Evaluation of trichloromethane formation from chlorine‐based cleaning and disinfection agents in cow’s milk

The development of trichloromethane (TCM) in milk can result from the use of chlorine‐based detergent solutions during the milk production process. Different factors affecting the development of TCM in milk were investigated. Gas chromatography with electron capture detector was the method of analysis. Combining milks of different TCM levels resulted in milk TCM levels similar to that calculated mathematically. Increased chlorine concentration in the detergent and reduced rinse water volume resulted in increased TCM concentrations (P < 0.05) in milk, while the addition of chlorine to the rinse water also increased (P < 0.001) milk TCM.     

Does the addition of caseinophosphopeptides or milk improve zinc in vitro bioavailability in fruit beverages?

The influence of caseinophosphopeptides (CPPs) added to fruit beverage versus milk based fruit beverage upon zinc retention, transport, and uptake, as well as the influence of Fe supplementation, were studied using a combined simulated gastrointestinal digestion/Caco-2 cell system.Zinc retention, transport, and uptake of milk based fruit beverage was 4- to 5-fold greater than that of fruit beverages with or without CPPs – no statistically significant differences being observed in relation to the presence or absence of CPPs. Possibly, a slow release of CPPs throughout the digestive tract, as can be expected to take place during the digestion of casein, has a more beneficial effect than the addition of preformed CPPs upon Zn availability.A significantly negative Fe × Zn interaction in relation to Zn retention and uptake was observed in fruit beverages. This should be taken into account in the formulation of such beverages, where the supplementing of both of these mineral elements is common practice.     

Kinetic and thermodynamic study of thermal inactivation of the antimicrobial peptide P34 in milk

The knowledge on thermal inactivation of biopreservatives in a food matrix is essential to allow their proper utilisation in food industry, enabling the reduction of heating times and optimisation of heating temperatures. In this work, thermal inactivation of the antimicrobial peptide P34 in skimmed and fat milk was kinetically investigated within the temperature range of 90–120 °C. The inactivation kinetic follows a first-order reaction with k-values between 0.071 and 0.007 min⁻¹ in skimmed milk, and 0.1346 and 0.0119 min⁻¹ in fat milk. At high temperatures, peptide P34 was less resistant in fat milk, with a significant decrease in residual activity as compared with skimmed milk. At temperatures below 110 °C, the fat globules seem to have protective effect to the peptide P34. Results suggest that peptide P34 is heat stable in milk with activation energy of 90 kJ mol⁻¹ in skimmed milk and 136 kJ mol⁻¹ in fat milk.     

Antioxidant effect derived from bioaccessible fractions of fruit beverages against H2O2-induced oxidative stress in Caco-2 cells

This work evaluates the effect of bioaccessible fractions from fruit beverages against oxidative stress (OS) in Caco-2 cells. A fruit beverage (grape + orange + apricot) (with/without milk and/or iron/zinc) was subjected to in vitro gastrointestinal digestion, and bioaccessible fractions were incubated with Caco-2 cell cultures. Following preincubation, OS was induced with 5 mM H₂O₂. Intracellular reactive oxygen species (ROS), mitochondrial potential (Δψ_m), mitochondrial metabolism (MTT test), intracellular reduced glutathione (GSH) and superoxide dismutase activity (SOD) were measured. The data evidenced viable cultures with increased mitochondrial metabolism and GSH-Rd activities, without alteration in SOD activity. Accordingly, more preserved mitochondrial integrity was also evidenced, allowing the action of antioxidant systems in preincubated cultures. Based on these data, we can conclude that a cytoprotective effect is derived from bioaccessible fractions of fruit beverages, though this effect failed to prevent intracellular ROS accumulation in Caco-2 cell cultures exposed to 5 mM H₂O₂.     

Effect of refrigerated storage time on the viability of probiotic bacteria in fermented probiotic milk drinks

The viability of Lactobacillus acidophilus and Bifidobacterium lactis in fermented milks A, B and AB, containing respectively these strains separately and mixed, was studied over 21 days of storage at 5°C. Samples were analysed for titratable acidity and viable cell counts of probiotics. Milks A and AB showed post-acidification mainly due to the β-galactosidase activity of L. acidophilus . Generally, the viability of the probiotics decreased during storage, whereas, in some cases, the proteoletic activity of L. acidophilus resulted in a higher survival rate of the probiotics even with the adverse effects of low temperature and organic acids.     

