酸奶及其营养保健作用

<正> 发酵乳制品种类繁多,世界各国和不同民族,均有其传统的产品,但以市售酸奶的产量及需求最大,普及面最广。 定义和工艺 酸奶被联合国粮农组织和世界卫生组织定义为:以鲜牛奶或奶粉为原料,经过预处理,然后接入纯粹培养的保     

The relative effect of milk base, starter, and process on yogurt texture: a review

Yogurt is a milk curd produced all over the world, obtained by a lactic fermentation of a milk base enriched with milk proteins, and sometimes sugars and thickeners. One of the most important sensorial attributes for yogurt is texture, which could be assessed by sensory or instrumental analysis. A lot of work has been published in studying the contribution of milk base, starter, and process on yogurt texture in order to develop new textures, or simply to reduce fat content, or the level of addition of protein and thickener in milk. However, these studies are limited to only a few factors. The topic of this review was to synthesize the data of literature, with the aim of extracting and classifying factors on the basis of their influence on yogurt texture. Three factors, milk base heating, starter, and yogurt shearing after fermentation, respectively, play a key role in the elaboration of texture. The control of these three parameters allows the improvement of the textural attributes of yogurts by 2 to 15 times.     

酸奶粉生产技术的研究进展

酸奶粉具有丰富的营养价值，在医疗和食品工业中得到了广泛的应用。酸奶粉既保持了酸奶原有的营养价值和功能特性，又延长了货架期、降低了成本，因此具有广阔的发展前景。从酸奶粉的干燥方法、再水合以及保护剂等角度阐述了酸奶粉的生产工艺，并进行了展望。     

Amylose–Potassium Oleate Inclusion Complex in Plain Set‐Style Yogurt

Health and wellness aspirations of U.S. consumers continue to drive the demand for lower fat from inherently beneficial foods such as yogurt. Removing fat from yogurt negatively affects the gel strength, texture, syneresis, and storage of yogurt. Amylose–potassium oleate inclusion complexes (AIC) were used to replace skim milk solids to improve the quality of nonfat yogurt. The effect of AIC on fermentation of yogurt mix and strength of yogurt gel was studied and compared to full‐fat samples. Texture, storage modulus, and syneresis of yogurt were observed over 4 weeks of storage at 4 °C. Yogurt mixes having the skim milk solids partially replaced by AIC fermented at a similar rate as yogurt samples with no milk solids replaced and full‐fat milk. Initial viscosity was higher for yogurt mixes with AIC. The presence of 3% AIC strengthened the yogurt gel as indicated by texture and rheology measurements. Yogurt samples with 3% AIC maintained the gel strength during storage and resulted in low syneresis after storage for 4 wk.     

Influence of lactose concentration of milk and yogurt on growth rate of rats

Growth rates of rats fed lyophilized diets of yogurt, milk, 100% lactose-hydrolyzed milk, and 100% lactose-hydrolyzed yogurt were compared. No differences were significant in weight gains between the animals fed lactose-hydrolyzed diets over 3 wk. Further more, rats fed the lactose-hydrolyzed diets had significantly larger weight gains during the 1st wk than those fed unhydrolyzed diets. This may have been from the deleterious effect of lactose, which was in concentrations of 43% in milk and 36% in yogurt. However, by the 2nd wk, rats fed yogurt had growth rates similar to those fed lactose-hydrolyzed diets, and by the 3rd wk, no differences of growth rates were significant. Continued consumption of high concentrations of lactose improved digestion of lactose. Yogurt fermentation produced growth benefit as compared to the milk from which it was made by reducing the lactose content and by supplying microbial lactase activity.     

温故知新——回眸2005年中国酸奶市场

<正>酸奶因其营养价值高、口感好、低乳糖易于亚洲人群吸收等特质,已经受到越来越多国人的青睐。国外市场的酸奶占液态奶的比重大约为40%,而我国则一直徘徊在15%左右。巨大的市场潜力、较高的毛利率,使饱受白奶价格战之苦的乳品企业纷纷加大了对酸奶的投资力度,“酸奶快跑”正成为乳业发展的亮点,2005年甚至被业界称为“酸奶年”。     

Effect of Purified Oat β-Glucan on Fermentation of Set-Style Yogurt Mix*

Effect of oat β-glucan on the fermentation of set-style yogurt was investigated by incorporating 0%, 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% of purified oat β-glucan into the yogurt mix. It was found that levels up to 0.3% resulted in yogurts with quality characteristics similar to the control yogurt. Higher levels of β-glucan however retarded the fermentation process with noticeable difference in the characteristics of the yogurt. Examination of the morphologies of yogurt with and without β-glucan revealed that β-glucan formed aggregates with casein micelle and did not form phase-separated domains. This research demonstrated that β-glucan could be added to yogurt up to 0.3%, which meets the nutrient guidelines, to have added nutritional benefits. Practical Application: Yogurt is known for its beneficial effects on human health and nutrition. Yogurt production and consumption is increasing in the United States every year. However, it is lacking in β-glucans, which are recognized for their nutritional importance as functional bioactive ingredients. The main objective was to develop and characterize low-fat yogurts with added β-glucan. This research demonstrated that β-glucan could be added to yogurt up to 0.3%, which meets the nutrient guidelines for added nutritional benefits, without affecting the characteristics of yogurt significantly. This study will benefit the dairy industry by generating new products offering healthy alternatives.     

