Occurrence and seasonality of aflatoxin M1 in milk in two different climate zones.

BACKGROUND: Aflatoxin M1 (AFM1) is a mycotoxin found in milk as a result of the ingestion of aflatoxin B1 (AFB1) by dairy cattle. Because of its carcinogenic properties, the control of its occurrence in dairy products is of great importance. We evaluated the occurrence and seasonality of AFM1 in milk from farms with subtropical and temperate climates, where significant milk production occurs. Forty samples of raw milk were collected from bulk tansk milk during the summer (five samples from a subtropical climate and 14 from a temperate climate) and winter (six samples from a subtropical climate and 15 from a temperate climate) months of 2017 and conducted an analysis using an enzyme-linked immunosorbent assay (ELISA) (detection limit 5 ng L-1 ). Data from eight random samples were compared with respect to liquid chromatography with mass spectrometry detection and ELISA. A significant correlation was observed. RESULTS: The presence of AFM1 was detected in 87.50% (n = 35) of the samples analyzed (a mean of 16.66 ng L-1 and a median of 12.42 ng L-1 in positive samples); however, its concentration in all samples was below the maximum limit allowed by European (50 ng L-1 ) and Brazilian (500 ng L-1 ) legislations. There were no significant differences in the levels of AFM1 between the properties located in the two climate zones, in both summer and winter. The estimated daily intake of AFM1 based on the milk analyzed was 0.0107 ng kg-1 day-1 for adolescents, 0.0072 ng kg-1 day-1 for adults and 0.0098 ng kg-1 day-1 for the elderly. CONCLUSION: The present work demonstrated a low exposure to AFM1. © 2018 Society of Chemical Industry.

Changes occurring in stabilized ultra-high-temperature-treated whole milk during storage.

This Research Communication describes the relationship between casein, free fatty acids (FFAs) and the storage period of ultra-high temperature-treated (UHT) whole milk observed for a period of 120 d of labelled shelf-life. Moreover, we aim to estimate the daily rate of casein degradation in UHT whole milk, and the total length of time estimated for its full degradation. With this aim, ten sets of samples were evaluated from batches of UHT milk manufactured by a dairy processing plant in Parana State, Brazil on 10 different days. Each set was comprised of one liter of raw milk and 12 units of 1 litre cartons of UHT milk, and represented one batch of production. Total mesophilic (TMC), psychrotrophic (TPC), and somatic cell counts (SCC) of raw milk were assessed. UHT milk was assessed for fat (%), sialic acid (mg/l), casein (%), and FFA contents. TMC ranged from 3·5 × 106 to 3·1 × 107 CFU/ml; TPC, from 106 UFC/ml and higher; and SCC, from 18 × 104 SC/ml to 4·83 × 105 CS/ml. Casein (r = -0·991; R2 = 0·9822) and FFA (r = 0·962; R2 = 0·9245) contents, and storage time of UHT milk were correlated (P < 0·05). The rate of casein hydrolysis was estimated as 0·021 g/100 g UHT whole milk/day. A complete breakdown of casein was estimated to occur by the 560th day post-manufacture. Although age gelation was not observed in our study, the report herein corroborates the understanding that the microbiological quality and SCC of raw milk are important components involving the integrity of casein and lipids of UHT milk during shelf-life.

Milk adulteration with acidified rennet whey: a limitation for caseinomacropeptide detection by high-performance liquid chromatography.

BACKGROUND: High-performance liquid chromatography (HPLC) is widely employed to determine the caseinomacropeptide (CMP) index and to detect milk tampering with rennet whey. Prior to HPLC analysis, CMP is subject to a trichloracetic acid isolation, causing further soluble proteins in the sample to precipitate. On this basis, we aimed to determine whether rennet whey acidification could adversely affect the HPLC sensitivity with respect to detecting this peptide. RESULTS: As hypothesized, the CMP index from milk with added acidified rennet whey was, on average, half that quantified from milk with added rennet whey. Moreover, the quantum satis of acidified whey added to milk sufficient to demonstrate a HPLC CMP > 30 mg L-1 was 94% greater than that required for this threshold to be reached with rennet whey. CONCLUSION: Milk tampering with acidified rennet whey may limit the analytical sensitivity of the reversed-phase HPLC employed for the screening of CMP and, ultimately, disguise the fraudulent addition of whey to milk. © 2017 Society of Chemical Industry.

