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.

Field findings about milk ethanol stability: a first report of interrelationship between α-lactalbumin and lactose.

BACKGROUND: Milk ethanol stability is not only associated with microbiological acidification, but is a phenomenon with many variables that influence the balance of soluble salts, mainly calcium ion activity. On this basis, we wanted to find out more about milk ethanol stability by studying its relationship with milk protein fractions and others major components. The influence of milk composition on ethanol stability was assessed through a predictive model comprising 180 individual raw milk samples. An additional model was used to assess the ethanol stability status as a response to the proteins fractions quantified by electrophoresis. RESULTS: Of the total samples, 68% were classified as stable and 32% as unstable to alcohol. Milk ethanol instability increased at low values of lactose content and high values of ash percentage. α-Lactalbumin (α-La) was also associated with ethanol stability, and the higher the α-La percentage the lower were the chances of ethanol instability. CONCLUSION: The lower values of α-La in unstable milk samples might be related to lower content of lactose, as α-La promotes lactose synthesis, a key component for the osmotic balance of milk and thus its ethanol stability. This is the first field report linking ethanol stability indirectly with α-La. © 2017 Society of Chemical Industry.

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.

Herd characteristics and management practices associated with bulk tank milk quality of dairy herds in southeastern Brazil.

This study identified the association of management practices and herd characteristics with milk quality of bulk tanks in southeastern, Brazil. Milk samples were collected weekly during 8 weeks from 63 dairy herds. Bulk tanks were evaluated for total bacteria (TBC), preliminary incubation (PIC), pasteurization (PC), coliform (CC), and somatic cell counts (SCC). Associations found were type of milking system utilized in the farm with TBC, PIC, and SCC; the use of gloves for milking with TBC and PIC; sanitation of milking equipment prior to milking with PC and CC; strip cup testing of cows with PC; teat washing prior to milking with SCC; pre-milking teat disinfection with TBC and CC; post-dipping with TBC and SCC; and the alkaline-acid washing procedure of milking equipment with PIC and PC. The regression analysis explained the variation of bulk tank PC (- 0.47 log cfu/mL) due to the adoption of strip cup test (P = 0.036) and, by 0.366 log cfu/mL due to alkaline and acid washing of milking equipment (P = 0.036). Herringbone milking systems adopted on farms represented a change of - 0.11 log cfu/mL on the log SCC (P = 0.048). Findings may provide a guideline to prioritize efforts aimed at improving milk quality at the farm level in Brazil.

Detection and Enumeration of Streptococcus agalactiae from Bovine Milk Samples by Real-Time Polymerase Chain Reaction.

The aim of this study was to evaluate the use of real-time polymerase chain reaction (qPCR) combined with DNA extraction directly from composite milk and bulk tank samples for detection and enumeration of Streptococcus agalactiae (SAG) causing subclinical mastitis. Dilutions of sterile reconstituted skim milk inoculated with SAG ATCC 13813 were used to establish a standard curve (cfu/mL) for the qPCR assay targeting SAG. The analytical sensitivity and repeatability of the qPCR assay were determined. Bulk tank (BTM; n = 38) and composite milk samples (CM; n = 26) collected from lactating cows with positive isolation of SAG were submitted to the qPCR protocol and SAG plate counting, with results from both methods compared. Amplification of DNA was not possible in two out of 64 samples, indicating that qPCR was able to detect SAG in 96 and 97% of BTM and CM samples, respectively. The inter-assay coefficient of variation was <5%, showing that the technique had adequate repeatability. The qPCR protocol can be a high-throughput and rapid diagnostic assay to accurately detect SAG from BTM and CM samples compared with conventional microbiological culture method. However, the evaluated qPCR protocol is not accurate for enumerating SAG in milk samples, probably due to quantification of DNA of non-viable cells.

Staphylococcus aureus intramammary infection affects milk yield and SCC of dairy cows.

