No abstract

The work described in this Research Communication concerns the production of Dulce de leche (DL), that is a traditional product from South America obtained by concentration. Maillard reaction (MR) products are mainly responsible for the formation of color and flavor in this product. Lactose-hydrolyzed products have been developed to supply consumer demand, but this hydrolysis may affect the flavor, color, taste, texture and even some nutritional aspects of the product. We studied the influence of different levels of lactose-hydrolysis, sucrose addition and initial pH on the development of MR, appraised by the determination of 5-hydroxymethylfurfural (HMF). A process simulator with multi-monitoring system was used to produce 15 DL. Box-Behnken 33 experimental design was applied for the three factors: pH, lactose-hydrolysis level and sucrose concentration. Lipids, protein, ashes, carbohydrates, water activity, dissolved solids, colorimetric analysis and HMF (free and total) are among the physicochemical attributes and MR indicators analyzed in this work. The products showed significant differences in composition but all the values were in agreement with the literature. Moreover, higher levels of lactose hydrolysis and higher pH presented a direct relation with the development of MR, observed by an increase in coloration (lower luminosity) and more formation of HMF, both free and total. The present study expands the knowledge about DL spread made of lactose-hydrolyzed milk, allowing the food industries to produce a lactose free DL with nutritional and sensory characteristics closer to the traditional product.

O consumo de pizzas prontas aumentou nos últimos anos dado à praticidade do produto e ao baixo custo, sabor agradável e valor nutritivo. Porém, esse produto sofre intensa manipulação durante o seu processamento, contribuindo para sua contaminação, diminuindo a qualidade e aumentando os riscos de doenças veiculadas por esse alimento. Aliado à necessidade de produtos práticos e convenientes, o consumidor demanda alimentos cada vez mais seguros, despertando o interesse pelo uso de conservantes naturais. Dentre eles, o óleo essencial de orégano apresenta ação antimicrobiana, sendo essa especiaria utilizada na culinária de vários países. O objetivo deste trabalho foi o desenvolvimento de filme de base celulósica, incorporado com óleo essencial de orégano para conservação de pizza pronta refrigerada. Esse óleo incorporado ao filme nas concentrações de 25 e 50% p/p apresentou efeito inibitório in vitro para Penicillium spp. e Staphylococcus aureus. Quando aplicado em pizza observou-se diminuição dos compostos ρ-cimeno e γ-terpineno e consequente aumento da concentração de timol e carvacrol, mas provavelmente em quantidade insuficiente para o efeito inibitório dos microrganismos. Com relação à resistência mecânica, os filmes incorporados com 25 e 50% de óleo tiveram sua resistência diminuída, tendo a tenacidade do filme de 50% aumentada com relação ao controle (0%). O uso de filme incorporado com o óleo de orégano desperta grande interesse na aplicação em pizzas, uma vez que o orégano já é um ingrediente do produto, portanto não compromete o sabor e odor da pizza.

The objective of this work was to evaluate the impact of changes during membrane filtration on the heat stability of milk protein concentrates. Dairy protein concentrates have been widely employed in high protein drinks formulations and their stability to heat treatment is critical to ensure quality of the final product. Pasteurized milk was concentrated three-fold by membrane filtration, and the ionic composition was modified by addition of water or permeate from filtration (diafiltration). Diafiltration with water did not affect the apparent diameter of the casein micelles, but had a positive effect on heat coagulation time (HCT), which was significantly longer (50 min), compared to the non diafiltered concentrates (about 30 min). UHT treatments increased the particle size of the casein micelles, as well as the turbidity of retentates. Differences between samples with and without diafiltration were confirmed throughout further analysis of the protein composition of the unsedimentable fraction, highlighting the importance of soluble protein composition on the processing functionality of milk concentrates.

