Based on the potential benefits to long-term human health there is interest in developing sustainable nutritional strategies for reducing saturated and increasing specific unsaturated fatty acids in ruminant milk. The impact of plant oil supplements to diets containing different forages on caprine milk fatty acid composition was examined in two experiments using twenty-seven Alpine goats in replicated 3 × 3 Latin squares with 28 d experimental periods. Treatments comprised of no oil (control) or 130 g/d of sunflower-seed oil (SO) or linseed oil (LO) supplements added to diets based on grass hay (H; experiment 1) or maize silage (M; experiment 2). Milk fat content was enhanced (P < 0·01) on HSO, HLO and MLO compared with the corresponding H or M control diets, resulting in 17, 15 and 14 % increases in milk fat secretion, respectively. For both experiments, plant oils decreased (P < 0·05) milk 10 : 0–16 : 0 and odd- and branched-chain fatty acid content and increased 18 : 0, trans-Δ6–9,11–14,16-18 : 1 (and their corresponding Δ-9 desaturase products), trans-7, trans-9-conjugated linoleic acid (CLA), trans-9, trans-11-CLA and trans-8, cis-10-CLA concentrations. Alterations in the distribution of cis-18 : 1, trans-18 : 1, -18 : 2 and CLA isomers in milk fat were related to plant oil composition and forage in the diet. In conclusion, plant oils represent an effective strategy for altering the fatty acid composition of caprine milk, with evidence that the basal diet is an important determinant of ruminal unsaturated fatty acid metabolism in the goat.

Sediment formation was investigated during UHT treatment of goats' milk, subjected to indirect treatment at 140°C for 2 s, with upstream homogenisation. Stabilisers evaluated were sodium hexametaphosphate (SHMP), trisodium citrate (TSC), disodium hydrogen orthophosphate (DSHP), and sodium dihydrogen orthophosphate (SDHP). With no added stabiliser, goats' milk produced a heavy sediment on UHT treatment. Addition of SDHP reduced pH, had little effect on ionic calcium and did not substantially reduce sediment. However, addition of SHMP, DSHP and TSC each reduced ionic calcium, increased ethanol stability and reduced sediment. Following stabiliser additions, there was a good correlation between ethanol stability and ionic calcium (R2=0·85) but not between ethanol stability and pH (R2=0·08). Overall, reducing ionic calcium reduced the amount of sediment formed for all these three stabilisers, although there was no single trend line between sediment formation and ionic calcium concentration. Sediment formation was not well correlated with pH for TSC or for SHMP, but it was for DSHP, making it the only stabiliser where sediment formation correlated well both with ionic calcium and pH, which might account for its effectiveness at higher ionic calcium levels. Sediment was much reduced when the temperature was reduced from 140°C to 125°C and 114°C. There were no further changes in sediment on storage for two weeks. Analysis of the sediment showed that it was predominantly fat and protein, with a mass ratio ranging between 1·43:1 and 1·67:1. Its mineral content was usually less than 5% of dry weight. The maximum amounts of P and Ca were found to be 2·32% and 1·63%, respectively.

Two monoclonal antibodies (MAb) raised against bovine κ-casein were developed and applied in an automated optical biosensor (Biacore 3000) to create easy and fast direct and inhibition biosensor immunoassays (BIA) for the detection of cows' milk in the milk of ewes and goats. With both assay formats, low limits of detection (<0·1%) and fast run times (around 5 min) were obtained. For sample preparation, milk was diluted in buffer (direct assay) or in an antibody-containing buffer (inhibition assay) only. For quantitative analysis, calibrants of cows' milk in ewes' or goats' milk were used. Advantages of the direct BIA are: the single reagent format (biosensor chip immobilized antibodies only); the use of small amounts of antibodies (2 μg for >350 tests); and the wide measurement range (0·1 to 10% cows' milk). Despite these advantages, the inhibition BIA (using κ-casein immobilized on the chip) was preferred because of the possible application of non-purified Mab, the higher responses, the higher sensitivity at relevant low percentages of cows' milk and its robustness (>800 cycles per chip).

