Milk Coagulation Time Research Articles

Comparison of milk-clotting activity measurement using the Berridge's operator-based approach and a proposed digital method

The milk clotting activity (MCA) analysis of coagulants used in the production of cheese is an important parameter used in the modern dairy industry. The MCA is calculated using the estimated milk-clotting time (MCT). The standard method used for estimation of MCT is presented in the ISO 23058/IDF 199 Standard using the Berridge's operator-based approach. In this paper a new method is presented to estimate the MCT using digital image acquisition and signal processing. The estimate is obtained by processing a sequence of images of the wall of a round bottom flask containing milk and the coagulant. Digital signal processing and filter techniques were used to remove interferences and artifacts and improve the clotting time estimation. A set of 28 samples of milk plus coagulant were processed. The method's accuracy is about 1/30 s and the average relative error, when compared to an experienced human operator, was με = 2.82%, according to the experimental results, with an associated standard deviation of σε = 3.07% and a median of mε = 1.92%. The method may be used to replace the human operator during the MCT estimation procedure.

Влияние пробиотиков на молочную продуктивность и технологические свойства молока коз зааненской породы

The article presents the results of experimental studies to study the effect of feeding probiotic feed additives Kluver Pro and BeneFIT Basic on milk productivity, composition and technological properties of milk from Saanen goats. It has been established that feeding probiotics Kluver Pro and BeneFIT Basic as part of the diets of lactating goats of the Saanen breed helps to increase milk yield by 9,5‑4,4% (p≤0,001), the mass fraction of fat in milk - by 0,73% (p≤0,05) and 0,11%, mass fraction of protein in milk - by 0,25% (p≤0,05) and 0,19%, as well as milk clotting time - by 7,3% and 5,4% (p≤0,001) and the formation of a denser rennet curd, which is a desirable property in the production of fermented milk products and cheese making

Factors affecting acid protease production by Mucor circinelloides MG603064.1 through SmF process: characterization and fromage frais making.

The exploitation of food industry wastes and their conversion into value-added products present a promising and continuously growing field, given the diversity of elaborated wastes. The current work aimed to utilize sweet cheese whey as a growth medium for acid protease production by a local fungus strain. The biochemical and physicochemical properties of the cheese whey, such as pH, conductivity, chemical oxygen demand, biological oxygen demand (BOD5), total nitrogen and protein contents, and mineral salts, were assessed using various analytical methods. The effect of certain parameters on acid protease production by Mucor circinelloides MG603064.1 through the SmF process was investigated using the conventional design method "One factor at a time". Subsequent to characterization, the crude extract was used in a trial to create fromage frais, compared to the commercial rennin CHY-MAX® Powder Extra. Cheese whey characterization revealed its richness in total nitrogen (1.044 ± 0.044 g/l), protein content (6.52 ± 0.04 g/l), and principal mineral salts: calcium (1.637 ± 0.037 g/l), phosphorus (1.173 ± 0.023 g/l), and chloride (1.66 ± 0.09 g/l). The optimal values of the SmF process for acid protease production, such as the inoculum size, beef extract, and KH2PO4 supplements, the initial pH of cheese whey, and incubation temperature were, respectively, 11% (v/v), 0.4% (w/v), 0.5% (w/v), 5.5, and 30°C. Under these conditions, the lowest milk-clotting time of 290 s was achieved, representing an 18.41-fold increase compared to the initial step using the unoptimized medium. The enzyme showed maximum milk-clotting activity at pH 5, a temperature of 60°C, and in the presence of 0.025 M of CaCl2. The enzyme activity also significantly improved with sonication (35 kHz) for 10 min. The crude extract of M. circinelloides ensured the production of fresh cheese samples with characteristics roughly similar to those obtained by the control (CHY-MAX® rennin). The acid protease of M. circinelloides could successfully substitute the conventional rennin in the manufacture of fresh cheese.

