Heat Treatment Of Milk Research Articles

Phytochemical-Rich Antioxidant Extracts of Vaccinium Vitis-idaea L. Leaves Inhibit the Formation of Toxic Maillard Reaction Products in Food Models.

Thermal treatment of proteinaceous foods generates heat-induced Maillard reaction substances including toxic advanced glycation end products (AGEs) and heterocyclic amines (HAs). It is known that plant phenolic compounds may influence Maillard reaction. This study investigated the impact of lingonberry leaf extracts on the formation of Nε -(carboxymethyl)lysine (CML) and Nε -(2-furoylmethyl)-L-lysine (furosine) in milk model system and HAs in meat-protein and meat model systems. In addition, lingonberry leaf extracts obtained by different solvents were characterized by radical scavenging, Folin-Ciocalteu assays and ultrahigh pressure liquid chromatography quadruple-time-of flight mass spectrometry (UPLC-qTOF-MS). Water extract (WE) stronger suppressed CML than furosine formation in milk model system: CML levels were reduced by nearly 40%. Moreover, quinic acid and catechin, which were abundant in WE, were effective in inhibiting CML and furosine formation. WE and acetone extract (AE) at 10 mg/mL significantly inhibited HAs formation in both model systems. However, higher suppressing effect on HAs formation showed AE, which had lower antioxidant capacity and total phenolic content values than WE. WE contained higher amounts of hydroxycinnamic acids, proanthocyanidins and flavonols, while AE was richer in flavan-3-ols and arbutin derivatives. It indicates that the composition of phenolics might be a major factor for explaining different effect of extracts from the same plant on HAs formation. In general, the results suggest that lingonberry leaves is a promising source of phytochemicals for inhibiting toxic Maillard reaction products and enriching foods with plant bioactive compounds. PRACTICAL APPLICATION: The increased consumption in processed foods has been linked with the increased risks of various diseases, while thermal food processing is required to develop flavor, insure safety, and extend shelf life. Therefore, developing effective technological means for inhibiting the formation of heat-induced toxic substances is an important task. This study showed a potential of lingonberry leaf extracts containing health beneficial phytochemicals to suppress the formation of toxic Maillard reaction products during heating of milk and meat.

The glycation level of milk protein strongly modulates post-prandial lysine availability in humans.

Industrial heat treatment of milk results in protein glycation. A high protein glycation level has been suggested to compromise the post-prandial rise in plasma amino acid availability following protein ingestion. In the present study, we assessed the impact of glycation level of milk protein on post-prandial plasma amino acid responses in humans. Fifteen healthy, young men (age 26 (SEM 1) years, BMI 24 (SEM 1) kg/m2) participated in this randomised cross-over study and ingested milk protein powder with protein glycation levels of 3, 20 and 50 % blocked lysine. On each trial day, arterialised blood samples were collected at regular intervals during a 6-h post-prandial period to assess plasma amino acid concentrations using ultra-performance liquid chromatography. Plasma essential amino acid (EAA) concentrations increased following milk protein ingestion, with the 20 and 50 % glycated milk proteins showing lower overall EAA responses compared with the 3 % glycated milk protein (161 (SEM 7) and 142 (SEM 7) v. 178 (SEM 9) mmol/l × 6 h, respectively; P ≤ 0·011). The lower post-prandial plasma amino acid responses were fully attributed to an attenuated post-prandial rise in circulating plasma lysine concentrations. Plasma lysine responses (incremental AUC) following ingestion of the 20 and 50 % glycated milk proteins were 35 (SEM 4) and 92 (SEM 2) % lower compared with the 3 % glycated milk protein (21·3 (SEM 1·4) and 2·8 (SEM 0·7) v. 33·3 (SEM 1·7) mmol/l × 6 h, respectively; P < 0·001). Milk protein glycation lowers post-prandial plasma lysine availability in humans. The lower post-prandial availability of lysine following ingestion of proteins with a high glycation level may compromise the anabolic properties of a protein source.

