UHT Cream Research Articles

Antimicrobial activity, environmental sensitivity, mechanism of action, and food application of αs165-181 peptide

αs165-181 is a peptide derived from αs2-casein of ovine milk. Herein, we report the antimicrobial activity and mechanism, and food application of the peptide. αs165-181 showed antimicrobial activity against Escherichia coli, Staphylococcus aureus, Bacillus subtilis, Listeria monocytogenes, Bacillus cereus, and Salmonella enterica serovar Enteritidis in a dose-dependent manner. The minimum inhibitory concentration of the peptide was 3.9 mg/ml for E. coli and 7.8 mg/ml for the other bacteria. The peptide did not show antimicrobial activity against Lactobacillus plantarum up to 3.9 mg/ml concentration. The minimum bactericidal concentration of αs165-181 peptide was 7.8 mg/ml for E. coli, S. aureus, L. monocytogenes, and B. cereus. The peptide was sensitive to monovalent and divalent cations, pH, and high temperatures. Transmission electron microscopy, cytoplasmic β-galactosidase leakage, and DNA electrophoresis analyses showed that αs165-181 peptide affects bacteria by damaging cell membrane and binding to the genomic DNA. When αs165-181 peptide was applied to minced beef or UHT cream, the antimicrobial activity (7.8 mg/g) was almost the same as or even better than nisin (0.5 mg/g). This study helps understand the antimicrobial mode of action of αs165-181 peptide and develop strategies for application in food products.

Metabolic effects in mice of cream formulation: Addition of both thickener and emulsifier does not alter lipid metabolism but modulates mucus cells and intestinal endoplasmic reticulum stress

Additives stabilize or improve the organoleptic or functional properties (or both) of many dairy products including whipping cream. Their influence on the metabolic effect of dairy cream is scarcely known. We tested the hypothesis that added emulsifier (lactic acid esters of mono- and diglycerides; MAG/DAG), thickener (carrageenan, CGN), or both, could modify the metabolic effect, notably in the intestine and liver. Nine-week-old male C57Bl/6J mice were fed UHT cream (indirect treatment) mixed with nonlipidic powder (final: 13% milkfat) for 1 or 4 wk. We compared creams (1) without additive (Ctl), (2) with thickener (Th), 0.02% of κ-CGN, and (3) with both thickener and emulsifier, 0.1% of MAG/DAG esters (Th/Em). We analyzed plasma parameters, intestine, and liver. Fasting glycemia, insulinemia, triglyceridemia, nonesterified fatty acids, body weight gain, and liver weight did not differ among groups. After 1 wk, Th/Em had higher expression in the duodenum of some of the genes involved in (1) intestinal lipid absorption and (2) tight junction proteins versus Ctl and Th. After 4 wk, mucus cell number in the small intestine was higher in Th/Em versus Ctl and Th. Genes involved in endoplasmic reticulum (ER) stress in the duodenum were more expressed in Th/Em after 1 wk. After 4 wk, in the colon, a higher expression of ER stress genes was observed for Th versus Th/Em and Ctl. Liver damage score was not altered by additives. Adding both CGN (0.02%) and MAG/DAG esters (0.1%) in dairy cream did not result in deleterious outcomes in mice after 4 wk regarding lipid metabolism, intestinal permeability, and liver disorders. The longer term effect of intestinal ER stress modulation deserves further investigation.

Determinação do extrato seco de leite fermentado, leite UHT e creme de leite: avaliação de uma metodologia simplificada

http://dx.doi.org/10.5007/1807-0221.2016v13n24p83O extrato seco do leite e de produtos lácteos é uma fração de extrema importância na qualidade e no indicativo nutricional desses alimentos. No caso do leite, o seu valor nutricional e a capacidade de gerar produtos como queijo, iogurte e manteiga são inerentes à fração seca. Objetivou-se neste trabalho avaliar a cinética de secagem e comparar o desempenho das diferentes metodologias analíticas na determinação do extrato seco total em leite UHT integral, creme de leite e leite fermentado. O delineamento experimental utilizado foi o inteiramente casualizado (DIC), com três tratamentos e três repetições para cada um dos produtos. Cada análise foi feita em duplicata. As metodologias usadas para o leite UHT foram AOAC (1998), Pereira et al. (2001) e placa de Petri sem areia purificada e sem pérola de vidro. A forma de secagem foi em estufa a 102 ± 2 oC. Na avaliação dos resultados, foi feita análise de variância (ANOVA) e o teste de Tukey para resultados significativos, ao nível de 5% de probabilidade e a construção de curvas de secagem. As diferenças entre as metodologias não foram significativas indicando que qualquer uma delas pode ser utilizada com segurança na determinação do extrato seco total dos produtos utilizados. O método da placa de Petri mostrou-se mais eficiente na velocidade de secagem, mais barato e simples de ser executado para pesquisadores que buscam alternativas em análises laboratorais.

Transient development of whipped cream properties

Commercially available UHT cream was tempered at 4 °C for 24 h and whipped for different times: 3, 6, 9 and 12 min. The following properties of cream were measured: rheological and interfacial properties, overrun and size distribution of air bubbles. The whipping process changes the properties of cream, which exhibits viscoelastic behaviour with a high influence of elastic component. The air bubbles incorporated during the process result in forming stronger foam containing smaller bubbles, and also give a higher overrun. These changes are observed around 9 min of whipping, when the amount of air is sufficient to create a stable structure. Further whipping reduces the overrun and the foam partly collapses; this may be caused by aggregation of fat droplets.