Effect of coagulating enzymes and types of milk on the physico-chemical, proximate composition and sensory attributes of iron fortified Mozzarella cheese

Mozzarella cheese is an extremely versatile product that has been widely used by the food sector as an essential ingredient in pizza, cheeseburger, cheese-based salads, etc. The main aim of the present investigation is to study the effect of coagulating enzymes and types of milk on the physico-chemical, proximate composition and sensory attributes of iron fortified mozzarella cheese. Iron-fortified mozzarella cheese was prepared using chymosin (control group) and kiwifruit crude extract (treatment group) from three different types of milk (cow milk 100%, goat milk 100%, and cow: goat milk 50:50 ratio). SDS-PAGE of kiwifruit crude extract exhibited protein bands at 24.5 kDa, 20.3 kDa, and 18.8 kDa. The milk clotting time of kiwifruit crude extract exhibited a shorter coagulation time in the presence of CaCl2. Highly significant (p<0.01) difference between enzymes, types of milk, and the interaction effect between enzymes and types of milk were noted for pH. Similarly, a highly significant difference (p<0.01) was observed between types of milk and interaction effect between enzymes and types of milk while a significant difference (p<0.05) was observed between enzymes for titratable acidity. The highest moisture and fat content were noted in the control group for goat and mixed milk cheese while fat, ash, and TS were comparably higher in the treatment group in mixed and goat milk cheese samples. The sensory score of mixed milk cheese enjoyed the maximum ratings by the taste panel members. Based on the findings, the present study suggests that mixed milk iron fortified mozzarella cheese (treatment group) was adjudged the best product compared to cow milk or goat milk mozzarella cheese

Fruit Extract Derived from a Mixture of Noni, Pineapple and Mango Capable of Coagulating Milk and Producing Curd with Antidiabetic Activities.

Morinda citrifolia L. (noni), Ananas comosus L. cv. Sarawak (pineapple) and Mangifera indica L. cv. Apple (mango) represent fruits capable of coagulating milk and forming a curd. Plant-derived milk coagulants have antidiabetic phytochemicals that enrich the curd. Hence this work evaluates the dual benefits of the fruits in coagulating milk and the antidiabetic activities found in the obtained curd. The three fruits were mixed to form a supercoagulant (a milk coagulant mixture of the extracts at a ratio of 1:1:1), and the milk coagulation time was measured. The milk was coagulated by the supercoagulant, and thus fortified curd was tested for its ability to inhibit α-glucosidase and α-amylase activities. Then, the fortified curd was fed daily to streptozotocin-induced diabetic rats and their biochemical markers such as blood glucose level, aspartate aminotransferase, alanine transaminase, etc. as well as histopathology of their liver and kidney tissues were compared with the untreated diabetic rats and normal rats. The supercoagulant had a milk coagulation time of (28±3) s at a 50 mg/mL concentration. Its fortified curd inhibited α-glucosidase and α-amylase activities, with IC50 values of (4.04±0.03) and (3.42±0.02) mg/mL, respectively. The average mass of the streptozotocin-induced diabetic rats fed daily with curd formed by the supercoagulant was (201±10) g on day 20 compared to diabetic control rats with (149±16) g. The blood glucose concentration for rats treated with the supercoagulant after fasting was (15±1) mmol/L compared to the diabetic control rats ((26±2) mmol/L). Blood tests on the treated rats showed aspartate aminotransferase, alanine transaminase, γ-glutamyl transferase and alkaline phosphatase (liver function tests) amounts of (214±78), (91±13), 3 and (510±138) U/L, respectively, while the total protein and renal function tests showed the concentrations of albumin, globulin, urea and creatinine of (37±2) g/L, (30±2) g/L, (11±1) mmol/L and (42±3) µmol/L, respectively. These concentrations were found to be similar to those of the normal rats on day 20. Furthermore, a histopathological study performed on the liver and kidney of the rats found no apparent damage. This supercoagulant derived from a mixture of fruits is able to coagulate milk rapidly, and its curd is fortified with safe antidiabetic agents. The supercoagulant is potentially useful in producing functional dairy food to prevent diabetes or as a supplement for diabetics to control their blood sugar. Such products are capable of replacing dairy products derived from animal enzymes and provide consumers with additional functional dairy products.

