Short communication: Aflatoxin M1 in dairy products sold in Şanlıurfa,Turkey

The aim of this study was to detect the presence of aflatoxin M₁ (AFM1) in samples of raw milk (n = 38), UHT milk (n = 12), white pickled cheese (n = 50), and yogurt (n = 50) collected from the ?anl?urfa city markets and locally produced dairy products by ELISA. The mean contamination rates were 56.74 ± 40.32, 43.1 ± 23.19, 103.2 ± 29.13, and 55.28 ± 12.68 ng/kg, respectively, for raw milk, UHT milk, white pickled cheese, and yogurt. According to the data, 21 (55%) raw milk, 3 (25%) UHT milk, 10 (20%) white pickled cheese, and 10 (20%) yogurt samples were contaminated with AFM1 over the acceptable levels (≥50 ng/kg), ranging from 0.82 to 130.89 ng/kg. None of the white pickled cheese samples contained AFM1 levels above the Turkish legal limit (250 ng/kg). Consequently, the AFM1 contamination levels determined in this study in white pickled cheese were not considered to pose a serious public health hazard. However, the AFM1 levels in raw and UHT milk and yogurt samples indicate an increased human health risk in Turkey related to high aflatoxin levels. Therefore, milk and dairy products have to be monitored by the Turkish public health authorities continuously to detect AFM1 contamination.     

The occurrence of Listeria species in milk and dairy products: a national survey in England and Wales

A total of 4172 samples of milk, cheese and other dairy products were examined over a 1-year period for the presence of Listeria species. Strains of Listeria were found most frequently in soft, ripened cows milk cheese; 63 out of 769 (8.2%) samples contained Listeria monocytogenes, 25 samples contained species other than L. monocytogenes, and 18 samples contained both L. monocytogenes and other Listeria spp. Eleven samples of pasteurized cows milk (1.1%) from four dairies contained L. monocytogenes, and other Listeria spp. were isolated from a further five samples. Goats and ewes milk and their products, yogurt, cream and ice cream also occasionally contained Listeria spp. Levels of Listeria were usually low, but 20 samples of cheese contained more than 1000 cfu/g. Most strains of L. monocytogenes belonged to serotype 1/2 (58%) or serotype 4b (33%).     

Determination of bovine lactoferrin in lactoferrin-supplemented dairy products and raw milk by an automated latex assay

Latex immune agglutination method with a multipurpose auto-analyser (the automated latex assay) was validated for determination of bovine lactoferrin (BLF) in various dairy products. Reproducibility-within-laboratory (intermediate precision) due to day for infant formula, UHT milk and yogurt supplemented with BLF at 50 mg/100 g for infant formula and UHT milk, and at 100 mg/100 g for yogurt were 1.62 to 3.10 mg/100 g. Reproducibility-within-laboratory due to analysis (morning, noon, and evening) for raw milk was 1.59 mg/100 g. Trueness, accuracy in determining known amounts added for BLF-supplemented dairy products was -4.7 to -2.0 mg/100 g. BLF concentration in raw milks was 20.3 to 21.8 mg/100 g. Although interference by the matrixes took place in infant formula and raw milk, BLF assays were accurately carried out by 2000-fold dilution or standard-addition method. Automated latex assay for BLF is simple, rapid, precise and accurate enough for a routine method in various dairy products containing BLF.     

基于电子舌的乳制品品质特性及新鲜度评价

利用仪器快速、客观地评价乳制品的品质和新鲜度一直是乳制品相关研究的热点,利用课题组开发的多频脉冲电子舌,对5种品牌的UHT(超高温)灭菌纯牛乳和2种品牌的巴氏杀菌纯鲜牛乳进行了评价试验。采用主成分分析法进行数据处理。试验结果表明,电子舌可以很好地区分不同企业采用不同热处理工艺生产的牛乳产品;在室温(20℃)和冷藏(4℃)条件下,鲜牛乳品质随贮藏时间变化的特性也可以通过电子舌表征。电子舌作为一种新型的现代化智能感官仪器,在乳制品的品质及新鲜度评价中具有较大的潜力。     

