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.     

Quantification of oxytocin residues in dairy milk from Sindh,Pakistan

In this study, a total of 84 milk samples (60 nonbranded and 24 branded) were analysed for occurrence of oxytocin (OT) residues by ELISA. OT level was detected in the range of 39.29–456.55 pg mL^?1 with mean value of 138.53 ng L^?1. In branded milk samples, OT residues were minimal as compared to nonbranded milk samples. Nonbranded milk samples had higher prevalence of OT residues; 16.67% had OT level in the range of ≤500 ng L^?1. The average daily intake of OT was found 0.087 μg day^?1 per person. It was concluded that the OT concentration was relatively higher in samples obtained from dairy farm, dairy shop and milk man than that in ultra‐high temperature (UHT) and powder milk samples. In addition, there are no reports subjected to standardising a permissible OT level in dairy milk category, although OT is considered detrimental to both human and animal life.     

Survey of clenbuterol in bovine muscle and liver in Ecuador

ABSTRACT

Clenbuterol is a steroid-type drug used in respiratory treatments in both humans and animals. However, it has a secondary effect related to the hypertrophy process in muscle and fat reduction. The illegal or bad use of clenbuterol has been reported in several countries, but there is scarce information in South America, where the production and consumption of meat are considerable. In this sense, the present study aimed at evaluating the occurrence of clenbuterol in bovine muscle and liver samples from a high cattle production area of Ecuador in 2015 and 2018. For this purpose, 57–58 samples were evaluated in 2015 and 20 samples in 2018 using the Enzyme-Linked Inmuno Sorbent Assay and ultrahigh-performance liquid chromatography-tandem mass spectrometry. The results showed complained results for clenbuterol in meat samples from both years and 23% (2015) and 85% (2018) of the samples of meat complied the maximum residue level defined by CODEX.     

Stability of cefacetrile in milk samples with various fat content

The consumers should have access to food that is safe and free of contaminants. Unfortunately, the wide use of antibiotics in livestock, not only for medicinal purposes but also as illegal feed additives, may be the reason for emergence of the antibiotic residues in foodstuffs of animal origin. Milk is one of the most essential nutrients for humans during their lifetimes. Failure of the withdrawal periods, or what is highly prohibited but in spite of this increasingly practiced, addition of the antibiotics to milk in order to prolong its freshness, may lead to occurrence of their residues. Cefacetrile is a first generation cephalosporin that is commonly use for the treatment of bovine mastitis. The aim of this work was to determine the stability of cefacetrile in milk samples of different fat content, that is, 0 , 2 , 3.2 % UHT, 2 % pasteurized and ~3.9 % raw cattle milk, for 5 days. Two chromatographic methods were applied and compared for this purpose, that is, thin-layer chromatography and high-performance liquid chromatography. According to the results coming from HPLC-UV analysis, the stability of cefacetrile increase with the increase in the fat mass content in UHT milk. The cefacetrile level in pasteurized and raw cattle milk is similar to that in 3.2 % UHT milk. For the TLC method, this relation can be observed only in the second day of the analysis. The spiked milk samples analyzed by HPLC were deproteinized with MeCN and stored for 5 days of the experiment. Whereas, in the TLC-UV method, the spiked milk samples prepared in the first day of experiment were analyzed directly, without deproteinization. The lower stability of cefacetrile in milk samples observed from the TLC analysis can be related to its partial enzymatic decomposition.     

Occurrence of aflatoxin M1 in raw and market milk commercialized in Greece

From December 1999 to May 2000, 114 samples of pasteurized, ultrahigh temperature-treated (UHT) and concentrated milk were collected in supermarkets, whereas 52 raw milk samples from cow, sheep and goat were obtained from different milk producers all over Greece. Sample collection was repeated from December 2000 to May 2001 and concerned 54 samples of pasteurized milk, 23 samples of bulk-tank raw milk and 55 raw milk samples from cow, sheep and goat. The total number of samples analysed for aflatoxin M₁ (AFM₁) contamination by immunoaffinity column extraction and liquid chromatography was 297. In the first sampling, the incidence rates of AFM 1 contamination in pasteurized, UHT, concentrated and cow, sheep and goat raw milk were 85.4, 82.3, 93.3, 73.3, 66.7 and 40%, respectively, with only one cow raw milk and two concentrated milk samples exceeding the EU limit of 50 ng l^-1. In the second sampling, the incidence rates of AFM 1 contamination in pasteurized, bulk-tank and cow, sheep and goat raw milk were 79.6, 78.3, 64.3, 73.3 and 66.7%, respectively, with only one cow and one sheep raw milk samples exceeding the limit of 50 ng l^-1. The results suggest that the current regulatory status in Greece is effective.     