Effect of Lactoperoxidase Enzyme System in Improving Shelflife of Raw Milk from Dairy Farms in Khartoum State, Sudan

Lactoperoxidase enzyme (LP) is a natural component in milk with broad spectrum of antimicrobial activity applications in in vivo and in vitro. LP system (LPS) was developed to eliminate the growth of bacterial pathogens and augment the shelf life of raw milk. The aim of this study was to evaluate the effect of activation of LPS on the growth and survival of bacterial pathogens and preserving raw milk quality. A checklist was developed and filled in ten farms at the time of milking to detect the hygienic measures in these farms. Two liters of milk were collected in sterile containers and warmed to 37°C/15min. LPS was activated by dissolving 40mg and 30mg of sodium thiocyanate and sodium percarbonate, respectively, in one liter of milk and followed by thorough mixing. 50ml from this liter of milk was added to two new containers and designated as group B and C. Moreover, group C was supplied with E. coli (106-107 cfu/ml). While milk in group D, LPS was not activated, instead milk was only supplied with E. coli (106-107 cfu/ml). Group A was considered as the control group (neither activated nor supplied with Escherichia coli). Tenfold serial dilution was performed to determine the bacterial total viable count (TVC) and milk clotting time (per seconds) in each group for 2, 4, 6, 8 and 10 hrs. The TVC and the milk clotting time in each group were statistically expressed as pairs between the groups (A versus B; C versus D) with significance probability of P≤0.05. The checklist analysis reflected the bad hygiene measures in the dairy farms. For TVC, in 2hrs incubation; no significant difference was observed between group A versus group B. While group C versus group D showed high significant difference. After 4hrs incubation, TVC showed prominent significance difference between the control compared to group B. While group C versus group D showed no statistical significance differences. At 6hrs time period, a significant difference was observed between the compared groups. However, no significance differences were observed between the groups after 8hrs and 10hrs of incubation. For clotting time, in 2hrs incubation, a significant difference between the compared groups was observed. After 4hrs incubation, a significant difference between the control compared to group B was prominent, while group C versus group D showed no statistical differences in clotting time. However, no significant differences were observed between the groups after 6, 8 and 10hrs of incubation in the clotting times. Taken together these results indicated that the LPS system was efficient until 6hrs and could prolong milk shelf life and prevent milk clotting.

Effects of full-time v. part-time grazing on seasonal changes in milk coagulation properties and fatty acid composition

For this research communication our objective was to investigate to what extent milk coagulation properties and milk fatty acid (FA) composition were affected by different feeding systems, season and their interaction. Eighteen cows in total were subjected to one of three different feeding system treatments: full-time grazing or part-time grazing combined with indoor feeding of fresh grass with low or high concentrate supplementation. Milk was sampled in spring, summer and autumn. Milk coagulation time was 15.0, 19.0 and 17.7 min, coagulation dynamics 1.67, 3.41 and 1.79 min, and curd firmness 52.7, 32.4 and 47.0 mm in spring, summer and autumn, respectively. Thus, milk coagulation properties of the milk were lower during summer. There were strong seasonal effects on milk FA proportions, but there were not always changes with progressing season, or changes were different with respect to the impact of the feeding systems (system × season interaction). The milk fat was favourably rich in oleic acid, conjugated linoleic acid and α-linolenic acid and had a low n-6/n-3 fatty acid ratio in all systems. Factors like seasonal variations in grass composition and the energy balance of the cows were considered relevant for the milk FA composition. Overall, seasonal variations in milk quality were less pronounced with part-time grazing with fresh grass indoors as compared to full-time grazing without concentrate.

QUATERNION-TYPE REPRESENTATION FOR MEASURING THE RENNET COAGULATION TIME OF MILK BY COLOR IMAGE SEQUENCES PROCESSING

The determination of the rennet coagulation time of milk by image sequences processing was performed using a computer vision system (CVS), consisting of a computer coupled with a transmitted light microscope equipped with a digital camera. Algorithms implemented with Matlab 2014 encoded the color image as a quaternion, computed and analyzed the histogram peak. The evolution of this last parameter was monitored as a function of the milk coagulation time, for different concentrations of calcium chloride (0.01–0.03 M) and for coagulation temperatures varying between 30 and 36°C. No statistically significant difference was observed in the measurements of the rennet coagulation time, neither by the Berridge method nor by the analysis of the image sequences, except for those at 36°C. The association of the optical microscopic method and the analysis of image sequences by a quaternion-type representation, made it possible to identify optical changes during gel formation and to accurately determine the rennet coagulation time of milk.