Short communication: Norbixin and bixin partitioning in Cheddar cheese and whey

The Cheddar cheese colorant annatto is present in whey and must be removed by bleaching. Chemical bleaching negatively affects the flavor of dried whey ingredients, which has established a need for a better understanding of the primary colorant in annatto, norbixin, along with cheese color alternatives. The objective of this study was to determine norbixin partitioning in cheese and whey from full-fat and fat-free Cheddar cheese and to determine the viability of bixin, the nonpolar form of norbixin, as an alternative Cheddar cheese colorant. Full-fat and fat-free Cheddar cheeses and wheys were manufactured from colored pasteurized milk. Three norbixin (4% wt/vol) levels (7.5, 15, and 30 mL of annatto/454 kg of milk) were used for full-fat Cheddar cheese manufacture, and 1 norbixin level was evaluated in fat-free Cheddar cheese (15 mL of annatto/454 kg of milk). For bixin incorporation, pasteurized whole milk was cooled to 55°C, and then 60 mL of bixin/454 kg of milk (3.8% wt/vol bixin) was added and the milk homogenized (single stage, 8 MPa). Milk with no colorant and milk with norbixin at 15 mL/454 kg of milk were processed analogously as controls. No difference was found between the norbixin partition levels of full-fat and fat-free cheese and whey (cheese mean: 79%, whey: 11.2%). In contrast to norbixin recovery (9.3% in whey, 80% in cheese), 1.3% of added bixin to cheese milk was recovered in the homogenized, unseparated cheese whey, concurrent with higher recoveries of bixin in cheese (94.5%). These results indicate that fat content has no effect on norbixin binding or entrapment in Cheddar cheese and that bixin may be a viable alternative colorant to norbixin in the dairy industry.     

Assessment of aflatoxin M1 levels in selected dairy products in north‐western Iran

The purpose of this survey was to evaluate the natural occurrence and content of aflatoxin M_1, AFM_1, in dairy products marketed in Urmia. During September 2007, 40 samples of pasteurised milk, 40 samples of ultra high temperature‐treated (UHT) milk, 40 samples of creamy cheese and 40 samples of Iranian Feta cheese were collected from different supermarkets in Urmia city. AFM₁ contents were determined by the competitive enzyme‐linked imunosorbent assay (ELISA) technique. All milk samples analysed showed a mean of AFM₁ concentrations lower than the permissible level of 50 ng/kg in Iran (23.22 and 19.53 ng/kg in pasteurised milk and UHT milk respectively). The mean levels of AFM₁ contamination were 43.31 ng/kg in Feta cheeses and 21.96 ng/kg in creamy cheeses. The potential risk of human exposure to aflatoxin M₁ via consumption of milk and milk products is well known. Dairy products must therefore be evaluated for aflatoxin and kept free from fungal contamination as much as possible.     

The shelf-life of dairy products: 2. Raw milk and fresh products

In the second of this series of articles, the specific factors controlling the shelf-life of raw milk, pasteurized milk and cream, cottage cheese and yogurt are considered. The shelf-life of raw milk depends on the quality of the milk ex-farm and on subsequent transport and storage conditions. Shelf-life may be enhanced by deep cooling or thermization. Post heat treatment contamination by Gram negative psychrotrophic bacteria is the major determinant of shelf-life of pasteurized products. In cultured dairy products, yeast and mould contamination is the most usual cause of spoilage.     

High-Performance Liquid Chromatography Analysis and Assessment of Benzoic Acid in Yogurt, Ayran, and Cheese in Turkey

Among food sources, particular attention is paid to milk and dairy products, due to its nutritional importance. Benzoic acid is extensively used in the preservation of foods. A reliable method for the determination of benzoic acid in some dairy products, such as yogurt, ayran, and cheese using high-performance liquid chromatography and UV detection was validated. The peak of benzoic acid was measured at a wavelenght of 226 nm. Samples were purchased from supermarkets in Turkey in the period 2009–2010. All dairy product samples were produced from cow’s milk. The levels of benzoic acid in cheese, yogurt, and ayran samples were in the range of 3.17 to 56.77 mg kg⁻¹, 8.94 to 28.30 mg kg⁻¹, and 1.54 to 16.57 mg L⁻¹, respectively. The results show that benzoic acid widely occurs in milk products in Turkey at the low levels.     

酶联免疫吸附法快速测定不同样品 基质中三聚氰胺

目的 探求不同样品基质中三聚氰胺残留量的快速检测方法.为快速筛查不同种类食品中非法添加三聚氰胺提供技术保障.方法 采用酶联免疫吸附法在奶制品(奶粉、液态奶)、成品饲料(鸡饲料、猪饲料)、饲料原料(鱼粉、肉骨粉、豆粕、麸皮)、肉类(鸡肉、猪肉、内脏)等样品基质中添加一定浓度的三聚氰胺进行测定,并对检测结果进行分析.结果 酶联免疫试剂盒对奶制品和肉类检出限均能达到1.0 mg/kg;对成品饲料基质中的三聚氰胺的检测,检出限可达到2 mg/kg,而对饲料原料中的三聚氰胺的检测,检出限都不能达到2 mg/kg.结论 对奶制品中的三聚氰胺检测完全符合我国的临时限量标准;对成品饲料中的三聚氰胺残留的检测同样符合其限量标准(2.5 mg/kg),而对饲料原料中的三聚氰胺的检测,由于不同基质中检出限不同,不能直接采用酶联免疫法进行快速筛查;酶联免疫法也适用于肉类中的三聚氰胺的检测.     