The effect of starch based fat substitutes on the microstructure of set-style yogurt made from reconstituted skimmed milk powder

Seven different types of starch based fat substitutes were used for the production of set-style yogurt from reconstituted skimmed milk powder. The yogurt milks contained 14.0–15.8% total solids, 7.3–9.1% carbohydrates, 5.3–5.6% protein and 1.0–1.2% ash. The fat content of all the batches was 0.1% except the control (1.5%), which was made with anhydrous milk fat. Yogurts made with P-Fibre 150 C and 285 F contained 0.5 and 1.1% fibre respectively. Decrease in whey syneresis and increase in firmness in all the yogurts were observed during 20 days' storage at 5°C. Yogurt made with P-Fibre 150 C had the least amount of whey syneresis. Scanning electron microscopy and transmission electron microscopy revealed subtle differences in the microstructure of set-style yogurts due to the different starch based fat substitute used. 'Spikes' and 'hair' like structures were evident around the casein micelles in the milk base. They were lightly stained when compared with the caseins. Their detection in the yogurt was very difficult and only P-150 C and P-285 F substitutes were visualized whereas the others could not be detected even when their concentration was increased to 5%. Yogurt made with Lycadex® 100 was more porous and had slightly larger void spaces filled with milk serum. The use of a higher concentration (5%) of fat substitutes increased the firmness, but impaired the flavour and mouth feel of the yogurts.     

Conjugated Linoleic Acid and Fatty Acid Composition of Yogurt Produced from Milk of Cows Fed Soy Oil and Conjugated Linoleic Acid

ABSTRACT: Yogurt was processed from milk from Holstein cows whose diets were supplemented with soy oil (5%) and/or conjugated linoleic acids (CLA, 1%) to determine the effect of processing and dietary supplementation on CLA and fatty acid composition. Processing and storage for 7 d did not significantly affect CLA or fatty acid composition. CLA contents of milk and yogurt increased 2.8- and 2-fold by soy oil and CLA supplementation, respectively. Contents of saturated fatty acids decreased and trans -octadecenoic acids increased with the soy-oil-supplementation. The addition of CLA to soy-oil-supplemented diets did not significantly affect the CLA and fatty acid composition of the yogurt.     

Starch-lipid composites in plain set yogurt

Starch-lipid composites (SLC) were used to replace milk solids in yogurt mixes. The effects of the SLC on the yogurt fermentations and rheology were studied. The rate of fermentation was evaluated by the change of pH during the fermentation of yogurt. The syneresis of yogurt was observed over 3 weeks of storage. Small amplitude oscillatory shear flow measurements of the storage modulus, the loss modulus, and the loss tangent were obtained using a vane geometry. Yogurt mixes with milk solids partially replaced by SLC fermented at a similar rate than as with no milk solids replaced. Initial viscosity was higher for yogurt mixes with higher levels of SLC. The higher initial viscosity did not affect the gel structure. The addition of SLC above a level of 3% strengthened the gel and resulted in no syneresis for yogurt samples stored for 3 weeks at 4 °C.     

Immunological effects of yogurt addition to a re-nutrition diet in a malnutrition experimental model

The therapeutic and preventive effects of yogurt and lactic acid bacteria on diseases such as cancer, infection and gastrointestinal disorders are well ocumented. The aim of this research was to study the effects of different doses of yogurt addition after milk re-nutrition diet, on the recovery of the intestinal barrier and mucosal immune function. Experiments were performed on groups of mice, malnourished and re-nourished with milk during 7 d, and mice with diet supplemented with yogurt for 2, 5 and 7 consecutive d. Nutritional parameters such as weight gain, serum total protein, and the number of IgA, IgM and IgG B cells of the small intestine were determined. We also quantified intraepithelial leukocytes, mastocytes and goblet cells, and performed structural and ultrastructural studies on the small intestine. We observed that 5 d of yogurt feeding was the optimal dose for improving gut barrier function and mucosal immune system in a malnutrition model. This effect was not observed with milk re-nutrition. Although the results were better for 5 d of yogurt, addition for 7 d also showed beneficial effects. Yogurt feeding in our model did not impair any gut functions. These results suggest that yogurt addition after a re-nutrition diet gives better recovery of intestinal function than the re-nutrition diet usually recommended. Although these results were obtained in an animal model, they indicate that consumption of yogurt by malnourished children might accelerate the restoration of gut function.     