Thermally induced milk fouling: Survival of thermophilic spore formers and potential of contamination

Thermophilic spore formers are prevalent contaminants in powdered milk products. In this study, we investigated whether fouling layers formed during the heat treatment of milk have protective effects on entrapped thermophilic spores. First, we developed an experimental set-up to produce fouling layers and incorporate spores. It was possible to produce fouling layers that contained a constant count of thermophilic spores. Afterwards, the fouling layer was subjected to a cleaning procedure with alkaline, enzymatic, or acidic solutions and a peracetic acid disinfectant. No treatment could reduce the spore counts below 3 log in the contaminated fouling. Moreover, it was demonstrated that spores could transmit into the product stream in dairies. This was shown by submerging a contaminated fouling layer in UHT milk and measured the spore count afterwards. This work emphasises that milk fouling is a reservoir for thermophilic spores and additionally can protect entrapped spores against cleaning procedures.

Effects of ultrasonication on the physicochemical properties of milk fat globules of Bubalus bubalis (water buffalo) under processing conditions: A comparison with shear-homogenization

Abstract Ultrasonication has been widely studied in bovine milk but the effects of ultrasound (US) on the buffalo's milk fat globules (MFG) are not well known yet. In this study, buffalo's milk samples were ultrasonicated at 20 kHz and physicochemical properties were assessed under different processing conditions. Shear homogenization was performed with 1188 J/mL energy density for the comparison. Results show that ultrasonication reduced the average volume-weighted mean diameter (D[4,3]) of MFG by 93% and increased the surface area by a factor of 8.5 compared to the native counterparts. The zeta-potential (ZP) of MFG are increased by ultrasonication compared to fresh milk (−26.37 vs. −18.22 mV) indicating better stability. Changing the pH of ultrasonicated milk to the isoelectric pH (pI) reduced the zeta-potential (ZP) by −19.8 mV and increased the (D[4,3]) > 0.4 mm indicating the gelation. The size of milk particles increased up to 76–586 μm and the ZP was reduced by 3.1 mV with the increase of ionic strength from 50 to 200 mM. Heating of milk at 90 °C for 30 min increased D[4,3] in US homogenized milk by 22%. Both ultrasonication and shear-homogenization increased the free saturated fatty acids by 2.75–3 g/100 g fat compared to raw buffalo's milk. Ultrasonication increased the gel hardness by 98% compared and shear-homogenized milks. The results of this study indicate that the ultrasonication reduced the size of buffalo's MFG up to sub-micron level with superior stability while improving (P Industrial relevance Buffalo set-yoghurts made with unhomogenized milk exhibit higher syneresis and poor stability upon shear-induced breakdown, which are mainly due to the porous gel structure containing a large number of bigger fat globules. Under the large scale production, buffalo set-yoghurts are often fortified with dairy/non-dairy solids and stabilizers in order to prevent this problem. However, the use of some inexpensive, non-food grade alternatives are also reported in some parts of the world for the cottage or medium level production of buffalo yoghurts. In this work, it was shown that ultrasonication with the energy density of 1188 J/mL can be used to produce buffalo set-yoghurts with superior gel strength and therefore, can be used as an unconventional approach to improve the product quality.

Effect of heat treatment on bacteriostatic activity and protein profile of bovine whey proteins.

Bovine milk shows bacteriostatic activity mainly due to the presence of antibacterial proteins, like lactoferrin, lactoperoxidase and immunoglobulins. Heat treatment is applied to kill bacteria and thereby extend shelf life of dairy products. Such heat treatment may, however, impair the activity of native antibacterial proteins in milk. The aim of this study was to investigate bacteriostatic capacity and retention of antibacterial proteins in unheated and heated bovine milk. Skim milk samples were heated at 65 °C, 70 °C, 75 °C, 80 °C and 85 °C, for 30 min. Whey was isolated from the heat-treated skim milk and the bacteriostatic capacity of this whey was tested against Streptococcus thermophilus, Escherichia coli, Lactococcus lactis and Pseudomonas fluorescens. The proteomic profile of native whey was determined using LC-MS/MS-based proteomics. Results showed that the bacteriostatic activity of whey negatively correlated with intensity of heat treatment, which was also reflected in the reduced level of native antibacterial proteins. There is a significant difference between milk samples treated for 30 min at <75 °C and milk samples treated at ≥75 °C in both bacteriostatic capacity and native antibacterial proteins. Growth rates of Streptococcus thermophilus, Lactococcus lactis and Pseudomonas fluorescens were negatively correlated with retention of lactoferrin and lactoperoxidase. In conclusion, our study shows that the bacteriostatic capacity of whey decreases with increasing heating intensity, which is strongly correlated with the denaturation of antibacterial proteins. Bacteriostatic activity can be a biomarker for loss of function of antibacterial proteins, and can thereby be used as an indicator for the extent of heat processing of dairy products including antibacterial proteins in a mild heat treatment.