Assessment of proteolysis in ultra‐high temperature milk using attenuated total reflectance–Fourier transform infrared spectroscopy

This study investigated the suitability of attenuated total reflectance–Fourier transform infrared spectroscopy (ATR‐FTIR) as an alternative technique to assess proteolysis in ultra‐high temperature (UHT) milk. Commercial UHT milk samples were stored (5 and 30 °C) and analysed for four months. Milk samples were treated with acetic acid and trichloroacetic acid to obtain milk extracts containing peptides. The concentrated extracts were subjected to ATR‐FTIR, and the spectrum was obtained. Results were compared with techniques like high‐performance liquid chromatography, fluorescamine and 2,4,6‐trinitrobenzenesulphonic acid. The present study indicated that ATR‐FTIR‐based method can be used as an alternative method for assessing proteolysis in UHT milk.     

Occurrence of aflatoxins M(1) and M(2) in milk commercialized in Ribeir?o Preto-SP, Brazil.

Aflatoxins are toxic metabolites found in foods and feeds. When ruminants eat foodstuffs containing aflatoxins B(1) and B(2), these toxins are metabolized and excreted as aflatoxin M(1) and M(2) in milk. The aim was to determine the incidence of these aflatoxins in commercial milk collected from supermarkets in Ribeir?o Preto-SP, Brazil, and consisting of 60 ultrahigh temperature (UHT) milk samples and 79 pasteurized milk samples. The milk samples were analysed according to method 986.16 of AOAC International. None of the milk samples analysed were contaminated with aflatoxin M(2), and aflatoxin M(1) was detected in 29 (20.9%) of samples in the range 50-240 ng l(-1). The results show that despite a high occurrence of aflatoxin M(1) in commercial pasteurized and UHT milk sold in Ribeir?o Preto in 1999 and 2000, the contamination level of these toxins could not be considered a serious public health problem according to MERCOSUR Technical Regulations. However, levels in 20.9% of the milk samples exceeded the concentration of 50 ng l(-1) permitted by the European Union. Although it is not necessary to continue monitoring the incidence and levels of aflatoxins M(1) and M(2) in milk samples, surveillance could be appropriate.     

UHT Milk Processing and Effect of Plasmin Activity on Shelf Life: A Review

Abstract: The demand for ultra‐high‐temperature (UHT) processed and aseptically packaged milk is increasing worldwide. A rise of 47% from 187 billion in 2008 to 265 billon in 2013 in pack numbers is expected. Selection of UHT and aseptic packaging systems reflect customer preferences and the processes are designed to ensure commercial sterility and acceptable sensory attributes throughout shelf life. Advantages of UHT processing include extended shelf life, lower energy costs, and the elimination of required refrigeration during storage and distribution. Desirable changes taking place during UHT processing of milk such as destruction of microorganisms and inactivation of enzymes occur, while undesirable effects such as browning, loss of nutrients, sedimentation, fat separation, cooked flavor also take place. Gelation of UHT milk during storage (age gelation) is a major factor limiting its shelf life. Significant factors that influence the onset of gelation include the nature of the heat treatment, proteolysis during storage, milk composition and quality, seasonal milk production factors, and storage temperature. This review is focused on the types of age gelation and the effect of plasmin activity on enzymatic gelation in UHT milk during a prolonged storage period. Measuring enzyme activity is a major concern to commercial producers, and many techniques, such as enzyme‐linked immunosorbent assay, spectrophotometery, high‐performance liquid chromatography, and so on, are available. Extension of shelf life of UHT milk can be achieved by deactivation of enzymes, by deploying low‐temperature inactivation at 55 °C for 60 min, innovative steam injection heating, membrane processing, and high‐pressure treatments.     