СЫРОПРИГОДНОСТЬ МОЛОКА ЧЕРНО-ПЕСТРЫХ КОРОВ С РАЗНЫМИ ГЕНОТИПАМИ КАППА-КАЗЕИНА И ДИАЦИЛГЛИЦЕРОЛ О-АЦИЛТРАНСФЕРАЗЫ

The purpose of the research is improving the quality and technological properties of milk from black-and-white cows. The research was conducted on first-calf cows of a black-and-white breed in LLC «Dusym» of the Atninsky district of the Republic of Tatarstan. Three groups of experimental cows were formed depending on the genotype of CSN3 and DGAT1, which have equal lactation month. Cheese making milk obtained from cows with different allelic variants of the kappa-casein and diacylglycerol O-acyltransferase genes was studied. DNA testing was performed on the CSN3 and DGAT1 genes of experimental cows and allelic variants of these genes were determined by pol-ymerase chain reaction followed by analysis of restriction-site polymorphism. It was found that milk of cows with the genotype CSN3 AB and CSN3 BB, when exposed to rennet, showed a better yield of a dense casein clot (80 and 100%) and separation of serum (P <0.05), with a shorter coagulation time (20.3 and 16.5 min; P <0.05-0.01). Ac-cording to the DGAT1 gene, first-calf milk with the allelic variant DGAT1 AK and DGAT1 KK had the advantage, respectively, 86.7% and 85.7%, 24.0 and 25.7 minutes. The worst milk coagulation time is typical for CSN3 AA group – 29.5 minutes and DGAT1 AA one – 30.4 min. In terms of milk coagulation time, type II (15-40 min.) groups have the genotype CSN3 AB and CSN3 BB with the largest share of cows in the herd – 80.0 and 71.4% and with the genotype DGAT1 AK and DGAT1 KK – 86.6 and 85.7%, respectively. Thus, milk obtained from cows with the kappa-casein gene allele B and the diacylglycerol O-acyltransferase gene allele K gene in the genotype has the best cheese-making properties.

Use of glyoxyl-agarose immobilized ficin extract in milk coagulation: Unexpected importance of the ficin loading on the biocatalysts

A protein extract obtained from fig tree (Ficus carica) latex containing ficin activity was immobilized on glyoxyl agarose. Different biocatalyst loadings were used (3, 10, 30 and 85 mg/g). When casein was used as substrate, the expressed activities were 60%, 58%, 41% and 14%, respectively, very likely due to casein diffusional limitations. As expected, an increase of the concentration of either free or immobilized ficin reduced the clotting time of casein solution and milk. However, maintaining the same amount of ficin, lowly loaded ficin biocatalysts were unable to produce the clotting neither of the casein solutions nor of the milk, while highly loaded catalysts produced a good aggregate. Performing the proteolytic milk treatment at 4 °C to prevent aggregation and them incubating the milk at 40 °C, the use of immobilized enzyme in milk clotting gave coagulum yields of 19%, 24% and 27% for the 10 mg/g, 30 mg/g and 85 mg/g immobilized ficin respectively, while free ficin gave a yield of around 20% under similar ficin concentrations.

Application of some insensitive probiotic lactic acid bacteria and ginger as functional dairy products

The use of dairy-based functional foods has increased markedly over the last fewyears. Ginger is believed to exert a wide range of therapeutic properties. This study aimed toevaluate probiotic properties of twenty Lactic acid bacteria to apply in functional fermented milkfortified with fresh ginger juice to increase the therapeutic and nutritional effects of the product.Ginger juice was prepared from ginger rhizomes through sorting, washing, peeling, crushing andcrude juice extraction. It was assayed for antibacterial activity by minimal inhibitoryconcentration against antibiotic resistant pathogenic bacteria (E. coli BA 12296, Bacillus subtilisDB100, Klebsiella pneumoniaa ATCC12296, Salmonella senftenberg ATCC 8400,Staphylococcus aureus NCTC 10788, Staphylococcus epidermidis ATCC 35984). Total phenol,total flavonoids and antioxidant activity were determined, ginger juice showed an antibacterialactivity and antioxidant activity. Twelve strains out of twenty were resistant to bile saltsconcentrations (0.2, 0.3 and 0.4 w/v), to acid conditions (pH 2.0, 3.0 and 4.0) and were able togrow in the presence of 0.2 and 0.4 w/v of phenol. Seven strains (Lactobacillus delbrueckiisubsp. delbrueckii KT615, Lb. brevis KP653, Lb. delbrueckii subsp. lactis KP645, Lb. plantarumKP623, Lb. paracasei subsp. tolerans WT631, Enterococcus faecalis BM711, Enterococcusfaecium BT734) had the ability to adhere to rabbit intestinal epithelial cells in-vitro, and wereresistant to ginger juice. Ginger juice concentration showed indirect relationship with the milkcoagulation time and direct with syneresis of fermented milk. It was showed that used 2% ofginger juice concentrations was the best results on fermented milk products.

