Milk from cows of different β-casein genotypes as a source of β-casomorphin-7

Abstract

The aim of this study was to quantify β-casomorphin-7 in raw, hydrolyzed and processed milk in different stages of the cow lactation. The obtained results lead to the following conclusion: the highest amount of β-casomorphin-7 released from the hydrolyzed and processed milk is related to the β-casein A1 allele, irrespective of a lactation period. Some traces of β-casomorphin-7 in milk from cows with the β-casein A2 variant are probably a result of the acid hydrolysis of β-casein during its digestion with pepsin. It has been shown that processing of raw milk at high temperatures affects, in a slight degree, the differences between β-casomorphins-7 originating from different β-casein genotypes. The obtained results suggest a possibility to provide a new nutritional factor for milk quality based on the content of β-casomorphin-7 liberated in vivo from milk digested by a mixture of the gastrointestinal enzymes.

Formation and Degradation of Beta-casomorphins in Dairy Processing

“…One alternative method for BCMs determination is ELISA (Sienkiewicz-Sz»apka et al, 2009;Cieslinska et al, 2012). Using ELISA, levels of BCM7 and BCM5 in cheese as low as 0.04 and 0.05 mg/g, respectively, could be accurately quantified.…”

“…So high levels of somatic cell may degrade BCM7; but this needs further investigation. Similarly, Cieslinska et al (2012) investigated the presence of BCM7 in bovine milk collected from healthy cows which did not indicate any subclinical symptom of mastitis and showed that BCM7 was detected in all milk samples with the highest amount in A1 milk, followed by A1A2 milk and A2 milk. Surprisingly, BCM7 was found in the milk containing the A1 variant but also in A2 variant-containing milk.…”

“…The authors showed that BCM7 was not detected in these products, even though the products contained A1 and B b-casein variants which contain the BCM7 sequence. Similarly, Cieslinska et al (2012) quantified the content of BCM7 by ELISA in varieties of milk containing pure A1, A2 and mixture of A1 and A2 b-casein variants after pasteurization (95 C/20 minutes) and sterilization (117 C/5 minutes). BCM7 content tended to decrease after heating of the milk but not due to the breaking down the peptide bonds of BCM7 but because of the reaction between lactose and amino acids residues of BCM7, which reduced the binding affinity of the modified BCM7 to the antibody used in the ELISA assay, leading to underestimated results for BCM7 levels (Cieslinska et al, 2012).…”

“…The BCM7 peptide has been identified in raw milk Cieslinska et al, 2012) and some cheeses (Jarmolowska et al, 1999;De Noni and Cattaneo, 2010), but was not found in commercial yoghurt (Kahala et al, 1993;Schieber and Br€ uckner, 2000;De Noni and Cattaneo, 2010). Whether BCMs do form and the amount of BCM forming at different processing steps needs further investigation and possibly will depend on the heat treatment and fermentation process but remains an intriguing unknown.…”

“…Nowadays, at the forefront of detection techniques, is mass spectrometry coupled to electrospray ionization (ESI) which is by far the most reliable detection technique for small peptides (De Noni and Cattaneo, 2010). Alternatively, enzyme-linked immunosorbent assay (ELISA) has been applied to detect and quantify BCMs in dairy products (Sienkiewicz-Sz»apka et al, 2009;Cieslinska et al, 2012).…”