L.M. Fonseca

Homogenization and lipase treatment of milk and resulting methyl ketone generation in blue cheese.

A specific range of methyl ketones contribute to the distinctive flavor of traditional blue cheeses. These ketones are metabolites of lipid metabolism by Penicillium mold added to cheese for this purpose. Two processes, namely, the homogenization of milk fat and the addition of exogenous lipase enzymes, are traditionally applied measures to control the formation of methyl ketones in blue cheese. There exists little scientific validation of the actual effects of these treatments on methyl ketone development. The present study evaluated the effects of milk fat homogenization and lipase treatments on methyl ketone and free fatty acid development using sensory methods and the comparison of selected volatile quantities using gas chromatography. Initial work was conducted using a blue cheese system model; subsequent work was conducted with manufactured blue cheese. In general, there were modest effects of homogenization and lipase treatments on free fatty acid (FFA) and methyl ketone concentrations in blue cheese. Blue cheese treatments involving Penicillium roqueforti lipase with homogenized milk yielded higher FFA and methyl ketone levels, for example, a ∼20-fold increase for hexanoic acid and a 3-fold increase in 2-pentanone.

Milk quality according to the daily range in farm production in the Mesoregion Central Mineira and Oeste of Minas Gerais regions, Brazil

The objective of this work was to characterize milk production from the Central Mineira and Oeste Mesoregions regions in Minas Gerais State, Brazil, according to quality parameters such as somatic cell count, total bacteria count, and composition for specific production ranges. Average results for milk fat, protein, total and nonfat solids were compliant with Brazilian legal requirements (IN-62/2011) in all the production ranges selected. Average somatic cell counts (SCC) complied with the legal requirements of 600,000 cells/mL, except for the range with a daily production above 1,000 liters. However, average maximum values of 400,000 cells/mL are recommended for good milk quality. Total bacterial count was the most critical quality factor, with the highest values found in breeds with milk production above 500 liters per day.

Detection of cheese whey in raw milk preserved with bronopol® through high performance liquid chromatography

High performance liquid chromatography was used in order to detect cheese whey in samples of raw milk preserved with Bronopol®. Six samples were collected and divided in 45 aliquots of 40mL. From these, 15 were used as control and stored frozen, 15 were added with Bronopol® and stored at 7oC, and the other 15 were added with Bronopol® and stored at 30oC. In all groups, five levels of cheese whey addition (0, 2, 5, 10, and 20%) were tested. The samples were submitted to high performance liquid chromatography on the 2nd, 4th, and 8th days of storage. A completely random design was used, following the factorial scheme (5x3x3) and the results were compared through the non-parametric Kruskal-Wallis test. There was no difference among the treatments (P>0.05), which allows the conclusion that raw milk preserved with Bronopol® may be used for the determination of cheese whey addition in milk through high performance liquid chromatography.

Composição centesimal e aceitação de lingüiça elaborada com reduzido teor de gordura e adicionada de concentrados protéicos de soro de leite

The objective of the research was to evaluate the composition and acceptance of pork sausages manufactured with whey protein concentrate (WPC) or with protein concentrate containing high level of b-lactoglobulin (hereof called b-lactoglobulin) as fat substitutes. Seven treatments were established, a control containing 20% of fat, and six containing different levels of WPC or b-lactoglobulin addition (three treatments containing 10% of fat and 0.2%, 0.5% or 1.0% of WPC, and three treatments containing 10% of fat and 0.1%, 0.3% or 0.6% of b-lactoglobulin). Each treatment was repeated in five batches, and the samples of each batch was evaluated the first and seventh day after processing and storage at 4°C. The samples were analyzed for protein (g 100g-1), fat (g 100g-1), moisture content (g 100g-1), caloric value (kcal/g) and sensory analyses. The results of protein, fat and caloric value were different between the group control and the other treatments (P£0.05). Additionally, the moisture content and sensory analyses results showed that there was no difference (P>0.05) for the different treatments used in this experiment. The protein concentrates were efficient for the fat substitution in pork sausages, in the treatment levels used in the current experiment, complying with the specifications of the Brazilian legal requirements.

Influence of race and crossbreeding on casein micelles size

Casein (CN) micelles are colloidal aggregates of protein dispersed in milk, the importance of which in the dairy industry is related to functionality and yield in dairy products. The objective of this work was to investigate the correlation of milk CN micelles diameter from Holstein and Zebu crossbreds with milk composition (protein, fat, lactose, total and nonfat solids and milk urea nitrogen), somatic cell count (SCC), age, lactation stage and production. Average casein micelles diameters of milk samples obtained from 200 cows were measured using photon correlation spectroscopy and multiple regression analysis was used to find relationship between variables. CN micelle diameter, SCC and nonfat solids were different between animals with different Holstein crossbreed ratios, which suggests influence of genetic factors, mammary gland health and milk composition. Overall, results indicate the potential use of CN micelle diameter as a tool to select animals to produce milk more suitable to cheese production.