Viability of probiotic Lactobacillus casei in yoghurt: defining the best processing step to its addition.

Probiotics are live microorganisms capable of producing beneficial effects on its host when consumed in adequate amounts. To exert these effects, foods must contain probiotic microorganisms in populations above 10(6) CFU/g or mL throughout its shelf life. One of the strategies to ensure high population of probiotics in fermented milk is to add them during or after the fermentation process separately from the starter cultures. The objective of this study was to investigate the behavior of the probiotic microorganism Lactobacillus casei added to yoghurt in different stages of production. Yoghurts with L. casei were produced at different stages: before addition of starter (Streptococcus salivarius subsp. thermophilus and Lactobacillus delbrueckii subsp. bulgaricus), added together with this culture and at the end of fermentation. Yoghurt without probiotic added was produced as a control. The products were stored at 4 degrees C and analyzed after 1, 7, 14 and 21 days of storage. In these periods, the populations ofprobiotic and starter cultures were enumerated and the parameters pH and acidity were analyzed. The results were evaluated using analysis of variance and Tukey's test, both at 5% significance level. L. casei remained viable in populations of more than 10(8) CFU / g during 21 days of storage, which is suitable to define the formulations as probiotics. When the different stages of the addition of probiotics in yoghurts were evaluated there was no statistical difference between the formulations (p < 0.05) for populations of L. casei except for the first day of storage.

Antimicrobial action of lactoferrin on Staphylococcus aureus inoculated in Minas frescal cheese.

The effect of the addition of lactoferrin on Staphylococcus aureus to Minas frescal cheese was evaluated. Three cheeses were made: control (S. aureus), Lf-2% (2% lactoferrin + S. aureus) and Lf-4% (4% lactoferrin + S. aureus). Cheeses were packaged and S. aureus populations were determined on days 1, 8, 15, 22 and 29 of storage at 6 degrees C. The experiment was repeated three times. S. aureus population increased 1.3 logarithmic cycles in the control cheese during storage, while it decreased to numbers below the detection limit in cheeses containing lactoferrin, over the same period. Moreover, antimicrobial effect showed to be dose-dependent.

[Physico-chemical and microbiological evaluation of UHT milk commercialized in three Mercosul countries (Brazil, Argentina and Paraguay)]. / Avalição físico-química e microbiológica do leite UHT comercializado em três países do Mercosul (Brasil, Argentina e Paraguai).

With the aim to evaluate the physico-chemical and microbiological quality of UHT milk commercialized in three countries of Mercosul, samples of four different brands were acquired in each city (Foz do Iguaçu-Brazil, Puerto Iguazú-Argentina and Ciudad del Este-Paraguay) and submitted to the following analysis: fat content, titratable acidity, milk ethanol stability (with the following ethanol concentrations: 68, 72, 76 and 80%), total dry extract and no fat dry extract, pH, density and freezing point. Counts of mesophilic and psychrotrophic microorganisms were already done. In the physico-chemical evaluation of UHT milk, a significant number of samples were in disagree with the established patterns for fat content, no fat dry extract, density and freezing point. Except one brand from Brazil, milk samples showed stability to 68% ethanol. pH averages of Brazilian milk were in agree with the patterns and highest values were observed in samples acquired on Paraguay. Observing the microbiological analysis, 37.5%, 62.5% and 12.5% of samples acquired from Brazil, Argentina and Paraguay, respectively, showed counts above the established patterns for mesophilic microorganisms. Counts of psychrotrophic microorganisms were in disagree with the established patterns in 50%, 50% and 100% of samples from Brazil, Argentina and Paraguay, respectively.