PROPRIEDADES TERMOFÍSICAS DE SOLUÇÕES MODELO SIMILARES A CREME DE LEITE

A demanda de creme de leite UHT tem aumentado significativamente. Diversas empresas diversificaram e aumentaram sua producao, visto que o consumidor, cada vez mais exigente, almeja cremes com ampla faixa de teor de gordura. O objetivo do presente trabalho foi determinar a densidade, viscosidade aparente e difusividade termica, de solucoes modelo similares a creme de leite, na faixa de temperatura de 30 a 70°C, estudando a influencia do teor de gordura e da temperatura nas propriedades fisicas dos produtos. O delineamento estatistico aplicado foi o planejamento 3X5, usando niveis de teor de gordura e temperatura fixos em 15%, 25% e 35%; 30°C, 40°C, 50°C, 60°C e 70°C, respectivamente (STATISTICA 6.0). Manteve-se constante a quantidade de carboidrato e de proteina, ambos em 3%. A densidade foi determinada pelo metodo de deslocamento de fluidos em picnometro; a difusividade termica com base no metodo de Dickerson e a viscosidade aparente foi determinada em reometro Rheotest 2.1. Os resultados de cada propriedade foram analisados atraves de metodo de superficie de resposta. No caso destas propriedades, os dados obtidos apresentaram resultados significativos, indicando que o modelo representou de forma confiavel a variacao destas propriedades com a variacao da gordura (%) e da temperatura (°C).

Oxidation behaviour of vanillin in dairy products

The stability of vanillin in dairy products was investigated by means of highperformance liquid chromatography. While vanillin was oxidised to vanillic acid in fresh and pasteurised milk, it was stable in all other milk products investigated (UHT milk, pasteurised and UHT cream, yoghurt, curd and butter). The oxidation of vanillin to vanillic acid was shown to be pH-dependent. The relatively thermolabile enzyme xanthine oxidase was shown to be partly responsible for the formation of vanillic acid. However, peroxidase, which is also present in dairy products, did not lead to vanillic acid. Oxidation to the dimeric product, divanillin, occurred in the presence of peroxidase and hydrogen peroxide. The oxidation rate of synthetic vanillin to vanillic acid was very similar to that of vanillin from natural vanilla extracts or vanilla capsules. Both were shown to be stable in dairy products for subvention, such as butter and cream.

Lactulose, monosaccharides and undenatured serum protein contents in commercial UHT creams and their usefulness for thermal treatment assessment

Fifteen UHT cream samples with different fat levels (ranging from 10% to 35%) were analysed for free carbohydrates (lactose, lactulose, glucose, galactose and myoinositol) and undenaturated whey proteins using gas chromatography and high-performance liquid chromatography, respectively. Lactulose concentrations ranged from 7 to 177 mg per 100 ml, α-lactalbumin from 5.1 to 61.6 mg per 100 ml and β-lactoglobulin from 1.0 to 64.0 mg per 100 ml. These values were similar to those reported for UHT milks. The ratio β-lactoglobulin/lactulose was found to be significantly higher than that reported for UHT milk.

Fat lipolyzed with a commercial lipase for the production of blue cheese flavour

The lipolytic activity and potential cheese flavour-producing ability of six commercial enzymes were determined on two fat substrates, UHT cream and butter oil. It was observed that UHT cream was the better substrate for the production of the free fatty acids (FFA) necessary for the preparation of flavour cheese. A lipolytic enzyme from Penicillium roqueforti (Amano Pharmaceutical) was selected for the production of blue cheese flavour. The growth of P. roqueforti was inhibited by FFA present in lipolyzed cream.

Heat resistance of ascospores of Byssochlamys nivea in milk and cream

Byssochlamys nivea strains of rather varying origin used for heat inactivation experiments were cultured for 28 days at 30°C on malt extract agar, since under these conditions the highest degree of heat resistance of the ascospores was observed. Inactivation was performed in steel capillary tubes to obtain reproducible results under experimental conditions comparable to those prevailing in practice. An inactivation temperature of 92°C proved to be most practical. Decimal reduction times for the individual strains at this temperature in Ringer's solution varied between 1.3 and 2.4 s. In the temperature range studied, inactivation of ascospores in UHT milk (1.5% w/w fat content) and cream (10% w/w fat content) has not been found to differ significantly from that in Ringer's solution. Homogenization of milk as applied in practice did not affect heat inactivation of ascospores. Assuming the most unfavorable conditions (50 ascospores/l and using the most heat-resistant strain) the following relations between the level of infected 500 g packages were calculated: 1 of 10 6 packs infected; 24 s at 92°C; 1 of 10 3 packs infected; 16.5 s at 92°C; 1 of 10 2 packs infected, 14 s at 92°C.

Case 124/81 Commission v. United Kingdom, France intervening (UHT milk and cream). Judgment of 8 February 1983. Plenary session. Judge rapporteur: Y.

Case 124/81 <i>Commission</i> v. <i>United Kingdom</i>, France intervening (UHT milk and cream). Judgment of 8 February 1983. Plenary session. Judge rapporteur: Y.

LIPID OXIDATION AS A SOURCE OF OFF‐FLAVOUR DEVELOPMENT DURING THE STORAGE OF DAIRY PRODUCTS

SummaryThe suggested mechanism for the formation of oct‐l‐en‐3‐one and malonaldehyde, two lipid oxidation products, is diagrammatically summarized. The thiobarbituric acid (TBA) and peroxide methods are critically evaluated as standard chemical indices of oxidative rancidity in dairy products. Some recent results on the effect of copper contamination, light exposure and storage temperatures on the oxidative stability of butter, cheese and UHT cream are discussed.