Thermodynamic studies on a solar assisted transcritical CO2 based tri-generation system with an ejector for dairy applications

A simple thermodynamic analysis is carried out on a novel solar energy based trigeneration system suitable for dairy applications. CO2 is considered as the working fluid for the entire system, in which an ejector replaces the throttle valve. The effect of important design and operating parameters on system performance is obtained. The performance is indicated in terms of overall COP, specific net power output and specific milk flow rate. The ranges of operating parameters are constrained to always produces a net positive power output. Results show that the milk heat exchanger influences the performance strongly. The specific net power output increases as the gas cooler pressure decreases and ambient temperature increases. However, the specific milk flow rate and overall COP are high at higher gas cooler pressure and lower ambient temperature. This shows the need for controlling the gas cooler pressure depending upon requirement of milk flow rate or power output. For the ranges of operating parameters considered, the overall COP of the trigeneration system is found to be around 0.8. Use of work recovery expander in place of ejector increases the overall COP by about 12%. However, when the ejector is replaced with a conventional throttle valve, then the net power output from the system becomes negative. It is expected that this preliminary study is useful in assessing the feasibility of the novel solar energy based CO2 system for dairy plants where there is a simultaneous need for heating, refrigeration and electrical power.

RP-HPLC determination of Furosine in fermented milk of different brands retailed in China

Heat treatment of milk is the most widely used processing technology in the dairy industry. It results in many chemical and biochemical changes in milk, the extent of which depends on the temperature-time combinations, the heating method utilized, and milk pre-treatment conditions [1-3].

Interplay between Residual Protease Activity in Commercial Lactases and the Subsequent Digestibility of β-Casein in a Model System.

One of the conventional ways to produce lactose-hydrolyzed (LH) milk is via the addition of commercial lactases into heat-treated milk in which lactose is hydrolyzed throughout storage. This post-hydrolysis method can induce proteolysis in milk proteins due to protease impurities remaining in commercial lactase preparations. In this work, the interplay between lactose hydrolysis, proteolysis, and glycation was studied in a model system of purified β-casein (β-CN), lactose, and lactases using peptidomic methods. With a lactase presence, the proteolysis of β-CN was found to be increased during storage. The protease side-activities mainly acted on the hydrophobic C-terminus of β-CN at Ala, Pro, Ile, Phe, Leu, Lys, Gln, and Tyr positions, resulting in the formation of peptides, some of which were N-terminal glycated or potentially bitter. The proteolysis in β-CN incubated with a lactase was shown to act as a kind of “pre-digestion”, thus increasing the subsequent in vitro digestibility of β-CN and drastically changing the peptide profiles of the in vitro digests. This model study provides a better understanding of how the residual proteases in commercial lactase preparations affect the quality and nutritional aspects of β-CN itself and could be related to its behavior in LH milk.

Short communication: Volatiles in microfluidized raw and heat-treated milk

As innovative processing equipment is introduced to milk processing, it is essential to determine its effect on milk aroma, a critical factor in consumer acceptance of the final dairy product. Microfluidization is known to cause severe high-pressure homogenization of milk fat and, although severe processing is known to release undesired aromas, no information is available on the levels of the volatile compounds in milk immediately after microfluidization. We hypothesized that microfluidization would alter levels of volatile compounds in milk that may affect aroma. The concentration of 11 selected volatile compounds in raw, thermized, pasteurized, and UHT 3.0% fat milk samples were compared before and after microfluidization at 170 MPa and common 2-stage homogenization at 15 MPa. Overall, the different milk samples had similar trends in response to homogenization, although UHT milk started with lower values of nonanoic acid, and acetone and higher levels of hexanal and heptanol. In many cases, microfluidization did not significantly alter volatile levels compared with the starting milk. Heptanal was the only compound observed to increase in thermized and UHT milk, whereas nonanoic acid and acetone decreased in raw, thermized, and pasteurized milks and octanoic acid decreased in thermized and UHT milks. The highest levels of almost all of the volatiles were found in the 2-stage homogenized milk. Overall, microfluidization had minimal effect on the volatile compound profiles of milk, although sensory evaluation is needed to confirm effects on aroma and flavor.

