The aim of this study was to determine the effects of fatty acids and triglycerides composition on melting behavior of milk fat. The melting profiles, fatty acids composition and triglycerides composition of milk fat from 27 cows fed palm oil, rapeseed oil and a low fat diet were analyzed. Correlations between individual fatty acids and triglycerides, and the melting off-set temperatures of milk fat fractions were obtained using multivariate data analysis. Low fat feeding increased the proportion of short and medium chain fatty acids and decreased the proportion of long chain fatty acids. The opposite effect was observed in milk fat of cows from lipid supplemented diets. Palmitic and myristic acids correlated positively to the melting off-set temperatures of high melting fraction of milk fat while oleic and linoleic acid had strong negative correlations. Furthermore, high molecular weight triglycerides contributed positively to the melting off-set temperatures of high melting fraction of milk fat. This is the first study to demonstrate that the melting off-set temperatures of high melting fraction of milk fat can be affected, to some extent, by dietary manipulations of cows. However, melting off-set temperatures of milk fat were still under physiological temperatures of cows indicating that the biological mechanism secure full milk fluidity under most dietary manipulations. Knowledge from this study could help to characterize melting fractions of milk fat resulting from different feeding regimes. This could aid in milk fat fractionation for use in specialty ingredients or modification of functionality of milk fat (e.g. softness or spreadability) in fat-based products.
Udder quarters suffering from chronic and therapy-resistant infections represent a serious problem for dairy farms. Drying off such udder quarters during lactation would offer an opportunity to remove these single quarters from milk production without losing the whole milk yield of one cow during the current lactation. The use of a casein hydrolysate (CNH), an enzymatic fission product of casein, hence an endogenous substance, showed promising results regarding downregulation of milk secretion in udder quarters of high yielding dairy cattle in previous investigations in Israel. The objective of this study was to prove whether the infusion of CNH into the bovine mammary gland is an appropriate method to downregulate milk secretion in chronically infected udder quarters in high yielding dairy cows in Germany in order to dry off these single quarters without inducing clinical mastitis. Each treated udder quarter received six intracisternal infusions of CNH within 3 treatment days. After the last infusion of CNH on day 3, milking of the affected udder quarter was stopped. In 21 out of 24 (87.5 %) quarters a successful drying off could be achieved and only three quarters showed clinical mastitis. Furthermore, none of the animals showed a defence response or signs of pain during the intracisternal application. An increase in the average somatic cell score (SCS) during the treatment period could be revealed and 11 out of 16 conventionally milked quarters showed a decrease in milk yield. Hence, it could be shown that the infusion of CNH is an effective and gentle method for downregulating milk yield and drying off chronically infected and therapy-resistant single udder quarters during lactation.
Bovine mastitis is commonly treated with antibiotics, which does not always succeed and therefore, sometimes is unnecessary. Bacteriological cure is the goal of antibiotic therapy and depends on the causing microorganism, the applied therapy, and on animal-related factors. Determining the animal-related part of the probability of bacteriological cure before applying antibiotics might help to reduce unnecessary usage. By now, this is only possible by considering individual cow data including animal-related factors such as age, mastitis history and somatic cell count. Former studies revealed that chronic mastitis lowers the probability of cure and leads to specific characteristics found in the differential cell count. The aim of this study was to develop a flow cytometric cell differentiation tool to determine animal-related factors correlating with a score-based probability of bacteriological cure. Therefore, the proportions of different cell types and their vitality in 874 Dairy Herd Improvement milk samples of 239 cows were determined by flow cytometry. The results were tested for a correlation between data of flow cytometry and the calculated animal-related probability of bacteriological cure of each individual cow by binomial logistic regression analysis. A statistically significant association to the calculated and animal-related probability of bacteriological cure could be shown for highly granulated cells, non-vital cells and macrophages. With this model, 84.4 % of all animals could be allocated to their estimated animal-related probability of bacteriological cure correctly. These findings suggest that flow cytometric cell differentiation might become an innovative tool to estimate animal-related prognosis for bacteriological cure.
The compositional and physical parameters of alcohol positive milk (APM) of different buffalo breed were studied and compared with their average of total milk samples for one year. Total 966 milk samples were collected from four buffalo breeds, Murrah, Nili-Ravi, MurrahxChinese local buffalo (Mu-Ch) and MurrahxNili-RavixChinese buffalo (Mu-Ni-Ch) and were analyzed for alcohol stability at 64%, 66%, 68% and 70% (v/v) of alcohol. Results of milk compositional and physical parameters differ significantly (P <0.001) among the breeds. The APM rates of Mu-Ch and Mu-Ni-Ch were higher than Murrah and Nili-Ravi. The APM had higher acidity, milk protein and non-fat solids (NFS) and lower freezing point than average of total milk samples. When comparing different buffalo breeds the APM rates seemed mainly positive related to acidity and no special relationships with other parameters. In conclusion, a fixed alcohol level was not suitable for milk from different buffalo breeds for the alcohol test. Milk with higher acidity, protein, NFS and lower freezing point has higher sensitivity to alcohol in different buffalo breeds, and alcohol stability showed mainly a positive relation to milk acidity.