Characterization of the angiotensin-converting enzyme inhibitory activity of fermented milks produced with Lactobacillus casei

Our study assayed angiotensin-converting enzyme (ACE) inhibitory activity and fermentation characteristics of 41 food-originated Lactobacillus casei strains in fermented milk production. Twenty-two of the tested strains produced fermented milks with a high ACE inhibitory activity of over 60%. Two strains (IMAU10408 and IMAU20411) expressing the highest ACE inhibitory activity were selected for further characterization. The heat stability (pasteurization at 63°C for 30 min, 75°C for 25 s, and 85°C for 20 s) and resistance to gastrointestinal proteases (pepsin, trypsinase, and sequential pepsin/trypsinase treatments) of the ACE inhibitory activity in the fermented milks produced with IMAU10408 and IMAU20411 were determined. Interestingly, such activity increased significantly after the heat or protease treatment. Because of the shorter milk coagulation time of L. casei IMAU20411 (vs. IMAU10408), it was selected for optimization experiments for ACE inhibitory activity production. Our results show that fermentation temperature of 37°C, inoculum density of 1 × 106 cfu/g, and fermentation time of 12 h were optimal for maximizing ACE inhibitory activity. Finally, the metabolite profiles of L. casei IMAU20411 after 2 and 42 h of milk fermentation were analyzed by ultra-HPLC electron spray ionization coupled with time-of-flight mass spectrometry. Nine differential abundant metabolites were identified, and 2 of them showed a strong and positive correlation with fermented milk ACE inhibitory activity. To conclude, we have identified a novel ACE inhibitory L. casei strain, which has potential for use as a probiotic in fermented milk production.

A STUDY OF MILK CLOTTING ACTIVITY OF CRUDE GASTRIC RENNET EXTRACTED FROM CAMELS' ABOMASUM AT DIFFERENT AGES

camel rennet was extracted from camel calf stomachs by the method used for bovine rennet. Coagulation of camel milk for the production of cheese has been proved to be difficult by the use of the available commercial rennet. Therefore that study was focused on the use of crude gastric enzymes extracted from different parts stomach at different ages (1, 3 and 5 years old). The non-purified gastric enzymes extracts from camels (GEC) different parts of stomach and at different ages were characterized by their rennin units (RU/g), milk clotting time (Sec.) and proteolytic activities. The conditions of milk clotting by the crude gastric enzymes extracted were optimized at different pH 5.5, 4.5, 4.0, 3.5 and rennin units (RU/g). The results concluded that the extracting solution from the behind part of the stomach was the greatest rennin units (RU/g), milk clotting time (Sec.) and proteolytic activities compared with the extracting solution from the front part of the stomach pH4.5. The good substitute for calves' rennet can be obtained from the dried vells of camel and can be named adult camel rennet.

Estimation of coagulation time in cheese manufacture using an ultrasonic pulse-echo technique

The essential parameter in the cheese-making industry is the coagulation time because it marks the end point of the enzymatic phase and the start point of the aggregation. Furthermore, it is used to evaluate the cutting time that characterizes the time at which curd is cut. This paper proposes a non-destructive ultrasonic pulse-echo to monitor in real-time the acoustic impedance of milk during cheese manufacturing in order to predict the coagulation time. The evolution of the acoustic impedance is going through two phases the enzymatic phase and the aggregation phase. The transition point between these two phases defines the milk coagulation time. Three rennet concentrations and three temperatures were considered in our experiments to study the effect of these factors on coagulating milk. The experimental results prove that our proposed method determines the coagulation time with efficiency, and it is more simple compared with our previous work in which the phase velocity was used to determine the milk coagulation time.