Effect of dairy product environment on the growth of Bacillus cereus

pH is one of the most important parameters to manage bacterial replication in foodstuffs. In this study, the ability of 2 Bacillus cereus strains, 1 clinical human isolate (GPe2) and 1 isolate from a dairy product (D43), were investigated for in vitro growth at different pH values (from 3.5 to 7.5) at 2 temperatures (15 and 37°C), showing their ability to grow from 5.5 to 7.5 and from 5.0 to 7.5, respectively. The ability of spores of these 2 microorganisms to germinate in different typologies of dairy products (unflavored yogurt, Taleggio cheese, mascarpone cheese, and raw and pasteurized milk) was also investigated by inoculating the spores and maintaining the products at 15°C. No growth was observed in yogurt, likely due to the combined effect of low pH (<5) and the presence of natural microflora. An inhibitory action of the natural microflora on the growth of B. cereus was also hypothesized for Taleggio cheese and raw milk, as these substrates were characterized by a high natural lactic acid bacteria population and permissive pH values (5.8/6.8 in Taleggio cheese, >7 in raw milk). In pasteurized milk and mascarpone cheese, where pH was not restrictive for B. cereus growth and where no significant natural microflora was present, growth occurred rapidly up to loads close to 7 log cfu/g.     

Investigation of the migration of triclabendazole residues to milk products manufactured from bovine milk,and stability therein,following lactating cow treatment

Triclabendazole (TCB) is a flukicide used in the treatment of liver fluke in cattle; however, its use is currently prohibited in lactating dairy cows. In this study, following administration of 10% Fasinex (triclabendazole, Novartis Animal Health UK Ltd., Camberley, UK) the milk of 6 animals was used to manufacture dairy products, to ascertain if TCB residues in milk migrate into dairy products. The detection limit of the ultra-high-performance liquid chromatography-tandem mass spectrometry method used was 0.67 μg/kg. The highest concentrations of TCB residue measured, within the individual cow milk yield, was 1,529 ± 244 µg/kg (n = 6), on d 2 posttreatment. Days 2 and 23 posttreatment represented high and low residue concentrations, respectively. At each of these 2 time points, the milk was pooled into 2 independent aliquots and refrigerated. Milk products, including cheese, butter, and skim milk powder were manufactured using pasteurized and unpasteurized milk from each aliquot. The results for high residue milks demonstrated that TCB residues concentrated in the cheese by a factor of 5 (5,372 vs. 918 µg/kg for cheese vs. milk) compared with the starting milk. Residue concentrations are the sum of TCB and its metabolites, expressed as keto-TCB. Residues were concentrated in the butter by a factor of 9 (9,177 vs. 1,082 μg/kg for butter vs. milk) compared with the starting milk. For milk, which was separated to skim milk and cream fractions, the residues were concentrated in the cream. Once skim milk powder was manufactured from the skim milk fraction, the residue in powder was concentrated 15-fold compared with the starting skim milk (7,252 vs. 423 µg/kg for powder vs. skim milk), despite the high temperature (185°C) required during powder manufacture. For products manufactured from milk with low residue concentrations at d 23 posttreatment, TCB residues were detected in butter, cheese, and skim milk powder, even though there was no detectable residue in the milk used to manufacture these products. Triclabendazole residues were concentrated in some milk products (despite manufacturing treatments), exceeding residue levels in the starting milk and, depending on the storage conditions, may be relatively stable over time.     