The aim of this study was to investigate the fuzzy modelling of the effect of the swelling power (SP) of starch and water absorption capacity (WAG) of gum on rheological behaviour of model. Six different starches and six different gums having different SP and WAG were used in model instant hot chocolate formulation for this aim. All of the samples were fitted to herschel bulkley model within the R-2 values that ranged between 0.996-0.999. The consistency index (K), flow behaviour index (n) and yield stress values (sigma(0)) of the samples varied between 2.30-118.20 mPa s(n), 0.587-1.095 and 33-186.8 mPa, respectively. In addition, an adaptive neuro-fuzzy interference system was used to model and identify the sigma(0), K and n based on SP of starch and WAG of gum. Fuzzy modelling technique yielded a very satisfactory prediction accuracy of 99% for each parameter.
Milk remains one of the most elaborately studied human food, and its proteins are known to be source of a range of bioactive peptides. Angiotensin converting enzyme (ACE) inhibitory peptides are one of the bioactive peptides, produced mostly from milk casein by trypsin digestion. In the present study, isoelectric casein from buffalo (Bubalus bubalis) milk was isolated and fractionated to alpha, beta and kappa-casein. These casein fractions were separately hydrolysed with trypsin (EC 3.4.21.4) and angiotensin converting enzyme inhibitory (ACEI) activity was measured. Molecular size of casein and its hydrolysates were determined by Tricine-SDS polyacrylamide gel electrophoresis. Further, number of peptides generated by hydrolysis and its relative hydrophobicity was seen in Reverse Phase-High Performance Liquid Chromatography (RP-HPLC). The individual fractions from alpha, beta and kappa-caseins were found to be 12.1 +/- 2.1, 10.6 +/- 1.8 and 4.2 +/- 1.4 g/L in buffalo milk having molecular weight of in the range of 19 to 25 kDa. Molecular weight of casein hydrolysates were <= 3 kDa. Among all casein fraction hydrolysates, beta-casein shows maximum ACE inhibition activity. This study clearly depicted the presence of ACE inhibitory peptides in buffalo milk.
This investigation was carried out to evaluate the extent of bioactive peptides that can be obtained from proteolytic enzymes, including alcalase, flavorzyme, neutrase, and protamax. For this purpose, whey protein concentrate (WPC) was hydrolyzed, spray-dried, and subjected to mass spectrometric analysis. In addition, offline-electrospray-ionization-mass spectrometry (ESI/MS) measurements and offline-matrix-assisted laser desorption/ionization mass spectrometry (MALDI/MS) measurements were compared to determine analytical adequacy. Samples treated with alcalase for 3 hours produced various bioactive peptides, suggesting the possible application of this method to functional food preparations. Comparison of both ionization methods indicated ESI/MS as suitable for the identification of peptides from whey protein hydrolysates.
This study examines the effect of pressurisation on the composition of milk fat triacylglycerols, which determines its crystallization properties and, consequently, the rheological properties of dairy products. The raw material used in this study was anhydrous milk fat from the stall feeding period, obtained from "extra" type butter, purchased from one of the production plants in north-eastern Poland. Treatment pressure (100, 200, 300 and 400 MPa) and a range of process temperatures (10 and 40 degrees C) were the differentiating parameters. The process of pressurisation was conducted in a U 4000/40 type device manufactured by the Unipress Equipment Division. The results showed that parameters of milk fat pressurisation applied in the experiment did not affect the composition of analysed groups of triacylglycerols in the TAG C26 to TAG C54 range. A two-factor analysis of variance revealed stability of the composition of triacylglycerols in milk fat subjected to pressurisation, regardless of the pressure conditions applied: 100, 200, 300 or 400 MPa, and irrespective of the temperature of the process, 10 or 40 degrees C.
The characteristics of heat-induced acid whey protein concentrate (AWPC) gels with added caseinomacropeptide (CMP) were studied in a model system prepared from freshly prepared AWPC and purified CMP derived from raw milk. The resulting AWPC was compared to commercial WPC and found to be quite similar based on its overall chemical composition. As CMP was added to the AWPC, the strength of the heat-induced gels decreased significantly as did the measured degree of intermolecular disulfide bond formation. Scanning electron microscopy indicated that the gels with higher CMP developed a coarser structure with larger pores and a looser structural network when compared to purely AWPC gels. CMP was also capable of forming weak gels that were structurally very different from AWPC gels, being more of an aggregate than a three-dimensional network. Differential scanning calorimetry (DSC) demonstrated substantive changes in the denaturation behavior of samples containing increasing levels of CMP. Based on the results obtained as well as literature data, CMP has a strong negative impact on the gel strength of WPC gels, indicating that the evaluation of the CMP content in commercial formulations be considered if gelation is an important functional requirement.
