The knowledge of detailed composition of milk protein fractions is important for dairy goat industry because of its impact on technological properties of milk and the nutritional value of milk and dairy products. The caseins (αs1-, αs2-, β- e κ-casein) and whey proteins (α-lactalbumin, β -lactoglobulin) are the same as in bovine milk but their genetic variants are different because of different polymorphisms at these loci. The aim of this study was to quantify the protein fractions and concurrently to identify their genetic variants developing a method based on Reverse-Phase High Performance Liquid Chromatography (RP-HPLC). This project involved 1,272 goats from 6 different breeds reared in 35 farms located in Sardinia (Italy). Individual milk samples were analysed for milk composition, coagulation, curd firming and syneresis, cheese yield and milk nutrients recovery in curd. To quantify the content of protein fractions of different genetic variants, freeze-dried protein samples of milk previously genotyped for genetic variants were used for calibration of HPLC since commercial standards are not available for goat milk. Five variants of αs1-casein (A, B, E, F and null; CSN1S1 gene; 11 genotypes), 2 variants of αs2-casein (A/F and C; CSN1S2 gene; 3 genotypes), 3 variants for β-casein (A, C, and null; CSN2 gene; 4 genotypes) and 5 variants for κ-casein (A, B, C, D, and null; CSN3 gene; 8 genotypes) were identified and quantified by HPLC. The statistical analysis of preliminary data revealed that polymorphisms in goat milk proteins have strong effects on the concentration of different caseins and on milk coagulation, curd firming, cheese yield and nutrient recovery traits. Moreover, we confirmed that different goat breeds are characterised by different genotypes frequencies, which are associated to different amounts and proportions of caseins in milk. These results provided useful information for defining the value of dairy goat industry and for breeding programs aimed at improving goat milk quality and technological characteristics.
Quantifying and genotyping protein fractions in milk of different goat breeds by RP-HPLC
G. Secchi;N. Amalfitano;S. Pegolo;A. Cecchinato;G. Bittante
2020
Abstract
The knowledge of detailed composition of milk protein fractions is important for dairy goat industry because of its impact on technological properties of milk and the nutritional value of milk and dairy products. The caseins (αs1-, αs2-, β- e κ-casein) and whey proteins (α-lactalbumin, β -lactoglobulin) are the same as in bovine milk but their genetic variants are different because of different polymorphisms at these loci. The aim of this study was to quantify the protein fractions and concurrently to identify their genetic variants developing a method based on Reverse-Phase High Performance Liquid Chromatography (RP-HPLC). This project involved 1,272 goats from 6 different breeds reared in 35 farms located in Sardinia (Italy). Individual milk samples were analysed for milk composition, coagulation, curd firming and syneresis, cheese yield and milk nutrients recovery in curd. To quantify the content of protein fractions of different genetic variants, freeze-dried protein samples of milk previously genotyped for genetic variants were used for calibration of HPLC since commercial standards are not available for goat milk. Five variants of αs1-casein (A, B, E, F and null; CSN1S1 gene; 11 genotypes), 2 variants of αs2-casein (A/F and C; CSN1S2 gene; 3 genotypes), 3 variants for β-casein (A, C, and null; CSN2 gene; 4 genotypes) and 5 variants for κ-casein (A, B, C, D, and null; CSN3 gene; 8 genotypes) were identified and quantified by HPLC. The statistical analysis of preliminary data revealed that polymorphisms in goat milk proteins have strong effects on the concentration of different caseins and on milk coagulation, curd firming, cheese yield and nutrient recovery traits. Moreover, we confirmed that different goat breeds are characterised by different genotypes frequencies, which are associated to different amounts and proportions of caseins in milk. These results provided useful information for defining the value of dairy goat industry and for breeding programs aimed at improving goat milk quality and technological characteristics.Pubblicazioni consigliate
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