Functionality of enterococci in meat products

The presence of enterococci in meat fermentation is a constant as reported in the literature. Despite the concern about pathogenicity of enterococci, recent studies point out that food and meat enterococci, especially Enterococcus faecium have a much lower pathogenicity potential than clinical strains. Enterococci possess a competitive advantage over other microbiota in meat fermentations, and many enterococci isolated from sausages have the ability to produce enterocins harbouring antimicrobial activity against pathogens and spoilage microorganisms of meat concern. The application of enterocins producing enterococci or their purified metabolites, as extra hurdles for preservation in sausage fermentation and in sliced-vacuum packed cooked meat products can be beneficial, preventing the outgrowth of Listeria monocytogenes and slime-producing lactic acid bacteria. Enterocins and bacteriocinogenic enterococci hold considerable promise as alternatives to traditional chemical preservatives and they could be exploited for the control of emergent pathogens in meat products. Their inhibitory effect can be increased when used in conjunction with particular physical and chemical processes, but current regulation is hampering the application of purified bacteriocins.     

Prevalence of enterococci in frozen dairy products and their pathogenicity

Enterococci were present in all the samples of frozen dairy products examined in the present study. The total bacterial counts as well as enterococcal counts were generally very high in Kulfi (a frozen product similar to ice cream) and Kulfi mix. Among 161 enterococcal isolates recovered, the predominant type was Streptococcus faecalis var. faecalis, the majority of isolates coming from Kulfi and Kulfi mix samples. Although 58 cultures produced deoxyribonuclease, only two of them exhibited thermonuclease (TNase) production. Hyaluronidase activity was shown by three strains. However, 31 strains were alpha haemolytic, while five showed beta haemolysis on rabbit blood agar. Out of these haemolytic strains tested, 21 produced lethal toxicity in mice and 20 strains showed culture virulence, postmortem studies revealed congestion of heart, liver, kidney and spleen. The two TNase positive strains of Streptococcus faecium produced fluid accumulation in ligated ileal loops of rabbits and distension in the gastrointestinal tracts of infant mice.     

Functionality of strawberry powder on frozen dairy desserts

This study investigated the potential use of freeze‐dried strawberry powder as a stabilizer in frozen dairy desserts. Five different dessert mixes were developed that contained 0%, 2.5%, 3%, 3.5%, and 4% strawberry powder. An additional dessert using strawberry extract was prepared to differentiate the effects of dietary fiber from the effect of polyphenols on sample properties. The rheological and physical characteristics of dessert mixes, fresh dessert, and stored dessert were studied. The addition of strawberry powder to dairy desserts caused an increase in the mix viscosity and a decrease in hardness and meltdown values. Complete avoidance of meltdown was achieved with the addition of 3% or greater amount of strawberry powder. The viscosity of mixes was enhanced due to the increase of total solids in the serum phase and the formation of hydrated and gel‐like networks in the presence of cellulosic material, pectin, and calcium. The increase in viscosity and unfrozen water with the addition of strawberry powder also caused a reduction in ice crystallization, which resulted in softer and more stable desserts over time.     

大豆分级蛋白的功能性质评价

利用″碱溶酸沉″方法,得到富含大豆球蛋白的大豆分级蛋白产品Ⅰ和富含β-伴球蛋白的大豆分级蛋白产品Ⅱ。经与市售的大豆分离蛋白产品进行功能性质的比较,大豆分级蛋白的某些功能性质,如胶凝性、乳化性、发泡性得到了改善和提高。      

Calcium in dairy products

Increasing attention has been given to the nutritional role of calcium because many Americans do not consume their Recommended Dietary Allowance of this nutrient and because calcium deficiency may lead to the development of osteoporosis or other disorders. Calcium is absorbed in the intestines with the aid of a vitamin D metabolite and is used in the body for many essential functions. There are several ways to obtain calcium in the diet, but the best sources are milk and other dairy products because of their low cost and high bioavailability of this mineral. Some manufacturers have responded to the concern over lack of calcium in the diet by increasing its levels in milk. The amount of calcium in cheese and yogurt also can be elevated.     

光谱技术在乳及乳制品研究中的应用进展

文章阐述了光谱技术在乳及乳制品掺假和掺伪检测、营养成分检测、抗生素检测、微生物污染检测,乳及乳制品种类的鉴定等方面的应用。综述了近红外光谱、拉曼光谱、高光谱成像技术在乳及乳制品品质检测和安全评定上的重要应用和研究进展,指出多种技术联合应用是未来研究的趋势。     

Mycotoxins in dairy products

Certain fungi produce chemical substances that cause toxic symptoms when food containing them is ingested by man or animals. These compounds are referred to as mycotoxins. Mycotoxins may contaminate dairy products by moulds growing on them, or by the carry-over of mycotoxins occurring in animal feedstuffs ingested by dairy cattle. An example of the first mentioned category is sterigmatocystin, a carcinogenic mycotoxin sometimes occurring on hard cheese. An example of the second category is aflatoxin M₁, a compound strongly suspected to be carcinogenic, which often occurs in milk. Due to the fact that processing of milk does not decrease the aflatoxin M₁ content, aflatoxin M₁ occurs in various dairy products. Sensitive methods of analysis for the determination of mycotoxins in dairy products have been developed in the last 10 years, most of them are based on TLC- or HPLC-separation procedures, followed by fluorimetric measurement.The most fundamental way to tackle the problem of mycotoxin contamination of dairy products is to prevent fungal growth on the dairy products or, in the case of carry-over of mycotoxins, in the crop before, during and after harvest. If measures to prevent fungal growth and mycotoxins production are not taken or fail, one can sometimes resort to physical or chemical methods to eliminate mycotoxins.     