A total of 34 presumptive Bacillus cereus cultures were isolated from dried milk products and confirmed on a selective chromogenic BACARA medium as B. cereus. Fatty acids from the colony's material were extracted using n-hexane and methylated with a KOH methanol solution yielding methyl esters. Fatty acids were separated using a gas chromatograph equipped with flame ionization using a 120 m BPX-70 column. A "Supelco 37 Component FAME Mix" reagent kit was used for the identification of fatty acids. Fatty acids produced by more than 50% of all investigated B. cereus were assumed as typical for these isolates. A total of 23 typical fatty acids were identified in B. cereus. There were significant differences in the amounts of fatty acids produced between B. cereus isolates. All B. cereus isolates produced butyric, palmitoleic, oleic and docosahexaenoic fatty acids in the largest amounts of the total fatty acid content. Ten of typical fatty acids in individual B. cereus isolates appeared as minor components and their amounts were less than 2% of the total fatty acid content. Cluster analysis closely related all the isolates. The main difference between the isolates clustered into two groups was the absence of capric and undecanoic fatty acids in group 2.
The viscosity of highly concentrated skim milk stored at low temperature for several days increased markedly and crystallization of lactose took place. The viscosity and the degree of lactose crystallization increased as the total solids content increased. The effect of lactose crystallization on the change in the viscosity of concentrated skim milk at low temperature was examined by controlling the crystallinity of lactose, showing that lactose crystallization promoted the increase in its viscosity. Because the composition changes indicated the significant decrease in soluble lactose as crystallization proceeded, we examined the role of soluble lactose in concentrated skim milk by using sucrose instead of lactose in this experiment. The results showed that the addition of sucrose efficiently decreased the viscosity, suggesting the possibility of a stabilizing effect of soluble lactose in concentrated skim milk. The size distribution of casein micelles suggested that interactions between casein micelles in concentrated skim milk after the significant increase in the viscosity were weak and reversible.
Lactic acid bacteria (LAB), citrates fermenting LAB, vancomycin tolerant LAB, vancomycin tolerant citrate fermenting LAB, Lactobacillus spp. and yeasts of 30 Polish ripened cheeses of Dutch, Dutch-Swiss and Swiss types were studied. Non-starter lactic acid bacteria (NSLAB) and yeasts were the predominant microflora in the cheeses. The populations of vancomycin tolerant LAB, lactobacilli and yeasts were in the ranges of 6.7-6.9, 5.6-6.3 and 5.4-5.9 log(10) cfu/g, respectively. The highest microbial variability was found for vancomycin tolerant citrate fermenting LAB. Their numbers varied from non-detectable levels in 22 cheeses to a bacterial population greater than 8 log cfu/g. No quantitative interdependence between yeasts and NSLAB populations was found in the cheeses. The results showed that different sources of yeasts and NSLAB may have caused contamination of cheeses in the dairy plants. Although, NSLAB and yeast counts varied between plants producing the same types of cheese, many factors such as production equipment and advanced automation systems could have influenced the microbial profile. The microflora of NSLAB could vary significantly depending on the type of cheese, yet it is influenced more by the environment of the manufacturing plant.
This study was undertaken to determine the effect of microbiological transglutaminase (mTG) on the physicochemical properties of stirred kefir. The monitoring of pH demonstrated that changes caused by the catalytic activity of mTG had no effect on the dynamics of the acidification process. The evaluation of stirred kefir produced under laboratory and industrial conditions demonstrated that values of viscosity and texture parameters of the samples with mTG were significantly higher as compared to the products without the enzyme. Changes proceeding during cold storage were observed to increase values of firmness, thickness, cohesiveness, and viscosity index of curd of the kefir samples with mTG. Organoleptic traits of the mTG-containing samples were scored higher than these of the samples without the enzyme, most of all owing to full flavour as well as smooth and creamy texture. The application of transglutaminase in the production of kefir extends the possibilities of modeling the rheological and organoleptic properties of these products.