配方注册婴幼儿配方乳粉中蛋白质及三聚氰胺含量测定分析

目的通过测定婴幼儿配方乳粉中蛋白质及三聚氰胺含量,对我国现阶段配方注册的婴幼儿配方乳粉安全状况进行监测。方法婴幼儿配方乳粉中蛋白质的含量依照GB 5009.5-2016《食品安全国家标准食品中蛋白质的测定》中"第一法凯氏定氮法"进行检测;三聚氰胺的含量依照GB/T22388-2008《原料乳与乳制品中三聚氰胺检测方法》中"第一法高效液相色谱法"进行检测。结果样品中蛋白质含量均符合食品安全国家标准规定,且满足测定值不小于标签标示值80%的规定;三聚氰胺的含量均为未检出或低于检出限,符合原卫生部公告的限量值规定。结论根据食品安全国家标准或推荐标准的检测方法和评价指标,所检测的样品中蛋白质项目满足配方注册要求。     

Inhibition of Listeria monocytogenes in dairy products using the bacteriocin-like peptide cerein 8A

The efficacy of the antimicrobial peptide cerein 8A to control the development of Listeria monocytogenes in milk and soft cheese was investigated. The addition of 160 AU ml(-1) cerein 8A to UHT milk resulted in a decrease of 3 log cycles in viable cells within the 14-day period at 4 degrees C. The viable counts of L. monocytogenes in pasteurized milk samples containing cerein 8A was lower than those observed in controls without bacteriocin. Addition of cerein 8A to Minas-type soft cheese caused a delay in the start of exponential growth phase, although similar counts were observed after day 6. When cerein 8A was used to control cheese surface contamination by L. monocytogenes, a decrease of 2 log cycles in viable counts of cerein-treated samples was observed during 30 days at 4 degrees C. This antimicrobial peptide shows potential use as a biopreservative for application in dairy products.     

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.     

Why semicarbazide (SEM) is not an appropriate marker for the usage of nitrofurazone on agricultural animals

A comprehensive global database on semicarbazide (SEM) in foodstuffs and food ingredients is presented, with over 4000 data collected in foods such as seafood (crustaceans, fish powders), meat (beef, chicken powders), dairy products (e.g. raw milk, milk powders, whey, sweet buttermilk powder, caseinate, yoghurt, cheese), honey and other ingredients. The results provide evidence that the presence of SEM in certain dairy ingredients (whey, milk protein concentrates) is a by-product of chemical reactions taking place during the manufacturing process. Of the dairy ingredients tested (c. 2000 samples), 5.3% showed traces of SEM > 0.5 µg/kg. The highest incidence of SEM-positive samples in the dairy category were whey (powders, liquid) and milk protein concentrates (35% positive), with up to 13 µg/kg measured in a whey powder. Sweet buttermilk powder and caseinate followed, with 27% and 9.3% positives, respectively. SEM was not detected in raw milk, or in yoghurt or cheese. Of the crustacean products (shrimp and prawn powders) tested, 44% were positive for SEM, the highest value measured at 284 µg/kg. Fish powders revealed an unexpectedly high incidence of positive samples (25%); in this case, fraudulent addition of shellfish shells or carry-over during processing cannot be excluded. Overall, the data provide new insights into the occurrence of SEM (for dairy products and fish powders), substantially strengthening the arguments that SEM in certain food categories is not a conclusive marker of the use of the illegal antibiotic nitrofurazone.     

Influence of thermal processing conditions on flavor stability in fluid milk: benzaldehyde

Flavor loss in dairy products has been associated with enzymatic degradation by xanthine oxidase. This study was conducted to investigate the influence of milk thermal processing conditions (or xanthine oxidase inactivation) on benzaldehyde stability. Benzaldehyde was added to whole milk which had been thermally processed at 4 levels: (1) none or raw, (2) high temperature, short time (HTST) pasteurization, (3) HTST pasteurization, additionally heated to 100 degrees C (PAH), and (4) UHT sterilized. Additionally, PAH and UHT milk samples containing benzaldehyde (with and without ferrous sulfate) were spiked with xanthine oxidase. Azide was added as an antimicrobial agent (one additional pasteurized sample without) and the microbial load (total plate count) was determined on d 0, 2, and 6. The concentration of benzaldehyde and benzoic acid in all milk samples were determined at d 0, 1, 2, 4, and 6 (stored at 5 degrees C) by gas chromatography/mass spectrometry in selective ion monitory mode. Over the 6-d storage period, more than 80% of the benzaldehyde content was converted (oxidized) to benzoic acid in raw and pasteurized milk, whereas no change in the benzaldehyde concentration was found in PAH or UHT milk samples. Furthermore, the addition of xanthine oxidase or xanthine oxidase plus ferrous sulfate to PAH or UHT milk samples did not result in benzaldehyde degradation over the storage period.     