Bioactive amines in mozzarella cheese from milk with varying somatic cell counts

The influence of somatic cells counts (SCC) in milk on bioactive amines in Mozzarella cheese was investigated. High SCC milk had lower lactose and higher pH compared to low and medium SCC. Low spermine levels were found in milk irrespective of SCC. The cheeses had similar characteristics, but the extension and depth of proteolysis increased with SCC. Cheese from all SCC categories contained spermine; whereas tyramine and tryptamine were only detected in cheese from high SCC milk. During 60-days refrigerated storage, significant positive effects were observed between SCC and proteolysis, storage time and pH and storage time and proteolysis. There was a significant positive effect of storage time on spermine and serotonin levels. Only cheese from high SCC milk showed significantly higher serotonin levels. Tyramine and tryptamine were found in cheese from high SCC milk.

Desempenho de vacas em lactação alimentadas com dietas contendo torta de macaúba

We evaluated nutrient intake, production and composition of milk from Holstein cows fed feedlot diets with different inclusion levels of macauba meal. Eight animals were divided into two 4x4 latin square designs, four treatments, 0, 100, 200 and 300g kg-1 macauba meal in the dry matter diet, and four experimental periods of 21 days, 14 adaptation and seven evaluation The addition of increasing levels of macauba meal diet alter the intake of dry matter, organic matter, crude protein, ether extract, neutral detergent fiber, non-fiber carbohydrates, production and concentration of lactose, nonfat dry and total solids in milk, as well as the feed efficiency and digestibility of dry matter. Moreover, there was no difference in the levels of milk fat. The addition of macauba meal up to 300g kg-1 diet compromised the consumption and production performance of animals.

A Lactobacillus rhamnosus strain induces protection in different sites after Salmonella enterica subsp. enterica serovar Typhimurium challenge in gnotobiotic and conventional mice

The ability of a Lactobacillus rhamnosus strain isolated from a healthy breast-fed human newborn to reduce the pathological consequences for the host due to an experimental oral infection with Salmonella enterica subsp. enterica serov. Typhimurium in vivo was determined using gnotobiotic and conventional mice. Conventional mice received 0.1mL probiotic milk (8.0 log colony-forming unit) daily for 10 days before the oral pathogenic challenge (5.0 log colony-forming unit). Then probiotic treatment was continued until the end of the experiment. Probiotic treatment in germ-free mice consisted of a single dose of the probiotic milk at the beginning of the experiment and a challenge with S. Typhimurium 10 days later (3.0 log colony-forming unit). A protective effect was observed in both gnotobiotic and conventional animals in terms of histopathologic and morphometric data, but in different anatomical sites. This protection was observed in liver and intestines, respectively, for gnotobiotic and conventional mice. However, S. Typhimurium populations were similar in the feces of both treated and control gnotobiotic mice. We conclude that a protective effect of L. rhamnosus against experimental S. Typhimurium was observed. This protection was not due to the reduction of the population of pathogenic bacteria in the intestine.

Application of Scharer's quantitative method for the determination of residual alkaline phosphatase activity in standard Minas

Milk pasteurization is a critical issue in the dairy industry, and failures in this process can affect final product safety. Scharers enzymatic method is still traditionally used to verify pasteurization efficiency compliance, and it is based on screening for residual alkaline phosphatase in milk. Although several methods are used to quantify enzymatic activity to assess milk pasteurization efficiency, there is a small amount of published data regarding the use of these methods to quantify alkaline phosphatase in cheese. In this study, the Scharers modified method was used to determine the levels of residual alkaline phosphatase in standard minas cheese, before and after 20 days of ripening. The cheeses were made using raw or pasteurized milk with the addition of different concentrations of raw milk (0; 0.05%; 0.10%; 0.20%; and 0.50%). In the fresh cheese samples, the method showed a sensitivity of only 0.50% with the addition of raw milk to the pasteurized milk used to make cheese. In addition, levels of up 0.20% of raw milk in pasteurized milk, the concentrations of phenol was inferior to 1μg phenol/g of dairy product which is the preconized indicator value for adequate pasteurization.

Influence of somatic cell count and total bacterial counts of raw milk in cheese yield using small-scale methodology

The objectives of this study were to evaluate the influence of SCC and TBC of raw milk in cheese yield, using a reduced scale method, and to evaluate theoretical prediction of cheese yield. 270 samples of raw milk were split into three SCC levels (below 200,000; 200,000-750,000; above 750,000 SC/mL) and three TBC levels (below 100,000; 100,000-750,000; above 750,000 CFU/mL). Raw milk samples were submitted to compositional analysis (fat, protein, lactose, total solids and SNF content), SCC, TBC, freezing point and pH. The production of the small-scale cheese was conducted according to the method developed at Cornell University (Melilli et al., 2002). Cheese whey samples were submitted to compositional analysis (fat, total protein, true protein, lactose, total solids and SNF content) and SCC. The increase in the SCC of raw milk resulted in increased protein loss in cheese whey. High SCC (above 200,000 SC/mL) in milk samples was correlated to reduced dry matter yield. There was no effect of TBC in cheese yield in the experimental conditions used. There was a high correlation between the theoretical yield values and the yield values predicted by the small-scale method, indicating that this method is appropriate for cheese yield prediction.