Development of an improved extraction and HPLC method for the measurement of ascorbic acid in cows' milk from processing plants and retail outlets

An improved extraction (2.5% HPO₃, 5 mm dithiothreitol) and HPLC quantification methodology using a C–18 column at 35 °C and 0.1 m acetic acid (98%) and acetonitrile (2%) mobile phase was developed to quantify total ascorbic acid (AA) in commercial whole/semi‐skim/skim raw/pasteurised/UHT milk packaged in opaque bags, transparent plastic, cardboard and Tetra Brik^?. AA content ranged from 0.21 to 10 and from 3.4 to 16 mg L^?1 in milk from retail outlets and processing plants, respectively, and was higher in organic milk. For same processor/lot samples, pasteurised milk showed higher AA content than UHT milk. This was not true for retail outlets samples. AA content was similar for whole/semi‐skim and semi‐skim/skim milk, but not for whole/skim comparisons. Among UHT samples, the AA content trend was whole<semi‐skim<skim and lower for UHT milk in opaque plastic and Tetra Brik^? container. After 14 days at 4 °C in the dark, AA losses ranged 35–83% depending on milk type and preservation method with a higher AA retention in unopened containers.     

DETECTION OF ANTIMICROBIAL DRUG RESIDUES IN KENYAN MILK

The improved Dutch tube diffusion test was used to study the occurrence of inhibitory substances in raw bulk milk samples within the Nakuru District in Kenya. Initially the detection limits of the method were verified using milk standards spiked with selected antibiotics. Addition of penicillinase to inhibitor-positive samples was used for preliminary identification of penicillin G-type antibiotics and residue levels were estimated against a standard curve constructed by means of a B. stearothermophilus disc assay. The two-tube test was used to screen 1109 field samples of which 229 (21%) were suspect positive. The identification procedure confirmed 165 samples (14.9%) to contain penicillin G-type residues of which 118 contained levels exceeding the established EU MRL for penicillin G (4 μg/kg). This study indicates that antibiotic residues are prevalent in milk within the Nakuru district of Kenya. It suggests that the improved tube diffusion test in combination with a multiplate system could be useful for qualitative and quantitative identification of antimicrobial drug residues in milk.     

Efficacy of cellulase and mannanase hydrolysates of konjac glucomannan to promote the growth of lactic acid bacteria

BACKGROUND: Glucomannan polysaccharides may be hydrolysed to lower molecular weight molecules using acids or enzymes, specifically mannanases or cellulases. Mannanases (β‐mannanases) hydrolyse β‐(1–4)‐linked mannose residues randomly in mannans whilst cellulases (β‐glucanase) hydrolyse β‐(1–4)‐linked glucose residues. The molecular weight of the hydrolysate is clearly dependent on the amount of hydrolysis. One use of such hydrolysates has been towards their capacity to function as prebiotics. The relative efficacy of cellulase and/or mannanase hydrolysates of konjac glucomannan to promote the growth of lactic acid bacteria (LAB) has been evaluated. RESULTS: The LAB growth profiles (expressed in colony forming units, as a function of time) in UHT milk containing konjac glucomannan hydrolysed with cellulase were significantly greater than those containing glucose (control) or konjac glucomannan mannanase hydrolysates. An equivalent mixture (1:1) of cellulase–mannanase hydrolysates added to the UHT milk also showed significant improvement on the LAB growth profiles (compared to the glucose or mannanase alone hydrolysates). Different LAB strains showed some variation in growth profiles on the hydrolysates although this was not significant as a function of carbon source. CONCLUSIONS: Glucomannan hydrolysates produced with either mannanase or cellulase enzymes were effective growth promoters (carbon sources) of LAB. However, cellulase hydrolysates were most effective. Copyright © 2012 Society of Chemical Industry     

Determination of whey protein to total protein ratio in UHT milk using fourth derivative spectroscopy

A fourth derivative spectroscopy method was applied for the quantification of whey protein to total protein ratio in UHT milks. Some analytical features such as model compounds, selection of wavelength, linearity, repeatability and interference of milk fat were studied. The effect of refrigerated storage of raw milk, UHT treatment, and storage of UHT milk at room temperature on whey protein to total protein ratio was evaluated. No significant (p<0.05) differences among samples were found in any case. The ratio of whey protein to total protein was also determined in batches of whole (n=28) and skimmed (n=27) commercial UHT milks from different Spanish geographic areas processed by direct or indirect UHT systems in different periods of the year. The mean value was 18.1% for both whole and UHT skimmed milks. The analysis of laboratory-made mixtures of UHT milk with acid and rennet whey (2.5–15% of whey in milk expressed in protein) indicated that adulterations of UHT milk with whey up from 5% could be detected by the proposed method.     