Concerns and solutions for raw milk from vending machines

The sale of raw milk from vending machines is allowed in several European Countries. Since unpasteurized milk could harbor foodborne pathogens, the boiling treatment is highly recommended before consumption. In this study, the effect of storage temperatures, generally recorded in domestic refrigerators, as well as the effect of domestic boiling and industrial microwaving on the microbiological, and nutritional quality of raw bovine milk from vending machines was evaluated. Results highlighted that some microbial groups increased during the storage at 8°C. Noticeable, Listeria spp., even if initially present in low amounts, reached levels that would be a cause of concerns. Based on these results, the effects of domestic boiling and microwaving on the survival of L. innocua intentionally added was evaluated, as well as the nutritional features of treated milk. Both treatments were able to eliminate L. innocua, but only microwaving preserved the nutritional quality of milk. Practical applications This study presents the application of microwaving as an alternative treatment to enhance the quality of raw bovine milk. Domestic storage conditions (especially refrigeration temperatures and time) produce a strong decay in the microbiological quality of the product and Listeria levels might become a real concern. In addition, boiling treatment, imposed by law prior to milk consumption, produces a further depletion of the nutritional quality, producing a strong decay in thermolabile compounds. A suitable solution for heat treatment of raw milk from vending machines could be represented by microwaving at 780 W for 1.35 min. This datum could serve for setting a specific program in domestic microwave ovens for sanitization of raw milk in home environments.

Effects of feed iodine concentrations and milk processing on iodine concentrations of cows' milk and dairy products, and potential impact on iodine intake in Swiss adults.

The contribution of milk and dairy products to daily iodine intake is high but variable in many industrialised countries. Factors that affect iodine concentrations in milk and dairy products are only poorly understood. Our aim was to: (1) assess the effect of feed iodine concentration on milk iodine by supplementing five groups of five cows each with one of five dosages from 0-2 mg iodine/kg DM; (2) quantify iodine losses during manufacturing of cheese and yogurt from milk with varying iodine concentrations and assess the effect of cellar-ripening; and (3) systematically measure iodine partitioning during heat treatment and skimming of milk. Milk iodine reached a near-steady state after 3 weeks of feeding. Median milk iodine (17-302 μg/l for 0-2 mg iodine/kg DM) increased linearly with feed iodine (R2 0·96; P < 0·001). At curd separation, 75-84 % of iodine was lost in whey. Dairy iodine increased linearly with milk iodine (semi-hard cheese: R2 0·95; P < 0·001; fresh cheese and yogurt: R2 1·00; P < 0·001), and cellar-ripening had no effect. Heat treatment had no significant effect, whereas skimming increased (P < 0·001) milk iodine concentration by only 1-2 μg/l. Mean daily intake of dairy products by Swiss adults is estimated at 213 g, which would contribute 13-52 % of the adults' RDA for iodine if cow feed is supplemented with 0·5-2 mg iodine/kg DM. Thus, modulation of feed iodine levels can help achieve desirable iodine concentrations in milk and dairy products, and thereby optimise their contribution to human iodine nutrition to avoid both deficiency and excess.

Effects of thermized donkey milk with lysozyme activity on altered gut barrier in mice exposed to water-avoidance stress

Nutrition plays a crucial role in human gut health through the improvement of gut barrier functionality. Donkey milk represents an interesting source of natural antimicrobial factors such as lysozyme. Recently, anti-inflammatory properties of donkey milk lysozyme activity were described in a mouse model of ileitis. The current increase of donkey milk consumption highlights the necessity to propose a healthy milk compliant with microbiological standards. This study aims to define a heat treatment of donkey milk, retaining its high lysozyme activity, and to evaluate its beneficial effects on a gut barrier impairment model due to chronic stress in mice. To perform this experiment, samples of raw donkey milk were collected in 15 distinct French farms. Microbiological analysis and lysozyme content and activity were evaluated for each sample. Then, several heat treatments were carried out to define a time and temperature combination that allowed for both a reduction in the number of total micro-organisms, increasing the shelf-life of the product, and preservation of lysozyme activity. The beneficial effect of heated donkey milk on the gut barrier of mice was evaluated and compared with raw donkey milk. We found that samples of raw donkey milk showed low total mesophilic microbial counts, and no pathogens were detected. Among the different heat-treatment procedures tested, a 2-min, 72°C combination was determined to be the most optimal time and temperature combination to preserve lysozyme activity and increase the shelf-life of donkey milk. Oral administration of this heat-treated donkey milk in mice counteracted chronic stress-induced intestinal damage, illustrated by gut hyper-permeability and low-grade inflammation, similar to raw donkey milk. We have demonstrated for the first time that oral intervention with donkey milk, optimally heat-treated to retain enzymatic lysozyme activity, improves intestinal barrier damage linked to psychological stress in mice.

