A2A2 milk: Brazilian consumers’ opinions and effect on sensory characteristics of Petit Suisse and Minas cheeses

A discussion on A1-free milk: Nuances and comments beyond implications to the health

This chapter provides an overarching view of the multifaceted aspects of milk β-casein, focusing on its genetic variants A1 and A2. The work examines the current landscape of A1-free milk versus regular milk, delving into health considerations, protein detection methods, technological impacts on dairy production, non-bovine protein, and potential avenues for future research. Firstly, it discussed ongoing debates surrounding categorizing milk based on A1 and A2 β-casein variants, highlighting challenges in establishing clear regulatory standards and quality control methods. The chapter also addressed the molecular distinction between A1 and A2 variants at position 67 of the amino acid chain. This trait affects protein conformation, casein micelle properties, and enzymatic susceptibility. Variations in β-casein across animal species are acknowledged, casting doubt on non-bovine claims of "A2-like" milk due to terminology and genetic differences. Lastly, this work explores the burgeoning field of biotechnology in milk production.

Multi-attribute temporal descriptive methods in sensory analysis applied in food science: A systematic scoping review

Among descriptive sensory evaluation methods, temporal methods have a wide audience in food science because they make it possible to follow perception as close as possible to the moment when sensations are perceived. The aim of this work was to describe 30 years of research involving temporal methods by mapping the scientific literature using a systematic scoping review. Thus, 363 research articles found from a search in Scopus and Web of Science from 1991 to 2022 were included. The extracted data included information on the implementation of studies referring to the use of temporal methods (details related to subjects, products, descriptors, research design, data analysis, etc.), reasons why they were used and the conclusions they allowed to be drawn. Metadata analysis and critical appraisal were also carried out. A quantitative and qualitative synthesis of the results allowed the identification of trends in the way in which the methods were developed, refined, and disseminated. Overall, a large heterogeneity was noted in the way in which the temporal measurements were carried out and the results presented. Some critical research gaps in establishing the validity and reliability of temporal methods have also been identified. They were mostly related to the details of implementation of the methods (e.g., almost no justification for the number of consumers included in the studies, absence of report on panel repeatability) and data analysis (e.g., prevalence of use of exploratory data analysis, only 20% of studies using confirmatory analyses considering the dynamic nature of the data). These results suggest the need for general guidelines on how to implement the method, analyze and interpret data, and report the results. Thus, a template and checklist for reporting data and results were proposed to help increase the quality of future research.

Kappa and beta-casein alleles in dairy zebu cattle

The kappa (CSN3) and beta-casein (CSN2) genes are intensively genotyped in dairy cattle for selection purposes. This information is also generated and disseminated for Zebu breeds adapted to tropical climates. The objective of this work was to gather information on the genotypes for the CSN3 and CSN2 genes in three breeds (Gyr, Guzerat and Sindhi), and to verify the genotypic frequencies in the populations. The genotype AA and allele A frequencies are high for the CSN3 gene, without changes in values over the years, possibly indicating a small gene participation in traits under selection. In addition, the A2A2 frequencies are high for the CSN2 gene (<∼0.80). It is recommended to verify the association and contribution of CSN3 genotypes in productive traits for these breeds. The potential of A2 milk production by these genetic groups is also confirmed.

Worldwide research on the health effects of bovine milk containing A1 and A2 β-casein: Unraveling the current scenario and future trends through bibliometrics and text mining

The possible adverse effect of consuming bovine milk with A1 β-casein (but not with A2 β-casein) on health aspects due to the release of β-casomorphin-7 (BCM-7) is currently under debate. The aim of this study was to perform a bibliometric analysis of studies extracted from Scopus to explore the relationship between BCM-7, A1 or A2 bovine milk with different aspects of health. Over time, several research groups were formed that are no longer active and although some authors have returned to the field of study, they have focused their efforts mainly on conducting reviews that show the same imprecise conclusions due to the few original articles. Research is concentrated in Europe and Asia, where New Zealand, China and Germany are the countries with the most publications, records and citations on the subject, respectively. On the other hand, no country in Africa or South America has scientific production, which opens the possibility of building collaborations between countries and exploring areas that lack scientific studies. Based on conflicting information from primarily in vitro and animal studies, and limited clinical trials with poor designs, A1 milk presents pro-inflammatory and oxidative activity, but the evidence is insufficient to associate its consumption with negative health effects. However, A2 milk may be better tolerated by the digestive system of some individuals, suggesting its possible modulating role in the intestinal microbiota. Stronger scientific evidence is needed to reach a consensus on whether the presence of β-casein A1 can significantly negatively affect health. The information shown will allow a better understanding of the subject and consumers will be able to make their own decisions regarding A1 or A2 milk.