UPLC-MS/MS测定婴幼儿配方乳粉中双酚A和壬基酚

建立一种测定婴幼儿配方乳粉中双酚A和壬基酚的超高效液相色谱串联质谱准确定性定量方法。向配方乳粉样品中加水溶解,乙腈提取,使用在线捕集技术消除流动相中的本底影响,以甲醇-0.1%氨水溶液作为流动相在C₁₈色谱柱上进行梯度洗脱,用超高效液相色谱仪进行分离后,通过电喷雾负离子模式电离,多反应检测模式进行检测分析,内标法准确定量。结果表明:在1~2000 ng/mL范围内呈良好的线性关系,相关系数大于0.999。本方法BPA和NP检出限均低至0.1 μg/kg,在不同婴幼儿配方乳粉中添加1、10、100 μg/kg三水平加标,测定结果平均回收率在89.5%~102.8%之间,相对标准偏差为1.3%~4.8%,该方法具有较高的灵敏度和准确度。对市售200份婴幼儿配方乳粉进行测定,检出BPA含量为0.1~30.0 μg/kg,检出NP含量为1.1~105 μg/kg,适合婴幼儿配方乳粉中双酚A和壬基酚的定量测定。     

Some aspects of the periurban dairy system in Cameroon

A survey to establish baseline data for future intervention in milk and dairy production in the peri-urban areas of Garoua, Maroua and Bamenda was carried out. Dairy products are still produced in a traditional way in areas around Maroua and Garoua with milk from native zebu cattle (Red and White Fulani breeds). The important dairy products are pendidam and kindirmu, both of which are fermented milks. Naturally sour milk was found occasionally. Around Bamenda, milk is produced by herds comprising pure Holsteins, Jerseys and their crosses with local zebu cows; cross-breeding is being intensified to increase rapidly the size of the dairy herds. Appreciable volumes of milk are produced daily, so allowing the industrial processing of fresh milk into pasteurized milk, yogurt and cheese. The potential for expansion of the dairy industry, and the possible constraints, were identified and solutions proposed.     

Effect of Transglutaminase on Physicochemical Properties of Set-style Yogurt

In this study, the effect of some ingredients such as skimmed milk powder, whey, sodium caseinate, calcium caseinate, whey protein concentrate (35, 60 kg/100 kg dry solids), whole milk powder, condensed milk and transglutaminase (TGase) on the properties of set-style yogurt was investigated. These protein and dry matter sources (2%) and TGase (1 U/g milk protein) were added into pasteurized milk and incubated prior to fermentation for 2 h at 40°C. After fermentation, enzyme action was stopped by heating for 1 min at 80°C. The control groups were conducted with addition of these materials into milk without TGase. All of the milk samples were inoculated with yogurt cultures at 45°C, until the pH was dropped to 4.4. Syneresis, gel-strength, acetaldehyde amounts, and the degree of TGase reaction were determined. As a result, yogurt products made from enzyme-treated milk showed increased gel strength and less syneresis. SDS-PAGE results showed that the enzyme TGase produced crosslink formation between different protein fractions of milk. In addition, it was also determined that TGase application caused a decrease in acetaldehyde amounts.     

Fate of ivermectin residues in ewes' milk and derived products

The fate of ivermectin (IVM) residues was studied throughout the processing of daily bulk milk from 30 ewes (taken up to 33 d following subcutaneous administration of 0.2 mg IVM/kg b.w.) in the following milk products: yoghurt made from raw and pasteurized milk; cheese after pressing; 30- and 60-day ripened cheese; and whey, secondary whey and whey proteins obtained after cheese-making (albumin cheese). The concentration of the H2B1a component of IVM was analysed in these dairy products using an HPLC method with fluorescence detection. The mean recovery of the method was, depending on the matrix, between 87 and 100%. Limits of detection in the order of only 0.1 microg H2B1a/kg of product were achieved. Maximum concentrations of IVM were detected mostly at 2 d after drug administration to the ewes. The highest concentration of IVM was found on day 2 in 60-day ripened cheese (96 microg H2B1a/kg cheese). Secondary whey was the matrix with the lowest concentration of IVM (<0.6 microg H2B1a/ kg). Residue levels fell below the limits of detection between day 5 (for secondary whey) and day 25 (for all cheese samples). In the matrices investigated, linear correlations between daily concentrations of IVM, milk fat and solid content were evident. During yoghurt production, fermentation and thermal stability of IVM was observed. During cheese production, approximately 35% of the IVM, present in the raw (bulk) milk samples, was lost. From the results it was concluded that the processing of ewes' milk did not eliminate the drug residues under investigation. The consequences of IVM in the human diet were discussed. Milk from treated animals should be excluded from production of fat products like cheese for longer after treatment with IVM than for lower fat products.