Membrane filtration technologies are widespread unit operations in the dairy industry, often employed to obtain ingredients with tailored processing functionalities. The objective of this work was to better understand the effect of partial removal of whey proteins by microfiltration (MF) on the heat stability of the fresh concentrates. The micellar casein concentrates were compared with control concentrates obtained using ultrafiltration (UF). Pasteurized milk was microfiltered (80 kDa polysulfone membrane) or ultrafiltered (30 kDa cellulose membrane) without diafiltration (i.e., no addition of water) to 2× and 4× concentration, based on volume reduction. The final concentrates showed no differences in pH, casein micelle size, or mineral concentration in the serum phase. The micellar casein retentates (obtained by MF) showed a 20 and 40% decrease in whey protein concentration compared with the corresponding UF milk protein concentrates for 2× and 4× concentration, respectively. The heat coagulation time decreased with increasing protein concentration, regardless of the treatment; however, MF retentates showed a higher thermal stability than the corresponding UF controls. The average diameter for casein micelles increased after heating in UF but not MF concentrates. The turbidity (measured by light scattering) increased after heating, but to a higher extent for UF retentates than for MF retentates at the same protein concentration. It was concluded that the reduced amount of whey protein in the MF retentates caused a significant increase in the heat stability compared with the corresponding UF retentates. This difference was not due to ionic composition differences or pH, but to the type and amount of complexes formed in the serum phase.

Besides increasing shelf life of fluid milk, milk powder has physical and functional properties that allow it to be used as ingredient. The rehydration process is complex and happens in four steps: wettability, sinkability, dispersibility and solubility. Works have been conducted aiming at the development of an easier, more convenient and reproducible method to evaluate the dissolution properties of dairy powders. Therefore, the aim of this work was to evaluate dispersibility and solubility through particle size distribution in order to establish a new rehydration index for whole milk powder. The particle size distribution and morphological characteristics of seven samples of milk powder (from A to G) were analyzed. Samples F and C differed from the others which formed a similar group. Principal component analysis divided the samples into three different groups, allowing the indication of an efficient rehydration index to determine the powders dispersability.

No abstract

The aim of this study was to evaluate the effects of bulk tank milk (BTM), WM, and PWM on the intake, ruminal parameters, blood parameters, health, and performance of dairy calves. Forty-five male crossbred dairy calves (Gyr × Holstein) were used. On their fourth day of age, animals were grouped according to body weight, serum protein levels, and genetic composition. Three treatments were assessed: BTM (n = 15), WM from cows in antibiotic treatment (n = 15), and PWM via high-temperature, short-time pasteurization (72–74 °C for 16 s) (n = 15). During the experimental period (from 4 to 60 d of age), animals were fed 6 L of milk/d, divided into two equal meals. Water and concentrate were provided ad libitum. Daily measurements were made for milk, concentrate, and water intakes, as well as for fecal and respiratory scores. Rumen fluid and blood were sampled weekly. The following parameters were evaluated: volatile fatty acids (VFAs), pH and ammonia-N in rumen fluid, and β-hydroxybutyrate (BHB) and glucose in blood. Animals were weighed at birth, 4 d of age, and weekly up to 60 d of age. At the end of the experimental period (60 ± 1 d), all animals were euthanized for pulmonary evaluation. The randomized complete design with an interaction between treatment and week was the experimental method of choice for testing the hypothesis of the treatment’s effect on all evaluated outcomes. Animals in the BTM treatment had higher milk dry matter intake (DMI), followed by WM and PWM calves. Concentrate DMI was lower for BTM in comparison to WM and PWM calves. However, total DMI showed no significant differences between treatments. The rumen fluid from calves receiving PWM had higher concentrations of acetate and propionate than that of BTM and WM animals. No differences were observed between treatments for blood glucose and BHB concentrations. Health parameters (fecal and respiratory scores) and pneumonia occurrence showed no significant difference between treatments. No differences were observed for average daily gain (ADG) or body growth. Feeding WM and PWM did not show significant negative effects on the intake, ruminal parameters, blood parameters, health, or performance of dairy calves.