酸性品红-B-R体系共振光散射法测定牛奶中的新霉素

为建立一种快速测定牛奶中新霉素的新方法,以市售超高温灭菌纯牛奶为样品,基于样品中残留新霉素与酸性品红在pH5.50的B-R(Britton-Robinson)缓冲溶液中形成新的缔合物,利用共振光散射技术进行测定。结果表明：其最大共振光散射峰位于625nm波长处,在0.00～2.50μg/mL范围内新霉素质量浓度与体系的相对散射光强度(ΔI)有良好的线性关系,相关系数r=0.9978,检出限为0.013μg/mL;样品测定的RSD小于2.5%(n=5),加标回收率为84.0%～96.7%。此法快速简便、灵敏度较高,用于牛奶中新霉素残留量的测定,结果满意。     

Incidence and characterisation of aerobic spore‐forming bacteria originating from dairy milk in Tunisia

The purpose of this study was to evaluate the incidence and characterisation of aerobic spore‐forming bacteria originating from dairy milk in Tunisia. The distribution of Bacillus species in raw milk, pasteurised milk and UHT milk were 47.5%, 27.5% and 25%, respectively. Seven Bacillus species, including Bacillus pumilus (10%), Bacillus subtilis (12.5%), Brevibacillus brevis (10%), Bacillus cereus (22.5%), Bacillus sphaericus (7.5%), Bacillus licheniformis (12.5%) and Bacillus sporothermodurans (25%) were identified in different milk samples. Bacillus cereus was predominant in raw and pasteurised milk. Although B. sporothermodurans was the predominant sporogenous micro‐organism in UHT milk, B. cereus, B. sphaericus and B. licheniformis were also present. This study showed that there is a high degree of diversity, both phenotypic and genotypic, among Bacillus isolates from Tunisian milk and the persistence of spoilage risk in UHT milk.     

PAHs concentration in heat-treated milk samples

In this study the presence of residual levels of Polycyclic Aromatic Hydrocarbons (PAHs) in milk samples from Calabria was evaluated. A comparative analysis of PAHs concentrations was conducted on raw, pasteurized, UHT semi-skimmed and whole milk.Quantitative determination of PAHs was performed by HPLC using a fluorescence detector and analysis in HPLC-MS was conducted to confirm the presence of these compounds.Residual levels of PAHs were found in all milk samples analyzed, showing higher concentrations in pasteurized and UHT milk than in raw milk samples.The results obtained demonstrate that PAHs presence also in raw milk is dependent from environmental pollution but pasteurization and UHT treatments of milk can influence PAHs formation; the differences found between whole and semi-skimmed samples can be due to different fat content of milk.     

UHT乳贮藏期间理化特性和感官品质的变化

为探讨超高温瞬时杀菌(ultra-high temperature instantaneous sterilization,UHT)乳的营养价值随贮藏时间的变化,对不同贮藏期UHT乳的理化特性和感官品质进行监测。在6个月的贮藏期内,UHT乳中脂肪、蛋白质、乳糖以及固形物的总量并无明显变化,维生素C和泛酸的含量均损失了约25%,游离氨基酸和钙离子分别增加了5.35%和6.73%。不同贮藏期UHT乳的黏度变化不显著(P>0.05),但粒径大小强烈依赖于贮藏时间,乳脂肪球和酪蛋白胶束的尺寸在贮藏初期分别增加了约38 nm和14 nm,然后分别稳定在约173 nm和612 nm。贮藏1个月的UHT乳样品在风味和口感方面整体表现较好,贮藏6个月后,UHT乳的感官品质大幅下降,出现了许多不良风味。     

Flow injection chemiluminescent determination of clenbuterol using GoldMag particles as carrier

A novel flow injection chemiluminescent (CL) enzyme immunoassay for clenbuterol analysis based on GoldMag particles is described. GoldMag is a new type of super-paramagnetic Fe₃O₄/Au composite particle used as a carrier in a flow injection CL system. Clenbuterol conjugated with ovalbumin (OVA) was immobilized onto GoldMag particles and the particles fixed in a micro-channel by an external electromagnetic field. The clenbuterol test sample and clenbuterol polyclonal antibody (Ab) were injected into the channel and incubated with GoldMag particles. Clenbuterol, immobilized on the magnetic particle surfaces, competes for polyclonal antibodies with clenbuterol in the test sample. The free Ab or Ab combined with the clenbuterol sample was washed away and the magnetic particles conjugated with Ag-Ab left in the micro-channel. Horseradish peroxidase (HRP)-labelled goat anti-rabbit immunoglobulin G (IgG) was added and reacted with clenbuterol polyclonal antibodies; excess goat anti-rabbit-HRP was then washed off. When chemiluminescent reagents were injected into the channel, emitted light from the magnetic particle surface was measured and recorded using a photomultiplier-based apparatus. The linear range of this novel method was 0.01-0.1 ng g^-1 and recovery of clenbuterol was 85-105% with a RSD of 3.2% (n = 11).     