Bioactive compound levels and sensory quality of partially skimmed organic yoghurts: Effects of the milk treatment,production season and starter culture*

The aim of the study was to assess the physicochemical properties, texture, colour and sensory quality of organic yoghurts with regard to the milk treatment (raw milk obtained directly from organic farms, partially skimmed and heat‐treated in the laboratory vs organic milk purchased in the shop that was pasteurised in a dairy), production season and starter culture. The yoghurts produced on the basis of bulk milk obtained from farms during the spring/summer season proved to be of greater nutritional value and had higher content of bioactive whey proteins, except for β‐lactoglobulin, and lipophilic vitamins than retail milk.     

金黄色葡萄球菌在生乳与灭菌乳中生长状况分析

目的 了解并比较金黄色葡萄球菌(S.aureus)在生乳与灭菌乳中的生长状况.方法 采用GB/T4789.37-2008<食品微生物学检验金黄色葡萄球菌检验>,测定不同温度下金黄色葡萄球菌在生乳和灭菌乳中的生长情况,利用MicroFit 1.0软件对所测数据进行分析,利用SPSS统计软件对该菌在生乳与灭菌乳中生长参数进行统计分析.结果 金黄色葡萄球菌在生乳中的最大生长速率明显低于在灭菌乳中的最大生长速率,二者的迟滞期、代时无明显差异.结论 金黄色葡萄球菌在生乳与灭菌乳中的生长情况差异显著.有统计学意义(P<0.05).     

Influence of total solids contents of milk whey on the acidifying profile and viability of various lactic acid bacteria

The main objectives of the present study were (a) to study the effects of the different combinations of Lactobacillus delbrueckii subsp. bulgaricus (Lb), Lactobacillus acidophilus (La), Lactobacillus rhamnosus (Lr), and Bifidobacterium animalis subsp. lactis (Bl) in co-culture with Streptococcus thermophilus (St) on the rate of acid development in milk and milk-whey mixture, and (b) the effect of the level of the total solids of the different bases on the acidification profile and viability of potential health-promoting micro-organisms. The co-culture of St-Lr showed the lowest values V_max in all bases; while the co-culture St-Bl had high t_Vmax in milk and whey bases (12 and 10 g/100 g, respectively). Co-cultures St-La and St-Lb reached V_max at pH 5.5, while St-Lr and St-Bl at pH 5.91. Fermentation time to reach pH 4.5 was longer when St-Lr co-culture was used, while St-Lb had the lowest value. All the products had slight development of acid during the storage period, and lowest values were observed when the St-Bl co-culture was employed. Lb, Bl and St cultures had high counts at pH 4.5 in the three bases. The total solids affected the viability of Lb and La. The technological interest of these combinations is discussed in this article.     

Studies on the development of beverages using fruit juice/pulp, separated milk and reconstituted skim milk

Studies were carried out on the development of beverages using fruit juice/pulp, separated milk and reconstituted skim milk. Beverages were prepared by blending juice/pulp from apples, bananas, guavas, litchis and mangos at four different concentrations (100, 200, 300 and 400 g/L) with separated and reconstituted skim milk. Organoleptic evaluation of the beverages showed that apple juice and guava pulp could be blended at up to 300 and 100 g/L in milk products, respectively. Banana and mango pulp could also successfully be used at up to 200 g/L in separated milk and reconstituted skim milk. Litchi juice could be blended up to 300 g/L in separated milk and 200 g/L in reconstituted skim milk.     

几种糖醇类甜味剂在调配型酸乳饮料中的应用研究

对几种糖醇类甜味剂在调配型酸乳饮料中的应用与蔗糖进行了对比研究，发现结晶麦芽糖醇、液体麦芽糖醇均可作为良好的蔗糖替代品生产无糖调配型酸乳饮料。     

果醋发酵液残留乙醇含量的快速检测

在康维皿比色法的基础上,建立了一种快速测定果醋发酵液残留乙醇的新方法。结果表明:采用康维皿作为反应容器,乙醇反应体系在580nm处具有最大吸收峰。果醋中的乙醇浓度在0.5%～10%（v/v）之间呈良好线性,回归方程为Y=0.07389X-0.00886,相关系数R2=0.9995。该方法具有取样量少、快速、准确、无需复杂仪器等优点,不仅适于测定果酒或果醋终产品的乙醇含量,也便于跟踪果酒或果醋生产过程的乙醇含量动态变化,具有较好的应用推广价值。      

Probiotic viability and physico-chemical and sensory properties of plain and stirred fruit yogurts made from goat's milk

