品质无负面影响。因此肉葡萄球菌、植物乳杆菌和戊糖片球菌可进一步应用于发酵羊肉制品的生产和开发。     

Screening of different agroindustrial by-products for industrial enzymes production by fermentation processes

Agroindustrial by-products are an abundant source of biocompounds that contain valuable nutrients, which are not exploited. In this work, lignocellulosic wastes (LW) were used in submerged fermentation (SmF) and solid-state fermentation (SSF) by Aspergillus niger NRRL3 to obtain valuable enzymes required in industries. SmF using soya bean hulls (SH), wheat bran (WB) and a by-product of wheat flour (F) produced the highest activities of endo-1,4-β-xylanase (Xyl) and endo-1,4-β-D-glucanase (EG) being at least 3 times lower than those obtained by SSF. The highest ratio of Xyl to EG was obtained in SmF with F. Xyl obtained by SmF with WB was the most thermally resistant. The enzymatic extract obtained in SmF using SH presented a high power of saccharification. The production of enzymes for further application such as bioethanol generation process revalue these LW and can help offset growing environmental problems.     

丢糟酿酒复合发酵剂的应用开发研究

针对目前白酒丢糟利用中存在的转化效率低、酒质较差等不足,通过对新型麸曲与新型大曲的研发和不同配比的探讨,得到能高效降解丢糟的复合发酵剂,其组成是新型麸曲:新型大曲=1:5。采用复合发酵剂,使丢糟中的淀粉利用率和酒精收率达到42.4%和19.8%,同时还可以得到较高质量的丢糟酒。     

Correlating mozzarella cheese properties to its production processes and microstructure quantification

Production processes influence both the composition and microstructure of cheese. Frequently the relationship between property, processing and structure has been studied empirically and the complex interactions between all parameters have not been quantified. This is often due to the limited number of production processes used to produce samples which may potentially produce biased correlations. In this study mozzarella cheeses were manufactured with a range of compositions and production processes to give three groups of cheeses with different fat contents, draining pH or calcium contents, and stretching conditions, i.e. stretching temperature and speed. Principal Component Analysis was applied to the analysis of correlations within each group of cheese samples. In this study, we found that a positive correlation exists between the diameter of fat globules and meltability, as well as free oil. In addition, we also found a positive correlation between the protein content and stretching parameters.     

Sensor fusion as a tool to monitor dynamic dairy processes

A system for monitoring milk and fat concentration in a dynamic milk/water system by fusing information from several sensors was investigated. Standard instrumentation for food production was used, the sensors were a conductivity meter, a density meter and an optical instrument used to measure backscattered light. The system was applied to a dynamic mixing situation. Prediction error did not exceed 2% in the milk concentration and 0.1% fat in the total fat concentration. The applicability of the sensor fusion approach in field conditions was demonstrated by mounting the sensors in a dairy plant and monitoring the start-up of a pasteurizer.