Prospects of HSP70 as a genetic marker for thermo-tolerance and immuno-modulation in animals under climate change scenario.

Heat stress induced by long periods of high ambient temperature decreases animal productivity, leading to heavy economic losses. This devastating situation for livestock production is even becoming worse under the present climate change scenario. Strategies focused to breed animals with better thermo-tolerance and climatic resilience are keenly sought these days to mitigate impacts of heat stress especially in high input livestock production systems. The 70-kDa heat shock proteins (HSP70) are a protein family known for its potential role in thermo-tolerance and widely considered as cellular thermometers. HSP70 function as molecular chaperons and have major roles in cellular thermotolerance, apoptosis, immune-modulation and heat stress. Expression of HSP70 is controlled by various factors such as, intracellular pH, cyclic adenosine monophosphate (cyclic AMP), protein kinase C and intracellular free calcium, etc. Over expression of HSP70 has been observed under oxidative stress leading to scavenging of mitochondrial reactive oxygen species and protection of pulmonary endothelial barrier against bacterial toxins. Polymorphisms in flanking and promoter regions in HSP70 gene have shown association with heat tolerance, weaning weight, milk production, fertility and disease susceptibility in livestock. This review provides insight into pivotal roles of HSP70 which make it an ideal candidate genetic marker for selection of animals with better climate resilience, immune response and superior performance.

The relationship between the number of consecutive days with heat stress and milk production of Holstein dairy cows raised in a humid continental climate

Heat stress is known to affect performance of dairy cows experiencing prolonged periods of high temperature and relative humidity. Less is known about its effects in cooler climates. The goals of the present study were to determine the prevalence of days susceptible to cause mild heat stress in dairy cows living in a humid continental climate and to investigate the relationship between the number of consecutive days of mild heat stress and milk, fat, protein, and lactose production. A 6-yr data set (2010-2015) containing 606,031 milk analysis records for 34,360 Holstein dairy cows at different parities was matched with the corresponding daily maximum temperature-humidity index. Exposure to heat stress conditions was divided into 5 categories corresponding to 0, 1 to 2, 3 to 4, 5 to 6, and 7 to 8 consecutive days before milk test date. On average, cows were exposed to heat stress conditions for 135.8 ± 5.9 d/yr in Southwest Quebec and 95.3 ± 10.2 d/yr in Eastern Quebec. Cows experiencing heat stress conditions produced on average less fat, protein, and energy-corrected milk and lower fat and protein concentrations. The decrease in milk fat reached 6% for category 7 to 8 exposure of cows in parity 3 or more. The association between exposure category and milk yield and lactose yield and concentration was weak. Heat stress lowered milk fat and protein production but had little effect on milk volume output. Further research is necessary to better understand the mechanism underlying the effects of sporadic low- to medium-intensity heat stress on dairy productivity.

Application of qualitative tests for detection of adulterants in pasteurized milk and during its subsequent storage

Effect of widely used heat treatments of milk on performance of selected qualitative tests for detection of common adulterants in the milk was carried out. Genuine and adulterated samples of milk were heated to 72°C for 16 sec for pasteurization. The samples of pasteurized milk were stored at temperature of 5±1ºC. The qualitative tests were performed for detection of adulterants at an interval of 24 hours. The performance of the qualitative tests varied depending on type of heat treatment employed in processing of milk, length of storage period for which samples were stored and chemical nature of the target adulterant spiked in the milk.

The Effect of Eight Thermal Protectants on the Survival Rate and the Viable Counts of Lactobacillus casei After Heat Treatment in Fermented Goat Milk