Probiotic plain and stirred fruit yogurts were made from goat's milk using bacterial cultures comprising, Lactobacillus acidophilus LA-5, Bifidobacterium animalis subsp. lactis BB-12 and Propionibacterium jensenii 702. The products were stored at 4°C for 4weeks, during which time the viability of the yogurt starter culture and probiotic bacteria was analysed weekly. P. jensenii 702 demonstrated the highest viability (10(8)cfu/g) in all types of yogurt throughout the storage period, while the viability of the bifidobacteria (～10(7)cfu/g) also remained above the minimum therapeutic level. The viability of L. acidophilus LA-5 fell below 10(6)cfu/g in yogurts, however, the addition of fruit juice appeared to support the viability of lactobacilli, with higher microorganism numbers observed in fruit yogurts than in plain yogurt throughout the shelf life. Addition of fruit juice significantly increased the syneresis, and decreased viscosity and water holding capacity of yogurts (p<0.05), and also enhanced their sensory acceptability.     

Recent developments in antibody-based analytical methods for the differentiation of milk from different species

The antibody-based analytical methods for the detection of milk from different species that have been developed in recent years are, for the most part, various enzyme-linked immunosorbent assay (ELISA) configurations. Polyclonal and, more recently, monoclonal antibodies against total or individual caseins, whey proteins and synthetic peptides corresponding to milk proteins sequences have been used. The assays have been successfully applied to the detection of substitution of ovine or caprine milk by bovine milk and of ovine milk by caprine milk in raw and heat-treated milks and cheeses.     

Identification of micrococcaceae isolated from goat''s milk and cheese in the Poitou-Charentes region

One hundred and ninety strains of coagulase-negative staphylococci were isolated from goat's milk, whey and cheese at various stages of manufacture.

Sixteen different coagulase negative Staphylococci (CNS) species were recovered, 3 of which were predominant: Staphylococcus simulans, Staphylococcus epidermidis and Staphylococcus xylosus.

The prevalent species were recovered at least at two different stages of cheese manufacturing, suggesting a better adaptation to the environment. After 15 days of ripening, the cheeses showed lower counts of Micrococcaceae.     

Milking and milk processing: traditional technologies in the yak farming system of the Qinghai-Tibetan Plateau, China

Yak milk and its products are widely consumed by local herders and are regarded as the resources of economic income by the households on the Qinghai-Tibetan Plateau. Yak raisers have developed their own milking skills and milk-processing technologies through a long history of yak keeping. All of these traditional skills and technologies have their own characteristics. In this paper, the methods and procedures of milking and milk processing in yak farming systems are reviewed.     

Concentration of furfuryl alcohol in fluid milk,dried dairy ingredients,and cultured dairy products

Maillard reactions occur in dairy products during heat treatment. Furfuryl alcohol (FA) may be found in dairy products as a result of Maillard reactions. The recent posting in California Proposition 65 indicates that FA may be carcinogenic, and for this reason it is crucial to accurately measure FA concentrations in dairy products. The objective of this study was to identify an extraction and quantitation method for FA from dairy products and to determine FA concentrations in milk, dairy powders, and cultured dairy products. Solvent-assisted flavor extraction, solid-phase microextraction, stir bar sorptive extraction with gas chromatography-mass spectrometry and triple quadrupole mass spectrometry were compared for recovery of FA. Internal standards for the quantitation of FA (2-methyl-3-heptanone, furfuryl-d₅ alcohol, 2,5-dimethylphenol, 5-methyl-2-furfuryl alcohol, and 5-methyl furfural) were also compared. Subsequently, fluid milk [high temperature, short time (HTST) and ultrapasteurized], whey protein isolates (3 mo–4 yr), whey protein concentrates (3 mo–4 yr), whole milk powders (1 yr), high and low heat skim milk powders (SMP; 0–8 yr), milk protein isolates (3 mo–3 yr), milk protein concentrates (3 mo–3 yr), Cheddar cheese (mild, medium, sharp, and extra sharp), mozzarella cheese (whole and part skim), cottage cheese (nonfat, low fat, and full fat), sour cream (nonfat, low fat, and full fat), traditional yogurt (nonfat, low fat, and full fat), and Greek-style yogurt (nonfat; n = 139 products total) were evaluated. Furfuryl alcohol was extracted from products by headspace solid-phase microextraction followed by gas chromatography-triple quadrupole mass spectrometry using a ZB-5ms column (30 m × 0.25 mm × 0.25 µm; Phenomenex Inc., Torrance, CA). Furfuryl-d₅ alcohol was used as an internal standard. Each food was extracted in triplicate. Ultrapasteurized milks had higher levels of FA than HTST milks (122.3 vs. 7.350 µg/kg). Furfuryl alcohol concentrations ranged from 0.634 to 26.55 µg/kg in whey protein isolates, 2.251 to 56.19 µg/kg in whey protein concentrates, 11.99 to 121.9 µg/kg in milk protein isolates, and 8.312 to 49.71 µg/kg in milk protein concentrates, and concentrations increased with powder storage. High heat SMP had higher concentrations of FA than low heat SMP (11.8 vs. 1.36 µg/kg) and concentrations increased with storage time. Concentrations of FA in Cheddar and mozzarella cheese ranged from 2.361 to 110.5 µg/kg and were higher than FA concentrations in cottage cheese or sour cream (0.049–1.017 µg/kg). These results suggest that FA is present at higher levels in dairy products that have been subjected to higher temperatures or have been stored longer. Sour cream and cottage cheese had lower levels of FA. Compared with other studies on food products with reported levels of FA, such as coffee (200–400 µg/g), dairy products have very low levels of FA.     

