Seasonal changes in the technological and compositional quality of ewe's raw milks from commercial flocks under part-time grazing

Abstract

Rennet coagulation parameters, curd texture and gross compositional variables were studied in ewes' raw milk samples from nine commercial flocks using different concentrate:forage ratios and grazing times. From early lactation to March flocks were fed concentrate pellets and hay whereas from April to the end of lactation flocks were allowed to graze from 6 to 19 h/day receiving concentrate supplementation in the morning and evening. Milk from late-lactation flocks, when allowed to graze, showed higher content of fat, dry matter, protein, casein, soluble protein, total calcium, curd firmness and curd resistance to compression than the milk from early lactation flocks. Higher total calcium content and lower fat content were found when the early lactation flocks were fed high concentrate:forage ratio than when the flocks were fed low ratio. Curd firmness were lower for milk from flocks fed high concentrate:forage ratio, and the curd resistance to compression was greater, than for milk from flocks fed low ratio. At late lactation, when flocks grazed for a long time per day the total calcium content was higher than when the flocks grazed for a short time per day. Principal component analysis showed that protein and fat content were highly correlated with coagulum and curd firmness, whereas total calcium content was highly correlated with curd resistance to compression, and milk pH with rennet coagulation time.

Characterization of curd grain size and shape by 2-dimensional image analysis during the cheesemaking process in artisanal sheep dairies

“…Therefore, due to the difficulty of controlling these wide variations, the cheesemakers make the decision to start the cutting process according to the sensory observation of the curd consistency, which implied that coagulation time varied from 24 to 55 min. Previous studies using raw milk from commercial flocks showed that curd firmness (curd resistance to compression) at cutting point varied from approximately 82 to 115 g during Idiazabal cheese processing season (Nájera et al, 2009;Abilleira et al, 2010). As expected, all cheesemakers used a coagulation temperature close to 30°C, and we found very few significant (P ≤ 0.05) differences for curd pH among artisanal dairies (mean pH values ranged between 6.49 and 6.65).…”

Relationships between cheese-processing conditions and curd and cheese properties to improve the yield of Idiazabal cheese made in small artisan dairies: A multivariate approach

“…For the measurement of gel-compression work at cutting point, milk coagulation conditions (pH, temperature, rennet concentration, and time until curd cutting point) used during the cheese manufacturing were simulated in the laboratory using the raw milk and rennet paste collected in the small dairies on the same day. A compression-extrusion test was carried out using a texture analyzer (TA-XT2i; Stable Micro Systems, Godalming, UK) armed with a 5-kg load cell and a 25-mm diameter cylindrical probe (Nájera et al, 2009). Milk and rennet were poured into a plastic container (28-mm diameter), and after clotting simulated the real conditions, the test was carried out using a test speed of 2 mm/s and a penetration length of 10 mm.…”

Part-time grazing improves sheep milk production and its nutritional characteristics

“…Textural measurement of the curds was made using a Texture Analyser TA-XT2i (Stable Micro Systems, Surrey, UK) as described previously by Nájera et al (2009).…”