What is the impact of amino acid mutations in the primary structure of caseins on the composition and functionality of milk and dairy products?

The impact of amino acid mutations within the peptide structure of bovine milk protein is important to understand as it can effect processability and subsequently effect its physiological properties. Genetic polymorphisms of bovine caseins can influence the chemical, structural, and technological properties, including casein micelle morphology, calcium distribution, network creation upon gelation, and surface activity. The A1 and A2 genetic variants of β-casein have recently acquired growing attention from both academia and industry, prompting new developments in the area. The difference between these two genetic variants is the inclusion of either proline in β-casein A2 or histidine in β-casein A1 at position 67 in the peptide chain. The aim of this review was to examine the extent to which milk and ingredient functionality is influenced by β-casein phenotype. One of the main findings of this review was although β-casein A1 was found to be the dominant variant in milks with superior acid gelation and rennet coagulation properties, milks comprised of β-casein A2 possessed greater emulsion and foam formation capabilities. The difference in the casein micelle assembly, hydrophobicity, and chaperone activity of caseins may explain the contrast in the functionality of milks containing β-casein from either A1 or A2 families. This review provides new insights into the subtle variations in the physicochemical properties of bovine milks, which could potentially support dairy producers in the development of new dairy products with different functional properties.

•

Impact of β- and other caseins on the casein micelle structure and functionality.

•

Proline and histidine in β-caseins play a key role in casein micelle conformation.

•

Chaperone activity of β-casein A2 towards heat-induced aggregation of whey protein.

•

Gels prepared of milks with β-casein A1 possess a denser and firmer structure.

•

Ordered structure of β-casein A2 led to improved emulsion and foam formation.

A2 Milk: New Perspectives for Food Technology and Human Health

Although milk consumption is increasing worldwide, in some geographical regions, its consumption has persistently declined in recent decades. This fact, together with the increase in milk production prices, has caused both milk producers and the dairy industry to be immersed in a major crisis. Some possible solutions to this problem are to get people who do not currently consume milk to start drinking it again, or to market milk and dairy products with a higher added value. In this context, a type of milk called A2 has recently received attention from the industry. This type of milk, characterized by a difference in an amino acid at position 67 of the β-casein polypeptide chain, releases much smaller amounts of bioactive opioid peptide β-casomorphin 7 upon digestion, which has been linked to harmful effects on human health. Additionally, A2 milk has been attributed worse technological properties in the production of some dairy products. Thus, doubts exist about the convenience for the dairy industry to bet on this product. The aim of this review is to provide an update on the effects on human health of A2 milk, as well as its different technological properties to produce dairy products.

Novel LNA probe-based assay for the A1 and A2 identification of β-casein gene in milk samples

•

A novel LNA probe-based qPCR allowed the detection of A1 and A2 alleles from β -casein gene in bovine samples.

•

100% of agreement between results obtained by rHamp and LNA qPCR assays.

•

The limit of detection of A1 in A2 samples was 1% or 7.5 DNA copies.

•

This method is a highly sensitive and specific tool for detecting A1 and A2 alleles directly in milk.

The rising consumption of A2 milk and its derivatives in recent years has garnered attention from both consumers and producers, mainly due its possible health benefits, such as enhanced digestion and easier absorption. Thus, a novel real-time PCR using a combination of locked nucleic acid modified (LNA) conjugated probes was developed to genotype A1 and A2 alleles of β-casein gene (CSN2) and to detect and quantify the A1 presence in A2 samples. The limit of detection for each probe (A1 and A2) was evaluated using decreasing serial dilutions. Besides, the sensitivity of A1 allele detection in the A2 samples was also tested. The limits of detection of A1 and A2 alleles were 6 copies, while for A1 allele detection in A2 samples was 7.5 copies (1%). The LNA-probe based method was found to be rapid, robust, highly sensitive, cost effective, and can be employed as screening test to certificate the A2 dairy products.