Staphylococcus aureus (S. aureus) is the most prevalent infectious microorganism affecting dairy cattle worldwide, and its pathogenic characteristics facilitate its spread in dairy herds. S. aureus intramammary infections (IMI) are mainly subclinical, and associated losses can exceed average herd losses where the pathogen is not isolated. However, the extent it affects milk composition at udder and quarter levels is still unknown, and cow composite milk losses may be underestimated due to the dilution effect. The aim of this study was to investigate the effects of S. aureus subclinical mastitis on mammary quarter milk yield and composition. In order to determine the effects of the pathogen on milk yield and composition at quarter level, a pairwise comparison of infected and non-infected mammary quarters (n = 28) from two dairy herds was carried out. Quarters were individually milked, and milk production and composition were assessed. S. aureus has increased somatic cell counts at quarter level; however, no effect of S. aureus IMI on milk lactose, fat, and protein contents was observed. Fat yield from infected quarters decreased, but losses due to the infection caused by S. aureus were not associated with quarter positioning in cows.

Pseudomonas spp. and P. fluorescens: population in refrigerated raw milk / Pseudomonas spp. e P. fluorescens: população em leite cru refrigerado

ABSTRACT: Raw milk samples were collected from cooling tanks (after they cooled for 48 h) in five dairy farms and the corresponding bulk tank (bulk milk transportation, BMT) when they arrived to the industry. Routine physical chemical analyzes and quantification of psychrotrophic ( Pseudomonas spp. and P. fluorescens ) and aerobic mesophilic (AM) populations were performed. Only relative density and titratable acidity values for samples of milk from three farms were in agreement to the quality parameters required by law. In the BMT, only the protein content has not reached the minimum value established by law, and counting was performed for AM (>105 colony forming units (CFU) mL-1) and psychrotrophic bacteria (2.8x106CFU mL-1). Pseudomonas spp. counting corresponded to 17.9% of the psychrotrophic population, and P. fluorescens was 3.4% of Pseudomonas spp . count. In milk samples from dairy farms, counts were variable for AM (3.4x105 to 3.7 x107CFU mL-1), psychrotrophic (4.0x104 to 3.1x106CFU mL-1), Pseudomonas spp. (2.3x104 to 1.8x105CFU mL-1), and P. fluorescens (62 to 8.4x103CFU mL-1). For the populations studied, no statistical difference (P>0.05) was observed between counts reported in milk samples collected in dairy farms (cooling tanks) and BMT. Therefore, the genera Pseudomonas spp. and P. fluorescens were not the most frequent psychrotrophic bacteria in this studied milk transportation line.

RESUMO: Amostras de leite foram coletadas de tanques de refrigeração (após 48h de refrigeração) em cinco fazendas de produção e do respectivo caminhão tanque (leite de conjunto, LC) ao chegar à indústria beneficiadora. Análises físico químicas de rotina e quantificação das populações de bactérias psicrotróficas ( Pseudomonas spp. e P. fluorescens ) e aeróbios mesófilos (AM) foram realizadas. Apenas os valores de densidade relativa e acidez titulável de amostras de leite de três fazendas estavam de acordo com a legislação. No LC, apenas o teor de proteína não atingiu o valor mínimo estabelecido por lei, e a contagem foi realizada para AM (>105 unidades formadoras de colônias (UFC) mL-1) e psicrotróficos (2,8x106UFC mL-1). A contagem de Pseudomonas spp. correspondeu a 17,9% da população de psicrotróficos, e 3,4% da contagem de Pseudomonas spp. eram da espécie P. fluorescens . Nas amostras de leite das fazendas de produtoras, as contagens foram variáveis para AM (3,4x105a 3,7x107UFC mL-1), psicrotróficos (4,0x104 a 3,1x106UFC mL-1), Pseudomonas spp. (2,3x104 a 1,8x105UFC mL-1) e P. fluorescens (62 a 8,4x103UFC mL-1). Para as populações estudadas, nenhuma diferença estatística (P>0,05) foi observada entre as contagens encontradas nas amostras de leite coletadas nas fazendas (tanques de resfriamento) e do LC. Portanto, o gênero Pseudomonas spp. e a espécie P. fluorescens não foram os psicrotróficos mais frequentes nesta linha de transporte de leite estudada.