Evaluation of different methods for the production of juice concentrates and fruit powders from cactus pear

The present work aimed both at improvement and extension of a previously developed process for the production of cactus pear juice. The total yield was increased by 10% through processing whole instead of peeled fruits and by further optimisation of pulp enzymation. As an alternative to HTST pasteurisation, cross-flow microfiltration was applied for non-thermal cactus pear juice preservation. Juice concentrates and fruit powders were produced by rotary evaporation and freeze drying at laboratory scale and compared to products obtained at pilot plant-scale applying a three-stage column evaporator and spray drying, respectively. To monitor process-related quality changes, the resulting products were characterised in terms of colour and selected quality parameters. For both juice concentrates and fruit powders, initial colour characteristics were retained. In addition to betanin isomerisation, C₁₁-epimerisation of proline-betaxanthin was demonstrated to be a valuable indicator of the respective heat treatment applied. Whereas no adverse reactions were observed during juice production, non-enzymatic browning and HMF formation were found after concentration at pilot plant-scale and freeze drying, respectively.

Industrial relevance

Although cactus pear meets all requirements for food colouring purposes, no attempt has been made so far to exploit this potential. The feasibility of processing cactus pear juice into concentrates and fruit powders was demonstrated in this study. In contrast to single-strength juice, concentrates and powders are easier to handle during transportation and storage and also open further fields of application that may promote cactus pear fruit processing at industrial scale in the future.     

免疫亲和柱-高效液相色谱法检测乳制品中氯霉素

建立免疫亲和柱富集净化、高效液相色谱-紫外法快速测定牛奶和奶粉中氯霉素残留物。样品用乙酸乙酯提取,经免疫亲和色谱柱纯化,应用液相色谱-紫外法检测。结果表明,牛奶和奶粉添加氯霉素,回收率为79.6%~108.6%,变异系数小于10%;方法检测灵敏度0.1μg/L。该方法能够特异性的纯化牛奶和奶粉样品中的氯霉素,免疫亲和柱(IAC)净化是一种简单,快速,准确的方法。     

Trace element levels in raw milk from northern and southern regions of Croatia

A total of 157 raw milk samples were collected from tankers arriving at processing facilities from rural areas in northern and southern regions of Croatia during 2009 and 2010. Concentrations of As, Cd, Cu, Hg and Pb in the samples were analysed by graphite furnace-atomic absorption spectroscopy. Mean Pb concentrations in northern and southern regions were 58.7 and 36.2 μg l⁻¹, respectively, and both exceeded the maximum recommended level. Arsenic concentrations ranged from 1 to 283 μg l⁻¹ in the southern and to 1019 μg l⁻¹ in the northern regions. Mean Cd and Hg levels were: 1.76 and 1.59 in the northern and 3.4 and 7.1 μg l⁻¹ in the southern region. Significantly higher Cd and Hg levels were observed in the southern than in the northern region (p < 0.001, both). Similar mean Cu levels were found in both regions: 931.9 in the north and 848.4 μg l⁻¹ in the south. The results indicate that particular attention should be paid to Pb residues. In future studies, a greater number of milk samples and grass samples from pastures from different regions of Croatia should be controlled to confirm the absence of possible toxicological risks.