Soy Protein Fortification Affects Sensory, Chemical, and Microbiological Properties of Dairy Yogurts

ABSTRACT: Chemical, microbiological, and sensory properties for low fat yogurts fortified with 0,1, 2.5, or 5% soy protein concentrate were determined through 1 mo storage at 5 °C. Yogurts were adjusted to equivalent total solids with nonfat dried milk. Microbiological counts, fermentation time, and final developed acidity were not affected by soy protein. Instrumental viscosity and sensory thickness, soy aroma, and soy flavor increased with soy protein addition (P 0.05). Soy flavor and aroma did not increase with storage time. Yogurt with 5% soy protein was darker, more chalky, and less sweet compared to control yogurt or yogurts with lower concentrations of soy protein (P 0.05). Yogurts with 1 or 2.5% soy protein were most similar to control yogurt.     

Microstructure and rheology of yogurt made with cultures differing only in their ability to produce exopolysaccharides

Yogurt was made using an exopolysaccharide-producing strain of Streptococcus thermophilus and its genetic variant that only differed from the mother strain in its inability to produce exopolysaccharides. The microstructure was investigated using confocal scanning laser microscopy, allowing observation of fully hydrated yogurt and the distribution of exopolysaccharide within the protein network. Yogurt made with the exopolysaccharide-producing culture exhibited increased consistency coefficients, but lower flow behavior index, yield stress, viscoelastic moduli and phase angle values than did yogurt made with the culture unable to produce exopolysaccharide. The exopolysaccharides, when present, were found in pores in the gel network separate from the aggregated protein. These effects could be explained by the incompatibility of the exopolysaccharides with the protein aggregates in the milk. Stirring affected the yogurt made with exopolysaccharide differently from yogurt without exopolysaccharide, as it did not exhibit immediate syneresis, although the structural breakdown was increased. The shear-induced microstructure in a yogurt made with exopolysaccharide-producing culture was shown to consist of compartmentalized protein aggregates between channels containing exopolysaccharide, hindering syneresis as well as the buildup of structure after stirring.     

菊糖酸奶对小鼠免疫器官指数和血清免疫球蛋白的影响

以脾脏指数、胸腺指数、体质量及免疫球蛋白（immunoglobulin,Ig）IgG、IgA、IgM含量为评价指标,研究菊糖酸奶对小鼠免疫器官指数和血清免疫球蛋白的影响。结果表明：菊糖能够刺激酸奶中乳酸菌的增加。与普通酸奶相比,菊糖酸奶能够更好地提高小鼠免疫功能,经相关性分析发现IgG、IgA与酸奶中乳酸菌的含量显著相关。由此可见,菊糖刺激了酸奶中乳酸菌的增加,从而增强了酸奶对机体免疫功能的影响。在菊糖添加量为50 g/L时,菊糖酸奶对小鼠的免疫增强效果最好。     

Scientific and Technical Aspects of Yogurt Aroma and Taste: A Review

Abstract: Yogurt is a basic dairy product that has been consumed for centuries as a part of the diet, even when its beneficial effects were neither fully known nor scientifically proven. With time, yogurt has been continuously modified to obtain a product with better appeal and nutritional effects. The flavor components of yogurt are affected because of these modifications. The present review article is focused on the influence of the different parameters and modifications on aroma and taste components of yogurt. Extensive work has been done to explore the effect of chemical components as well as the microbial, processing, and storage aspects. The popularity of yogurt as a food component depends mainly on its sensory characteristics, of which aroma and taste are most important. This review also outlines the effects of the different modifications attempted in the composition of yogurt.     

Effect of Fortification with Various Types of Milk Proteins on the Rheological Properties and Permeability of Nonfat Set Yogurt