Abstract In order to improve the survival rate of probiotics and produce probiotic goat milk from fermented goat milk of Lactobacillus casei L61 by spray drying. Spray drying has been applied to large-scale industrial production of milk powder due to its high efficiency and low cost. However, high temperatures in spray drying can result in the loss of large numbers of probiotic.The purpose of this paper is to study the effects of eight thermal protectants including skim milk, sucrose, glucose, β-cyclodextrin, gelatin, maltodextrin, glycerol, trehalose on the survival rate and viable counts of L.casei L61 after heat treatment by the single factor experiment. All protective agents have a positive effect on increasing the survival rate of L.casei L61 (p&lt;0.05). The results indicated that the survival rates of L.casei L61 were up to the maximum of 10.94%, 1.13%, 3.04%, 0.21%, 6.97%, 0.075, 4.71% and 0.29%, while the additions of skim milk, sucrose, glucose, β-cyclodextrin, gelatin, maltodextrin, glycerol, trehalose were 20mg/L, 10%, 7%, 15%, 1.5%, 3%, 8mL/L, 10%, respectively; the viable counts after heat treatment are 19.69, 0.81, 1.78, 0.455, 12.2, 0.12, 2.75, 0.435(×106CFU/mL), respectively. This paper provides technical a reference for the development of probiotic goat milk powder.

Evaluate the Chemical and Microbiological Quality of Laban Rayeb Manufactured

Laban rayeb manufactured under a good sanitation and hygiene conditions from lactic acid bacteria isolated, from Laban Rayeb Produced by small dairy plant in Assuit city, Cow’s milk heat treated at 73 ° C and cooled to 37 ° C were inoculated by either isolated Lactobacillus sp or Streptococci sp culture or mixture of them at 1: 1 by weight, to produce a Laban Rayeb in sterile laboratory conditions. The produced Laban Rayeb analyzed as fresh and during period stored for 15 days at 5 ± 2 ° C. The mean acidity, total solids, total nitrogen and soluble nitrogen content ​​in control Laban Rayeb were of 0.7, 11.36 ,0.44, and 0.112 % on the first day of storage which increased to 0.76, 11.52 ,0.49 and 0.169 % after 15 days of storage respectively .While the mean acidity, total solids, total nitrogen, and soluble nitrogen in the samples of Laban Rayeb made by Streptococci sp were of 0.74, 11.33, 0.44 and 0.114 % on the first day of storage which increased with storage to 0.95, 12.22, 0.61 and 0.160 % after 15 days. While these Acidity, Total solid, total nitrogen and soluble nitrogen values of Laban Rayeb inoculated by Lactobacillus sp were 0.76, 11.16, 0.45 and 0.103 %, at first day of storage, which increased to 0.96, 11.75, 0.59, and 146% after 15 days of storage respectively. The Laban Rayeb produced using Lactobacillus sp and Streptococci sp gave the following values 0.84, 11.36, 0.42 and 0.123% ​​ respectively and by increasing the storage period these values acidity, total solids, total nitrogen and soluble nitrogen values were increased to reach 1.2, 11.9, 0.55 and 0.192% after 15 days of storage respectively. The total bacterial count values ​​in control Laban Rayeb, Laban Rayeb made by single Streptococci sp, by single Lactobacilli sp and by mixed Lactobacillus sp and Streptococci sp respectively were of 5.12, 6.21, 6.27, 6.29 log (cfu/ml) on the first day of storage and increased to 8.87, 9.13, 9.20 , 8.64 log (cfu/ml) after 15 days of storage. While The mean Logarithm of lactic acid bacteria of Lactobacilli sp. count values ​​in control Laban Rayeb, Laban Rayeb produced by Streptococci sp, Lactobacilli sp and Lactobacillus sp and Streptococci sp were of 5.22, 5.46, 7.14, 7.15 log (cfu/ml) on the first day of storage and increased to 7.73, 8.13, 9.22, 9.46 log (cfu/ml) after 15 days of storage , The mean Logarithm of Streptococci sp. values ​​in control Laban Rayeb, Laban Rayeb produced by Streptococci sp, Lactobacilli sp and Lactobacillus sp mixed with Streptococci sp were of 4.86, 6.93, 4.12, 7.15 log (cfu/ml) on the first day of storage and increased to 7.42, 9.98, 8.17, 8.76 log (cfu/ml) after 15 days of storage ,The mean Logarithm count of lactic acid bacteria of proteolytic bacteria values ​​in control Laban Rayeb, Laban Rayeb made by Streptococci sp, Lactobacilli sp and mixed of Lactobacillus sp and Streptococci sp were 1.61, 3.54, 3.18, 3.32 log (cfu/ml) on the first day of storage which increased to 5.34, 6.45, 6.56, 6.75 log (cfu/ml) after 15 days of storage . Molds and yeasts and coliform bacteria were not detected.