Prediction of bovine milk true protein content by mid-infrared spectroscopy / Estimativa do teor de proteína verdadeira do leite bovino por espectroscopia na região do infravermelho médio

The aim of this study was to estimate the concentration of milk true protein (TP) by mid-infrared absorbance method (MIR) in samples from bulk tank of dairy herds, and to determine the correlation between the results of TP of milk determined by Kjeldahl and MIR. Forty nine dairy herds were selected (17 Holstein, 6 Jersey and 26 Girolando) for monthly collections of samples from bulk tanks during the period of one year (284 samples). Fat, lactose, crude protein and total solids were firstly determined by MIR, and then analyzed for total and true protein by Kjeldahl method. The regression equation to estimate TP contents based on MIR crude protein determination was as follows: TP=0.0021+(1.0104xCP), where: TP is the content of true protein, CP is the crude protein content determined by the MIR method, and 0.0155 is the model error term.

O objetivo deste estudo foi estimar o teor de proteína verdadeira (PV) do leite por meio de metodologia de espectroscopia na região do infravermelho médio (IVM), em amostras de tanque de rebanhos leiteiros comerciais, e determinar a correlação entre os resultados de proteína verdadeira do leite determinados pelo método de Kjeldahl e por IVM. Foram selecionados 49 rebanhos leiteiros (17 da raça Holandesa, seis da raça Jersey e 26 da raça Girolando) para coletas mensais de amostras de leite de tanque durante o período de um ano, totalizando 284 amostras analisadas. As amostras de leite foram analisadas inicialmente em relação aos teores de gordura, lactose, proteína bruta e sólidos totais por IVM, sendo em seguida analisadas quanto ao teor de PB e PV pelo método de Kjeldahl. A equação de regressão para estimativa do teor de PV com base nos teores de proteína bruta foi a seguinte: PV=0,0021+(1,0104xPB); em que: PV é o teor de proteína verdadeira estimado; PB é o teor de proteína bruta pelo método IVM e 0,0155 é o erro apresentado pelo modelo.

Efeito da remoção de células somáticas pela microfiltração sobre a lipólise do leite / Effect of somatic cell removal by microfiltration on the lipolysis of milk

O objetivo do presente estudo foi avaliar o efeito da retirada mecânicadas células somáticas do leite cru sobre a taxa de lipólise durante o armazenamento refrigerado do leite pasteurizado. O delineamento experimental utilizado foi totalmente casualizado, com três repetições e arranjo fatorial de tratamentos 2 X 2 X 2, constituídos por dois nível de gordura do leite (desnatado e integral), dois níveis de contagem de células somáticas (CCS baixa - CCSB e CCS alta - CCSA), e pela aplicação ou não da microfiltração ao leite. Três lotes de leite cru CCSB (75.000 cél./mL) e CCSA (1.150.000 cél./mL) foram obtidos de vacas selecionadas e submetidos ao desnate centrífugo, à microfiltração em sistema a vácuo, sendo em seguida pasteurizados e armazenados por 21 dias sob refrigeração a 6ºC. Foram realizadas medidas repetidas no tempo, as quais corresponderam aos dias de coleta do leite pasteurizado durante o período de armazenamento (1, 7, 14 e 21). A microfiltração associada ao desnate foram eficazes na remoção das células somáticas do leite, com reduções de 92,5 e 99,5% para o leite CCSB e CCSA, respectivamente. A lipólise do leite aumentou em função do tempo de armazenamento e foi maior para o leite microfiltrado, contudo não sofreu influência da CCS. Independentemente da CCS, ocorreu aumento da lipólise do leite pasteurizado durante o período de armazenamento.