Seasonal and regional occurrence of heat-resistant spore-forming bacteria in the course of ultra-high temperature milk production in Tunisia

Spore-forming bacteria, principally Bacillus species, are important contaminants of milk. Because of their high heat resistance, Bacillus species spores are capable of surviving the heat treatment process of milk and lead to spoilage of the final product. To determine the factors influencing the contamination of milk, spore-forming bacteria occurrence throughout the UHT milk production line during winter, spring, and summer was studied. The obtained results confirm that the total viable rate decreases rapidly throughout the production line of UHT milk showing the efficiency of thermal treatments used. However, the persistent high rate of spore-forming bacteria indicates their high heat resistance, especially in spring and summer. In addition, a significant variation of the quality of raw milk according to the location of the collecting centers was revealed. The molecular identification showed a high degree of diversity of heat-resistant Bacillus species, which are isolated from different milk samples. The distribution of Bacillus species in raw milk, stored milk, bactofuged milk, pasteurized milk, and UHT milk were 28, 10, 16, 13, and 33%, respectively. Six Bacillus spp. including Bacillus licheniformis (52.38%), Bacillus pumilus (9.52%), Bacillus sp. (4.76%), Bacillus sporothermodurans (4.76%), Terribacillus aidingensis (4.76%), and Paenibacillus sp. (4.76%) were identified in different milk samples.     

Occurrence of endosulphan residues in dairy milk in plains of Uttarakhand,India: Short communication

Endosulphan residues were determined in milk samples collected from various locations of plains of Uttarakhand covering Tarai and Kumaon regions. Residues were extracted from milk by liquid–liquid partition followed by clean‐up by alumina column chromatography. High‐performance liquid chromatography (HPLC) was used for the detection and quantification of residues. Of the total 170 milk samples collected from different species, 1.17% samples showed residues of endosulphan‐alpha; 2.35% endosulphan β and 4.7% milk samples showed endosulphan‐sulphate residues with mean residual concentrations of 0.244, 0.566 and 0.265 μg/mL, respectively. About 6.47% of milk samples showed endosulphan residues above the maximum residue limit (MRL) of 0.1 mg/kg.     

Effect of addition of CO₂ to raw milk on quality of UHT-treated milk

The objective of this study was to evaluate the effect of addition of CO(2) to raw milk on UHT milk quality during storage. Control milk (without CO(2) addition) and treated milk (with CO(2) addition up to pH 6.2) were stored in bulk tanks at 4°C for 6d. After storage, both samples were UHT processed using indirect heating (140°C for 5s). Samples were aseptically packed in low-density polyethylene pouches and stored in the dark at room temperature. Raw milk was evaluated upon receipt for physicochemical composition, proteolysis, lipolysis, standard plate count, psychrotrophic bacteria, and Pseudomonas spp. counts, and after 6d of storage for proteolysis, lipolysis, and microbial counts. After processing, UHT milk samples were evaluated for physicochemical composition, proteolysis, and lipolysis. Samples were evaluated for proteolysis and lipolysis twice a month until 120d. Peptides from pH 4.6-soluble N filtrates were performed by reversed-phase HPLC after 1 and 120d of storage. A split-plot design was used and the complete experiment was carried out in triplicate. The results were evaluated by ANOVA and Tukey's test. After 6d of storage, CO(2)-treated raw milk kept its physicochemical and microbiological quality, whereas the untreated milk showed significant quality losses. A significant increase in proteolysis occurred during 120d of storage in both treatments, but the increase occurred 1.4 times faster in untreated UHT milk than in CO(2)-treated UHT milk. In both UHT milks, the proteolysis was a consequence of the action of plasmin and microbial proteases. However, the untreated UHT milk showed higher microbial protease activity than the treated UHT milk. The addition of CO(2) to the raw milk maintained the quality during storage, resulting in UHT milk with less proteolysis and possibly longer shelf life, which is usually limited by age gelation of UHT milk.