A kinetic model was proposed for describing the curd assembly of skimmed goats' milk during enzymic coagulation. The enzymic coagulation of milk was monitored using an optical sensor that measured diffuse reflectance (light backscatter) at 880 nm. The appearance of a shoulder, at low temperatures and protein concentrations, in the diffuse reflectance ratio profile after the inflection point of the curve (Tmax) appeared to separate the aggregation and curd firming steps. The diffuse reflectance ratio profile after Tmax was attributed to the overlapping of casein micelles aggregation and curd firming reactions. The developed kinetic model combined a second order reaction model to describe aggregation reactions and a first order reaction model to describe firming processes reactions. A completely randomised block design with three replications was used to determine the effect of protein concentration and temperature on kinetic constants. Milk was adjusted to three levels of protein (30, 50 and 70 g/kg), and coagulated at five temperatures (20, 25, 30, 35 and 40°C) to test a wide range of processing conditions. Data points from each profile after Tmax were fitted to the proposed model using non-linear regression. The average R2 and standard error of prediction (SEP) for 45 tests conducted were in the range of 0·9975±0·0027 and 0·0081±0·0037, respectively. A significant increase in characteristic times for aggregation (τ2) and curd firming processes (τ1) were found when temperature decreased or protein increased. Theoretical asymptotic value of reflectance ratio, R∞, increased with increasing level of protein and temperature (P<0·05). The parameter β1, which represented the fraction of diffuse reflectance ratio attributed to aggregation, decreased with increasing temperature and decreasing protein.

We analysed the effects of goats' milk (GM) on the nutritive utilization of Ca and P in rats with resection of 50% distal small intestine in comparison with cows' milk (CM) and a standard non-milk diet. The three test diets contained 200 g protein and 100 g fat/kg. The apparent digestibility coefficient (ADC) of Ca and P were considerably higher in the two groups of rats given the GM diet than those given the other two diets. Ca and P retention did not decrease by effect of intestinal resection with GM diet. In both groups of animals, serum Ca and P levels and ionic Ca were higher in the case of the GM diet than the other two diets, whereas the parathyroid hormone levels were lower. Ca content in femur, sternum and longissimus dorsi muscle was higher in rats given the GM diet. P content in femur and sternum was higher among the two groups of rats given a milk-based diet (GM or CM), especially with GM diet. The GM diet has beneficial effects on nutritive utilization of Ca and P in control rats and those with resection of the distal small intestine.

An objective method for determining the coagulum cutting time is needed to improve consistency and processing efficiency of goats' cheese. A fibre optic sensor was used to measure the backscatter of near-infrared radiation at 880 nm during the coagulation of skimmed goats' milk for the purpose of predicting coagulum cutting time. A randomised block design, replicated three times, was used to test the effect of three protein concentrations (3, 5 and 7% (w/w)) on diffuse reflectance parameters for cutting time prediction of milk coagulated at five different temperatures (20, 25, 30, 35 and 40°C) to assure a wide range of coagulation rates. The inclusion of a protein term in the existing algorithms was essential to reduce the standard error of prediction to under 6·2 min. An algorithm including a time-based parameter and a protein term, Tcut=β0T2 min (1+γ% Protein) was found to predict cutting time with a SEP of 2·42 min and an R2 of 0·98. γ was considered constant (γ=−0·0674, goats' milk) representing the protein effect on β0. Algorithms using response-based parameters (such as change in reflectance ratio) and the composition parameter protein required additional regression parameters such as temperature and an intercept term to predict the cutting time with the same precision as algorithms using only time-based parameters. Time-based parameters were found to decrease proportionally with increasing temperature and decreasing protein concentration. Response-based and mixed-based parameters were found to decrease with decreasing temperature. Reflectance ratio at cutting time did not significantly change with protein concentration for skimmed goats' milk. The activation energy of κ-casein hydrolysis was calculated based on changes in reflectance profile parameters and was found to be in the range 63–72 kJ mol−1.

A new polymerase chain reaction (PCR)-based method was developed to detect cows' milk in goat cheese. This method is based on mitochondrial DNA (mtDNA) control region sequence variations. DNA extractions from 150 mg of cheese were carried out using a spin column-based method. Subsequent PCR amplifications of DNA were performed with cow specific primers, demonstrating the ability to detect cows' milk in a variety of cheeses. This simple approach provides high quality DNA, and is shown to be very sensitive, with a detection limit of less than 0·1% of cows' milk. Analysis of an agarose gel digital image allows a rough estimation of the percentage of cows' milk used in adulteration.

Polymorphism in the goat kappa casein gene was studied using the base excision sequence scanning (BESS) method and sequencing. Seven polymorphic sites, corresponding to single nucleotide transversions were detected. Three of these were silent mutations while the other four produced amino acid substitutions. The association between these polymorphic sites was investigated, which resulted in the identification of three goat kappa casein alleles, designated A, B, and C. Protocols for rapid genotyping of the C variant were developed by polymerase chain reaction–restriction fragment length polymorphism using Alw44I and BseNI restriction endonucleases. The occurrence of this allele was found to be very low in Spanish breeds but more frequent in the French Saanen goat. Further studies among different goat populations are necessary to establish the distribution of these alleles and their effects on the quality and functional properties of milk.