The objective of this study was to evaluate the effects of raw milk somatic cell removal by microfiltration on lipolysis of pasteurized milk during refrigerated storage. A completely randomized design was used, with 3 repetitions and a 2 X 2 X 2 factorial arrangement of treatments as follow: milk fat level (skimmed and whole milk), two different levels of somatic cell counts - low somatic cell count (LSCC) and high somatic cell count (HSCC) - and, use of microfiltration ornot. LSCC raw milk - 75,000 cells/ml - and HSCC raw milk - 1,150,000 cells/ml - were obtained from selected cows, skimmed and submitted to vacuum microfiltration. Milk from all treatments was pasteurized and kept refrigerated at 6ºC for 21 days. Repeated measures during storage time were taken from pasteurized milk at days 1, 7, 14 and 21. The application of milk microfiltration was efficient on somatic cell removal, with reduction of 92,5 and 99,5% for LSCC and HSCC,repectively. Lipolysis of milk was increased during storage period and was higher for milk submitted to icrofiltration, however no effect of SCC was observed. Lipolysis in pasteurized milk increased independently of SCC, during its refrigerated storage period.

Remoção de células somáticas pela microfiltração não afeta a composição e a proteólise do leite / Somatic cell removal by microfiltration does not affect composition and proteolysis of milk

O objetivo do presente estudo foi avaliar os efeitos da retirada mecânica das células somáticas do leite cru sobre a composição e a proteólise durante o armazenamento refrigerado do leite pasteurizado. O delineamento experimental utilizado foi o de blocos generalizados ao acaso, no qual foram considerados como blocos as repetições (n=3) e o nível de gordura do leite (desnatado e integral). Utilizou-se um arranjo fatorial de tratamento do tipo 2 x 2, constituído por: dois níveis de contagem de células somáticas - CCS (baixa e alta CCS) e pela aplicação ou não da microfiltração ao leite. Foram realizadas, ainda, medidas repetidas no tempo, as quais corresponderam aos dias de coleta do leite pasteurizado durante o período de armazenamento (1, 7, 14 e 21 dias). Os lotes de leite cru de alta (1.000.000cél. mL-1) e baixa (100.000cél. mL-1) CCS foram submetidos ao desnate centrífugo, à microfiltração em sistema a vácuo e, em seguida, os lotes de todos os tratamentos foram pasteurizados e armazenados por 21 dias sob refrigeração a 6°C. Não foi identificado efeito da microfiltração sobre a proteólise do leite, indicando que este tratamento não reduziu a taxa de proteólise do leite de alta CCS durante o período de armazenamento. Foi observado efeito significativo do tempo de armazenamento sobre a proteólise, indicando a manutenção de atividade proteolítica mesmo após a pasteurização do leite. Pode-se concluir que o leite com alta contagem de células somáticas apresenta maior taxa de proteólise durante o período de armazenamento que o leite de baixa contagem de células somáticas. A microfiltração como processo de retirada mecânica das células somáticas do leite não reduz a proteólise do leite durante o armazenamento.

This study was aimed at evaluating the effects of raw milk somatic cell removal by microfiltration on the composition and proteolysis during refrigerated storage of pasturized milk. A completely randomized block design was used, in which repetitions (n=3) and milk fat level (skimmed and whole milks) were considered as blocks. A 2 X 2 factorial arrangement of treatments was used: milks with two different levels of somatic cell counts - low somatic cell count (LSCC) and high somatic cell count (HSCC) - and, microfiltration or not of milk. Repeated measures during storage time were taken from pasteurized milk at days 1, 7, 14 and 21. LSCC raw milk - 100,000cells mL-1 - and HSCC raw milk - 1,000,000cells mL-1 - were obtained from selected cows, skimmed and submitted to vacuum microfiltration. Milk was pasteurized and kept refrigerated at 6°C for 21 days. The application of milk microfiltration was efficient on somatic cell removal; however microfiltration had no effect on milk proteolysis which means the treatment did not reduce HSCC milk proteolysis rate during refrigerated storage. Significant effect of storage period on proteolysis was observed indicating that proteolytic activity remained despite milk pasteurization. HSCC milk proteolytic activity was 1,42 times higher than in LSCC milk, during the 21-day of refrigerated storage period. Based on the results of the study, HSCC milk shows a higher proteolytic activity than LSCC milk, during the 6°C-21 day storage period. Microfiltration, as a somatic cell removal process had no effect on decreasing proteolytic activity of pasteurized milk during the refrigerated storage period.