Peptide profile of Camembert-type cheese: Effect of heat treatment and adjunct culture Lactobacillus rhamnosus GG.

Several factors might impact the proteolysis during cheese manufacture and ripening and, therefore, the release of bioactive peptides. These factors include the heat treatment of the milk, the type of starter and secondary culture used and the ripening time. Thus, the objective of this study was to evaluate the effect of the milk heat treatment and the use of adjunct culture in the development of the peptide profile of Camembert-type cheese during ripening. The cheeses were made from raw and heat-treated milk, with and without the addition of Lactobacillus rhamnosus GG. The results obtained by mass spectrometry (MALDI ToF/MS) and analyzed by chemometrics (PLS-DA) revealed a complex hydrolysis profile of the caseins with 103 peaks found, of which 70 peptides were identified and 15 presented bioactive potential. The potential bioactive peptides important for the separation of cheeses were all derived from β-casein. The heat treatment of the milk, the addition of the adjunct culture and the ripening time affected the peptide profile of the cheeses. At the beginning of ripening the cheeses presented a very similar peptide profile, which differed over time, and this differentiation is clearer for cheeses obtained from raw milk.

Dielectric properties, effect of geometry, and quality changes of whole, nonfat milk powder and their mixtures associated with radio frequency heating

Radio frequency (RF) heating is a promising pasteurization technique providing a fast and more uniform heat generation throughout a sample. In this paper, the effect of composition, frequency (1–30 MHz) and temperature (20–90 °C) on the dielectric properties of whole, nonfat milk powder and their mixtures were studied to develop an effective RF pasteurization. Moreover, the effect of the shape and dimension of the container on RF heating were evaluated. Milk powders were loaded into rectangular and cylindrical boxes with the same volume and different heights (3, 6 and 9 cm), and heated in a 6 kW, 27.12 MHz pilot scale free-running oscillator RF oven. The heating rate, temperature profile, penetration depth, and electric field strength were determined. The quality of the RF heated milk powders was evaluated by measuring moisture content, water activity, solubility, and color. Overall, heating milk powder in the 6 cm height cylindrical box showed a relatively more uniform temperature distribution than 6 cm height rectangular box, with moderate heating rate as well as improved quality in the finished product with less changes in moisture content, water activity, solubility and color. Electric field strength increased with the increase in the height of the container.

MICROBIOLOGICAL CRITERIA IN THE MANUFACTURE OF PASTEURIZED MILK

The process hygiene criterion is a microbiological criterion that applies to the process offood production and processing and indicates the proper functioning of the production process byrepresenting the value of the contamination above which corrective measures are taken to maintainthe process hygiene. Pasteurized milk is a product obtained by heat treatment of raw milk at atemperature of 63° C for 30 minutes or 72° C for 15 seconds. Pasteurization has two purposes, thefirst one is to elimination of all pathogenic microorganisms, and the second is to reduce the numberof saprophytic microorganisms, which prolongs the shelf life without changing the nutritional andbiological value of the milk.The aim of the study is to examine the safety of pasteurized milk and the conditions of hygiene inthe production process based on the results of the examination of pasteurized milk on the criteria ofhygiene in the production process, as well as to develop a proposal for the recommendedmicroorganisms to be tested in the process of the production of pasteurized milk.Samples of pasteurized milk come from a pasteurizing plant that purchases milk from the territoryof Republika Srpska, and were sampled in the six-month period (January-June), within self-controland official control. For microbiological testing of raw milk, standard BAS ISO methods were used.The results of pasteurized milk testing in relation to the hygiene criteria in the production processare satisfactory in relation to the Rulebook on Microbiological Criteria for Food. The results of selfcontrolon the recommended microbiological criteria in the process of obtaining pasteurized milk,which are given in the Guideline on the Application of Microbiological Criteria for Food, aresatisfactory in relation to the finding of Listeria monocytogenes, Salmonella spp. and coagulasepositive staphylococci, and unsatisfactory for a number of microorganisms.The results of official controls in the production process of pasteurized milk are unsatisfactory dueto the increased number of microorganisms in 12.50% of the samples. 22.20% of pasteurized milksamples had the number of microorganisms larger than 105CFU/ml within self-control and officialcontrols. Examination of pasteurized milk in the self-control of the production process should beperformed on enterobacteria and the total count of microorganisms, and in the interpretation of theresults the recommended limit values from the Guideline on the application of microbiologicalcriteria for food should be used.