"A2 milk" authentication using isoelectric focusing and different PCR techniques

Genetic variants of milk proteins have attracted great interest for decades as they are related to important issues such as the composition and technological properties of milk. More recently, an "A1/A2 hypothesis" was developed saying that β-casein variant A1 may be a dietary risk factor for cardiovascular diseases, type 1 diabetes, sudden infant death syndrome and neurological disorders due to the release of β-casomorphin-7, whereas no evidence for such adverse effects was assumed for β-casein A2. Thus, the aim of this study was to adapt and establish analytical methods for the identification of genetic variants of β-casein using isoelectric focusing of milk proteins as well as appropriate PCR techniques. Allele-specific polymerase chain reaction (AS-PCR) proved to be a reliable method for differentiating most common β-casein variants (A1, A2, B, C), amplification-created restriction site (ACRS)-PCR using three different restriction enzymes allowed also the detection of variant A3, and the restriction fragment length polymorphism (RFLP)-PCR method enabled the reliable discrimination between A2 (homozygote/heterozygote) and non-A2 animals. Since traces of β-casein A1 were also found in commercial "A2 milk" in Austria, the authentication of such expensive dairy products is urgently recommended, both by genotyping of all dairy cows at farm level (to confirm that all cows are homozygous β-casein A2A2) and by screening commercial products on the market (to confirm the absence of β-casein variants A1, B, and C in dairy products labelled "A2 milk") to protect consumers from this unexpected fraud.

Guzerat indicine cattle and A2 milk production

Cow milk might be associated to gastrointestinal disorders and abdominal pain in some people, which are, in part, due to the digestion of A1 beta-casein. Within this context, A2 milk has emerged as an alternative since it only contains A2 beta-casein that does not cause these complications. This milk is produced by cows with the A2A2 genotype. The aim of this study was to investigate the allele and genotype frequencies for the beta-casein gene in Guzerat cattle and to evaluate the feasibility of selection and production of A2 milk. The genotypes of 283 Guzerat cows from 10 herds were analyzed. The frequency of the A2A2 genotype was 0.80 and the frequency of the A2 allele was 0.90. These frequencies are slightly lower than those reported in previous studies involving populations of the same breed, but the number of animals, herein, genotyped was higher. Thus, the estimates are believed to be better and are also equally high. The Guzerat cattle has the potential for A2 milk production since most animals of the herd carry the favorable genotype for A2 milk production. Furthermore, the frequency of the A2A2 genotype can be rapidly increased by marker-assisted selection without compromising genetic variability.

Drivers of linking of Prato cheeses: An evaluation using the check all that apply (CATA) and temporal dominance of sensations (TDS) tools

Prato cheese is one of the most consumed dairy products around the word, mainly in Brazil, being the second most produced cheese in the country. However, a great variation in the cheeses sensory profiles is observed. Therefore, knowledge about the attributes that drives the product acceptance is important for Prato cheese standardization, targeting the best production conditions for obtaining cheese quality improvement. Moreover, this study also contributes with information about the TDS and CATA methodologies for the sensory field. TDS and CATA were useful tools determining liking directors of Brazilian Prato cheese. Creamy, Salt and soft attributes were indicated as drivers of liking of Prato cheese, while hard, rubbery and bitter taste contributed negatively to the acceptance of the product.

Is There a Promising Market for the A2 Milk? Analysis of Italian Consumer Preferences

Milk consumption has been on the decline for decades. Part of the cause for this is due to changes in consumer behavior and interest in healthy eating. The aim of this study was to estimate the premium price that consumers are willing to pay for A2 milk. A2 milk is a newcomer type of product containing only A2 beta-casein that is spreading in many countries of the world as a functional food. In addition, it is produced by traditional breeds of cattle that are adapted to the marginal areas and could be a virtuous model of the sustainable management system to which the consumer lately seems to turn in an increasingly conscious way. To accomplish this aim, contingent valuation has been used, which permits using a survey and a direct estimation of the premium price that consumers are willing to pay (WTP). The question format used is a dichotomous choice valuation based on a double-bound model. Statistical analysis was carried out using descriptive statistical analysis. The empirical results reveal that consumers are willing to pay a premium for A2 milk. In addition, individuals interested in product quality and already buying functional products are attracted to this type of product.