Prediction of milk coagulation time using an ultrasonic experimental and theoretical method based on Argand diagram

A non-destructive ultrasonic method is proposed to control the rennet-induced coagulation of milk during cheese production based on the Argand diagram. The evolution of the resonance width of a plate immersed in the milk during coagulation determines the coagulation time. Based on the Argand diagram the resonance width evolves over two steps easily identifiable, corresponding to the stages of coagulation. It increases to a maximum and then it decreases over time during the enzymatic coagulation of milk, under three levels of temperature and three levels of rennet concentration. This maximum identifies the coagulation time. The experimental results and theoretical model agree closely with each other and proves the effectiveness of our proposed method.

Influence of feeding Murciano-Granadina Goats with Posidonia oceanica Banquettes on the Resulting Milk and Cheese

The inclusion in the diet of biological products of a biodegradable nature is a highly valued strategy with many advantages. Posidonia oceanica is a seagrass species which may be used as a substitute for straw. In this study, one group of goats (control) was fed a normal diet that contained straw, while the straw in the diet of the other group was replaced by P. oceanica. No significant differences were found between the control and experimental group regarding the main physicochemical and sensorial parameters of the resulting milk and cheese; although the cheese from the group fed P. oceanica was firmer and chewier. When the milk-clotting time was determined under different assay conditions, the origin of the milk was found to have a significant effect, the milk from animals fed with algae showing greater technological suitability. In conclusion, P. oceanica can be used as a straw substitute, promoting a sustainable livestock system and contributing to the maintenance of meadows.

EFFECT OF STORAGE TEMPERATURES ON CHEMICAL, MICROBIOLOGICAL AND SENSORY PROPERTIES OF RENNET EXTRACTED BY SOAKING AND MECHANICAL PROCESSES

A comparison was done among rennet samples extracted from different forms of calves vells (fresh and dried) (sliced or minced) by using soaking and mechanical processes, during storage at room temperature (25-30 o C) and refrigeration +- 5o C) for 90 days. The resultant rennet solutions were tested for milk clotting time (MCT), rennet activity (total rennin units/gram (RU/g), rat of loss % of rennet activity or rennet stability, microbiological assessments and sensory properties. Results show that storage temperature had a highly significant effect on all treatments and led to a continuous decrease in RU/g, yield and the keeping quality of all forms of vells at both temperatures. After 90 days of storage, protective effect and stability of rennet activity were superior when storage was carried out in refrigerator, almost double clotting actively of rennet and an increase in the shelf-life of. The average of rennet actively and rat of activity loss were 107.25 RU/g and 14.96 % respectively, with the storage at refrigerator, whereas the average of the other ones stored at room temp. were 94.04 RU/g and 25.41 % in order. T1 with of dried sliced vells kept at refrigerator had the highest rate of stability (119.62 RU/g), while T3 of fresh minced vells stored at room temperature had the lowest one (95.84 RU/g). T3 of fresh sliced vells stored at room temperatures had the highest rate of activity loss (36.51 %), while C soaking treatment of dried sliced vells stored at room temperature recorded the lowest rate of activity loss (10.28 %). Results show also that the mechanical process was superior than the soaking one and stirring at 100 rpm.(T1) was the perfect treatment for extraction. Microbiologically results revealed that initial bacterial counts (TBC) in all treatments, ranged between 104 to 106. C of all treatments had the lowest TBC followed by T1, T2 and T3 in order. Dried sliced vells recorded the lowest TBC followed by dried minced, fresh sliced and fresh minced vells respectively. No growth of coliform bacteria was detected in all treatments, along the storage period. Yeasts & moulds were absent in C and T1 treatments while appeared in case of T2 and T3treatments. Results of sensory evaluation show considerable differences among treatments. C and T1 were found the best ones, characterized by brown, unique odor, clear and free from sediments.