功能性乳制品

<正> 随着生活水平的提高,人们的保健意识愈来愈强,具有功能性的乳制品正逐渐成为崇尚健康的消费者的选择。来自芬兰的维利奥(Valio)有限公司在功能性乳制品研发方面取得不断的创新。     

Functionality of oilseed protein products: A review

Oilseed proteins and modified or processed oilseed proteins can be incorporated into foods to impart nutritive value and functional properties. Processing of vegetable protein involves physico-chemical and thermal treatments, affecting the nutritional value of the final products, and also the functional properties. Conversely, functional properties (solubility, water and oil retention capacity, foaming capacity and stability, emulsion capacity and stability, viscosity, gelation) influence protein behaviour during processing and storage. These properties can be modified by chemical and enzymatic treatment. Data corresponding to diverse oilseeds and from different deffating and extraction processes have been complied and grouped according to the protein content into meals, concentrates, and isolates. Three groups of technological properties of interest for the formulation of proteinic food products from oilseeds were considered: (i) properties related to hydration mechanisms, (ii) properties related to protein structure and rheology and (iii) properties related to protein surface.     

Bioactive peptides in dairy products

Bioactive peptides are hydrolysates with specific amino acid sequences that exert a positive physiological influence on the body. They are inert within the native protein, but once cleaved from the native protein by microbial or added enzymes and/or gastrointestinal enzymes during the digestive process, they apply their beneficial traits. Dairy products, particularly fermented products, are potential sources of bioactive peptides: several of them possess extra‐nutritional physiological functions that qualify them to be classified under the ‘Functional Foods’ label. Biological peptides in milk, the methods of their generation and their prevalence in dairy products are reviewed along with the reported health benefits and safety aspects.     

Sphingoid bases in dairy products

Sphingolipids have recently been taken more into consideration because of their possible role in health care.The aim of this study was to determine the concentration of free and total sphingosine and sphinganine in dairy products, a food group that has been given a role in the prevention of colon cancer and other tumours. Sphingolipids were extracted using chloroform and methanol, and following base and acid hydrolysis, the free and total sphingosine and sphinganine were quantified using high-performance liquid chromatography. The highest concentrations of free and total sphingosine and sphinganine were found in sour cream. In most of the analyzed dairy products, the concentrations of free sphingoid bases were lower than that of cow’s milk, while the concentrations of the total sphingoid bases were equal to or higher than that of cow’s milk.     

Biogenic amines in dairy products

Biogenic amines (BA) are organic, basic, nitrogenous compounds with biological activity, mainly formed by the decarboxylation of amino acids. BA are present in a wide range of foods, including dairy products, and can accumulate in high concentrations. In some cheeses more than 1000 mg of BA have been detected per kilogram of cheese. The consumption of food containing large amounts of these amines can have toxicological consequences. Although there is no specific legislation regarding the BA content in dairy products, it is generally assumed that they should not be allowed to accumulate. Greater knowledge of the factors involved in the synthesis and accumulation of BA should lead to a reduction in their incidence in foods. This article focuses on the factors that affect BA production, in particular environmental conditions, the microorganisms that produce them, the genetic organization and regulation of the biosynthetic pathways involved, and the available methods for detecting the presence of BA or BA-producing microorganisms in dairy products.     

Enumeration of bifidobacteria in dairy products

There is much interest in the potential role of bifidobacteria as dietary inclusions, but their isolation from dairy products, and subsequent identification, can cause problems. A range of selective and non-selective media were examined, and modified Rogosa agar was found to give the best recovery from yogurt-like products. A morphological examination of typical isolates suggested that only bifidobacteria had grown on the medium, but confirmation by means of biochemical tests proved inconclusive, and it seems that the genus/species definition merits further attention.     

乳制品中纳他霉素的测定

建立了测定乳制品中纳他霉素含量的高效液相色谱法。样品用甲醇萃取后进样,采用Thermo ODS-2250min&#215;4.6mm色谱柱分离,流动相为乙酸铵与氯化铵的缓冲液：乙腈=4：1（体积比）,加入5InL四氢呋喃（每升）,紫外检测;A-R303nm,RSD为0．56％-0．82％（n=5）,标准曲线r=0．9998,平均回收率分别为98．2％,最低检出限为0．05mg／L。本法具有操作简单、灵敏度高和准确性好等优点。     

卵磷脂在乳制品中的应用

<正> 卵磷脂萃取自大豆,是一种天然的乳化剂,可广泛应用于不同的食品中。在乳制品中,卵磷脂已普遍在奶粉、干酪、冰淇淋和奶油制品等产品中使用,本文将详细探讨这些领域的应用情况。 速溶奶粉 奶粉通常采用附聚处理以形成粗糙的颗粒,便于冲调饮用。然而,由于奶粉颗粒大多被脂肪覆盖,形成对水的排斥性,故此,单独采用附聚处理,不能     

亲水性胶体在乳制品工业中的应用

<正> 亲水性胶体是指水溶性多糖,其作用是使多糖分散体系具有黏度和形成凝胶的能力。根据原料来源,亲水性胶体可分为:生物胶(黄原胶、葡聚糖、结冷胶)、植物胶(刺槐豆胶、瓜尔豆胶)、植物渗出液(阿拉伯胶、黄耆胶)、海藻胶(卡拉胶、琼胶)、纤维素及衍生物(纤维素、羧甲基纤维素(钠))、淀粉及其衍生物、动物胶(明胶)、果胶。 在乳制品工业中被广泛应用的亲水性胶体主要有刺槐豆胶、瓜尔豆胶、果胶和卡拉胶。主要作用是保护体系中的蛋白质以耐受加工中