Listeria monocytogenes is a foodborne pathogen commonly found in food and environment. Raw and market milk samples (n= 767) were collected at different levels of collection and processing for isolation of Listeria species. The samples taken included cow milk collected at udder level, from the milk cans, milk receiving centres, processing unit and market. Samples were enriched in Listeria enrichment broth followed by plating on PALCAM agar. Overall, 10.56% of the samples (81 of 767) were positive for Listeria species. Out of these 37 (4.82%) were confirmed as L. monocytogenes. Other Listeria species isolated were L. innocua (5.47%), L. ivanovii (0.13%) and L. grayi (0.13%). Maximum isolates were recovered from samples collected at market followed by samples at milk processing unit. L. monocytogenes isolates were serotyped using multiplex PCR method. A larger proportion of isolates (26) belonged to the group corresponding to serovars 1/2a, 1/2c, 3a, and 3c. Serogroup corresponding to serovars 4b, 4d and 4e was detected in two strains, while serogroup 1/2b, 3b, 4b, 4d, and 4e was detected in nine strains. This study demonstrates the prevalence of L. monocytogenes in raw and market milk and the need for good hygienic practices to prevent its entry into the food chain.
Application of kefir as a delivery vehicle of Bifidobacterium (Bif.) lactis HN019 (TM), Lactobacillus (Lb.) acidophilus NCFM (R) and Lb. rhamnosus HN001 (TM) for human consumption was studied. Growth and viability of probiotics strains as well as kefir microflora development during manufacturing and 4-week cool storage of kefir were evaluated. Additionally, probiotics impact on fermentation time and sensory properties of kefir were determined. Cell count of HN019 and NCFM did not increase in kefir manufacturing conditions, while the population of Lb. rhamnosus HN001 increased by 2.5 times. Probiotics at studied inoculation rate of milk 10(6) - 10(7) cfu/ml did not show adversely impact on the kefir microflora balance as well as essential fermentation time. Viability of the probiotic strains was satisfactory for the entire shelf life of the kefir with excellent stability up to 3 weeks. Sensory properties of kefirs with probiotics did not differ from the controls except for HN019 with small difference at 10(7) cfu/ml inoculation rate. The results indicated kefir potential as a probiotic delivery vehicle. Additionally probiotics can enhance kefir health image and increase its attractiveness for consumers.
The objective of this study was to measure the survival and growth of yogurt culture (Y1 885) in MRS broth in the presence of rodenticides and to determine whether yogurt culture could eventually be used as a biomarker to detect rodenticides in milk. Serially diluted rodenticides were added to tubes containing MRS broth. Commercial yogurt culture was then inoculated in MRS broth sample and incubated at 42 degrees C for 6 hours. The Optical Density (OD 610 nm) and pH of the broth were recorded at 2, 4, and 6 hour intervals. The bacterial counts, alpha-galactosidase and beta-galactosidase activity were also measured at the end of incubation. The yogurt cultures showed detectable sensitivity (significant change (p<0.05) in OD in the medium) to diphacinone at 0.005mg/ml, to brodifacoum at 0.02 mg/ml, and to bromadiolone at 0.06 mg/ml. There were significant differences (p<.05) in the bacterial count, pH, alpha-galactosidase and beta-galactosidase activity in the presence of toxins in the medium. The results indicate that yogurt culture could be used as a biomarker for the early detection of rodenticides in milk. With some adjustments, this process could be utilized as a fast and accurate test for the presence of pesticides in dairy food products.
The aim of the study was to evaluate and compare selected physical properties of instant puddings for differences determined by the manufacturer. In studies the selected physical and mechanical parameters including variation of the material in terms of the raw materials used in the production process and (although largely unknown) the technological operations were characterized. The studies included determination of granulometric composition, bulk density loose and tapped, the angle of repose of various surfaces, piling angle, wettability, water content and sorption properties (GAB model) in the specific surface sorption, the total volume of capillaries and the most probable radius of the capillaries. The study results demonstrated that the technology (determined by the raw materials and technology operations) significantly affects the properties of food powders as perceived by the consumer.
The object of this study were to determine the effect of apple and lemon fibers on the physical, chemical, microbiological and sensory properties of low fat kefir and to investigate whether or not the probiotic properties of the samples were maintained throughout storage period of 20 days at 4 degrees C. Low fat UHT cow's milk was mixed with apple fiber (1-2 %) and lemon fiber (1-2 %). Control sample wasn't mixed with any fiber. Milks were inoculated with 4-percent kefir culture and fermented up to pH 4.7 at 25 degrees C. Differences were obtained in the levels of dry matter, fat, lactose, ash, pH, SH and tyrosine of kefir samples supplemented with or without apple or lemon fibers at different concentrations (P > 0.05). While the addition of apple and lemon fiber at lower concentrations increased the viscosity in kefir, viscosity was decreased at higher levels (P < 0.05). Supplementation of kefir with fibers did not adversely affect the counts of Lactobacillus spp. and Lactococcus spp. (P < 0.05). More research is needed to improve the organoleptic properties of the kefir samples supplemented with apple and lemon fibers.