Milk Coagulation Properties and Milk Protein Genetic Variants of Three Cattle Breeds/Types in Sri Lanka

Milk coagulation is the primary step in the development of most dairy products. Raw milk from individual cows and different breeds exhibit distinct coagulation capacities. This variation is largely influenced by milk protein genetic variants. The aim of the present study was to evaluate differences in coagulation properties between milk obtained from three cattle breeds/types found in Sri Lanka. A total of 90 milk samples (400mL from each individual) were collected from two Sri Lankan cattle breeds/types (Thamankaduwa White/TW and Local/“Batu” cattle) and one European cattle breed (Friesian). Collected samples were subjected to enzymatic coagulation using commercial rennet source (Chymax®, Christian Hansen Standard, Denmark) and lactic acid bacteria (LAB) coagulation using a commercial starter culture(YFL 8 12,Christian Hansen Standard, Denmark) to determine milk coagulation properties. Different properties of milk coagulum such as yield, curd firmness, syneresis and rheological properties were evaluated. The biochemical composition (lactose, protein, fat, solid-non-fat) of milk samples were determined. Capillary Zone Electrophoresis (CZE) method was used to determine milk protein genetic variants. Experimental design was Nested Completely Randomized Design with three treatments. Milk coagulation time and curd firmness after enzymatic-coagulation were not significantly different (p>0.05) among the breeds. Coagulum yield was significantly higher (p<0.05) for the TW type than that of other breeds. Coagulum yield was negatively correlated with β-caseinA1 and α-lactalbumin in both enzymatic (-0.58) and LAB coagulation (-0.69). Coagulum yield was positively correlated (p<0.05) with β-casein B variant (0.70), protein (0.34) and lactose (0.36) contents. Meltability value was weakly and positively (p<0.05) correlated (0.34) with fat content of milk. Overall results indicate that there is a significant correlation between milk coagulation properties and milk protein genetic variants in three cattle breeds/types considered in the current study. TW type is the unique among studied breeds in terms of coagulation properties and milk protein genetic variants.

Role of different sources of dietary PUFA supplementation on sheep welfare under high ambient temperature

The purpose of this study was to evaluate the effects of different sources of polyunsaturated fatty acids (PUFA) supplemented in the diet on the welfare of lactating sheep exposed to high ambient temperature. The experiment was conducted during summer, it involved 32 ewes divided into 4 groups, and lasted 6 weeks. All groups were fed twice daily and received 1.8kg/ewe/d of oat hay. The control group also received 1kg/ewe/d of pelleted concentrate, whereas ewes in the experimental groups were supplemented with whole flaxseed (FS), seaweed Ascophyllum nodosum (Tasco®, AG), or their combination (FS+AG). At the beginning of the experiment, and weekly thereafter, the respiration rate, rectal temperature, body condition score (BCS) and body weight of the ewes were recorded. Milk samples were collected from each ewe weekly for the determination of the chemical composition, somatic cell count, and coagulating properties. Milk samples were also analyzed for their concentration of plasmin. Flaxseed diet during heat stress resulted in a reduction of the respiration rate, and in an increase of both milk and fat yield. The PUFA in the combined diet influenced the rectal temperature, and the respiration rate; also the milk yield and the concentration of plasmin (PL) increased in FS+AG diet. The lowest value of BCS recorded in ewes receiving the AG diet together with a rise in the respiration rate and rectal temperature suggested poor sheep welfare. Furthermore, sheep receiving the AG diet showed a consistent increase in the milk PL concentration that was responsible of the increase of milk clotting time and rate of clot formation.

AVALIAÇÃO DA QUALIDADE DE MAMÕES (CARICA PAPAYA L.)

This study aimed to evaluate the quality of 3 groups of papaya at different ripening stages (green, ripe and overripe) considering 3 parts of the fruit (skin, pulp and seed). Fruit were separated into 3 groups (green, ripe and overripe), with 4 replications of 3 fruit each, for physical and chemical analysis of skin, pulp and seed. The total titratable acidity was higher in the pulp and seeds of green papaya and in the skin of ripe papaya. Higher pH values were found in the pulp of ripe and overripe papaya, in the seed of the overripe papaya and in the skin of green and overripe papaya. The highest percentage of water was verified in the pulp of green papaya, in the seed of ripe and overripe papaya and in the skin of ripe papaya. The total soluble solids were found at greater amounts in the pulp of overripe papaya, in the seed of ripe and overripe papaya and in the skin of ripe papaya. The Biuret test indicated that the seeds of all papayas contained the highest concentration of protein. The coagulation test was more effective for the pulp of green papaya and the skin of green and overripe papaya, as these parts presented the shortest milk-clotting time, indicating that the enzymes in these parts have a greater ability to break down the protein structures.