ABSTRACT: Yogurt base was prepared from reconstituted skim milk powder (SMP) with 2.5% protein and fortified with additional 1% protein (wt/wt) from 4 different milk protein sources: SMP, milk protein isolate (MPI), micellar casein (MC), and sodium caseinate (NaCN). Heat‐treated yogurt mixes were fermented at 40 °C with a commercial yogurt culture until pH 4.6. During fermentation pH was monitored, and storage modulus (G′) and loss tangent (LT) were measured using dynamic oscillatory rheology. Yield stress (σ_yield) and permeability of gels were analyzed at pH 4.6. Addition of NaCN significantly reduced buffering capacity of yogurt mix by apparently solubilizing part of the indigenous colloidal calcium phosphate (CCP) in reconstituted SMP. Use of different types of milk protein did not affect pH development except for MC, which had the slowest fermentation due to its very high buffering. NaCN‐fortified yogurt had the highest G′ and σ_yield values at pH 4.6, as well as maximum LT values. Partial removal of CCP by NaCN before fermentation may have increased rearrangements in yogurt gel. Soluble casein molecules in NaCN‐fortified milks may have helped to increase G′ and LT values of yogurt gels by increasing the number of cross‐links between strands. Use of MC increased the CCP content but resulted in low G′ and σ_yield at pH 4.6, high LT and high permeability. The G′ value at pH 4.6 of yogurts increased in the order: SMP = MC < MPI < NaCN. Type of milk protein used to standardize the protein content had a significant impact on physical properties of yogurt. Practical Application: In yogurt processing, it is common to add additional milk solids to improve viscosity and textural attributes. There are many different types of milk protein powders that could potentially be used for fortification purposes. This study suggests that the type of milk protein used for fortification impacts yogurt properties and sodium caseinate gave the best textural results.     

益生菌制剂及其发酵性乳制品

综述了益生菌的概念和益生菌菌株的选择标准、国外益生菌产品的发展状况、益生菌作为新型酸奶发酵剂的使用情况，以及益生酸奶的生产与消费情况。     

酸奶产品健康相关信息对各类消费者选购意图的影响

目的:研究不同消费群体对酸奶的健康相关因素的关注程度,以及对酸奶消费的影响。方法:以随机访问的方式对北京市615名消费者进行问卷调查,数据使用SPSS 18.0进行分析。结果:女性、教育程度较高、接受过健康培训和关注营养信息者对酸奶的健康益处了解较全面。女性、较年轻、有过健康培训、关注健康信息的人群饮用酸奶的频率较高。年龄、人均月收入、教育程度、健康培训与酸奶风味和口感的重视程度呈显著负相关,而与营养价值和保健价值的重视程度呈显著正相关。女性、月收入高、教育程度高、接受过健康培训、关注健康信息的人群倾向于选择带有营养声称的酸奶。结论:不同消费群体对酸奶的消费选择特点有显著差异。     

Improved media for differentiation of rods and cocci in yogurt

Selected yogurt starters and commercial samples grew on Elliker's lactic agar supplemented with .1% Tween 80 and 50 micrograms/ml of 2,3,5-triphenyltetrazolium chloride to produce small, red Streptococcus thermophilus colonies and larger, white Lactobacillus bulgaricus colonies. The distinction was somewhat strain dependent but was satisfactory in most cases. Addition of 7% skim milk (11% solids) to lactic agar in place of 2,3,5-triphenyltetrazolium chloride allowed good rod-coccus differentiation, regardless of strain or yogurt brand. On this medium, called yogurt lactic agar, L. bulgaricus appeared as large white colonies surrounded by a cloudy zone and S. thermophilus as smaller white colonies devoid of a surrounding halo. Casein precipitation was responsible for the halo effect around the more acidogenic L. bulgaricus colonies. Yogurt lactic agar compared favorably with S. thermophilus and Lactobacillus agar media for the recovery of S. thermophilus and L. bulgaricus in single and mixed cultures.     

Effect of Inoculation Level of Lactobacillus rhamnosus and Yogurt Cultures on Conjugated Linoleic Acid Content and Quality Attributes of Fermented Milk Products

ABSTRACT:  The effect of inoculation concentration of Lactobacillus rhamnosus and yogurt cultures and storage time on conjugated linoleic acid (CLA) content and quality attributes of fermented milk products was determined. Yogurt culture ( Lactobacillus bulgaricus and Streptococcus thermophilus, 1:1 ratio, YC ) , L. rhamnosus (LB), and LB co-cultured with yogurt culture, were inoculated at 10⁶, 10⁷, 10⁸ CFU/mL into a milk with hydrolyzed soy oil as the lipid source. CLA content, microbial counts, acidity, texture, and volatile flavor profile of the fermented milk products were stable during storage at 4 °C for 14 d. Total CLA contents ranged from 0.51 to 1.00 mg CLA/g lipid following 14 d of storage. Inoculation level of L. rhamnosus and yogurt cultures had no significant effect on CLA content and texture, but affected acidity and the volatile flavor profile of the fermented milk products. The fermented milk products produced by L. rhamnosus co-cultured with yogurt culture with 10⁷ CFU/mL total inoculation level resulted in a high CLA content and desirable quality characteristics. This research demonstrated that the optimal inoculation concentration and the combination of L. rhamnosus and yogurt cultures were important factors to produce fermented milk products with CLA content and acceptable quality attributes.