Impact of dietary regime on the metabolomic profile of bovine buttermilk and whole milk powder.

INTRODUCTION: Bovine milk contains a rich matrix of nutrients such as carbohydrates, fat, protein and various vitamins and minerals, the composition of which is altered by factors including dietary regime. OBJECTIVES: The objective of this research was to investigate the impact of dietary regime on the metabolite composition of bovine whole milk powder and buttermilk. METHODS: Bovine whole milk powder and buttermilk samples were obtained from spring-calving cows, consuming one of three diets. Group 1 grazed outdoors on perennial ryegrass which was supplemented with 5% concentrates; group 2 were maintained indoors and consumed a total mixed ration diet; and group 3 consumed a partial mixed ration diet consisting of perennial ryegrass during the day and total mixed ration maintained indoors at night. RESULTS: Metabolomic analysis of the whole milk powder (N = 27) and buttermilk (N = 29) samples was preformed using liquid chromatography-tandem mass spectrometry, with 504 and 134 metabolites identified in the samples respectively. In whole milk powder samples, a total of 174 metabolites from various compound classes were significantly different across dietary regimes (FDR adjusted p-value ≤ 0.05), including triglycerides, of which 66% had their highest levels in pasture-fed samples. Triglycerides with highest levels in pasture-fed samples were predominantly polyunsaturated with high total carbon number. Regarding buttermilk samples, metabolites significantly different across dietary regimes included phospholipids, sphingomyelins and an acylcarnitine. CONCLUSION: In conclusion the results reveal a significant impact of a pasture-fed dietary regime on the metabolite composition of bovine dairy products, with a particular impact on lipid compound classes.

Multispecies pasture diet and cow breed impacts on milk composition and quality in a seasonal spring-calving dairy production system.

In recent years, there has been significant emphasis on the composition of pasture-based cow feed and the potential benefits of incorporating multispecies swards to improve sustainability and biodiversity. This study compared the effects of a conventional perennial ryegrass (PRG) monoculture supported by high chemical nitrogen (N) usage with a low chemical N application multispecies sward system (MSS) on the composition and quality of milk across lactation using spring-calving Holstein-Friesian (HF) and Jersey Holstein-Friesian (JFX) cows. Bulk milk samples (n = 144) were collected from each group at morning and evening milking on a weekly basis (n = 36) throughout lactation and analyzed for gross composition and physico-chemical properties. Cow breed had a significant impact on milk profile, with milk from HF cows having significantly smaller milk fat globule (MFG) size, higher instability index values, higher yield, and lower total solids levels, compared with JFX cows. Notably, HF cows had increased milk total solids and fat levels when fed on MSS, as opposed to the PRG-fed HF cows. Feeding MSS pasture increased creaming velocity values in mid and late lactation, and resulted in similar milk gross composition to PRG. In comparison to PRG, MSS-fed groups showed significantly increased total solids yield, including higher levels of protein and fat yield. In late lactation, MSS feeding was associated with reduced MFG size. All physicochemical properties studied (MFG size, creaming velocity, instability index) showed decreasing values from early to late lactation stage. Overall, these findings demonstrate the significant effects of cow diet, breed and stage of lactation on compositional and physico-chemical characteristics of milk, with important implications for milk processing and dairy product quality.

Pasture feeding improves the nutritional, textural, and techno-functional characteristics of butter.

There is an increasing consumer desire for pasture-derived dairy products, as outdoor pasture-based feeding systems are perceived as a natural environment for animals. Despite this, the number of grazing animals globally has declined as a result of the higher milk yields achieved by indoor TMR feeding systems, in addition to the changing climatic conditions and lower grazing knowledge and infrastructure. This has led to the development of pasture-fed standards, stipulating the necessity of pasture and its minimum requirements as the primary feed source for products advertising such claims, with various requirements depending on the region for which it was produced. This work investigates the differences in the composition and techno-functional properties of butters produced from high, medium and no pasture allowance diets during early, mid, and late lactation. Butters were produced using milks collected from 3 feeding systems: outdoor pasture grazing (high pasture allowance); indoor TMR (no pasture allowance); and a partial mixed ration (medium pasture allowance) system, which involved outdoor pasture grazing during the day and indoor TMR feeding at night. Butters were manufactured during early, mid, and late lactation. Creams derived from TMR feeding systems exhibited the highest milk fat globule size. The fatty acid profiles of butters also differed significantly as a function of diet and could be readily discriminated by partial least squares analysis. The most important fatty acids in such an analysis, as indicated by their highest variable importance projection scores, were CLA C18:2 cis-9,trans-11 (rumenic acid), C16:1n-7 trans (trans-palmitoleic acid), C18:1 trans (elaidic acid), C18:3n-3 (α-linolenic acid), and C18:2n-6 (linoleic acid). Increasing pasture allowances resulted in reduced crystallization temperatures and hardness of butters and concurrently increasing the "yellow" color. Yellow color was strongly correlated with Raman peaks commonly associated with carotenoids. The milk fat globule size of cream decreased with advancing stage of lactation and churning time of cream was lowest in early lactation. Differences in the fatty acid and triglyceride contents of butter as a result of lactation and dietary effects demonstrated significant correlations with the hardness, rheological, melting, and crystallization profiles of the butters. This work highlighted the improved nutritional profile and functional properties of butter with increasing dietary pasture allowance, primarily as a result of increasing proportions of unsaturated fatty acids. Biomarkers of pasture feeding (response in milk proportionate to the pasture allowance) associated with the pasture-fed status of butters were also identified as a result of the significant changes in the fatty acid profile with increasing pasture allowance. This was achieved through the use of 3 authentic feeding systems with varying pasture allowances, commonly operated by farmers around the world and conducted across 3 stages of lactation.

The impact of seasonal calving systems with varying pasture allowance on Cheddar cheese composition, nutritional quality and ripening characteristics.

The objective of this study was to examine the impact of stage of lactation (early, mid and late) and proportion of pasture in the cows diet (high: GRS, medium: PMR and no: TMR) on the composition and quality of Cheddar cheese. Triplicate trials were carried out in each stage of lactation, and milk protein and fat contents were standardized for Cheddar cheese manufacture at pilot scale. As cheese milks were standardized for milk fat and protein contents, gross composition did not differ as a result of diet. Fatty acid profiles of GRS cheese were significantly different from TMR, while PMR profiles were less distinct and more similar to both GRS and TMR profiles, as illustrated by partial least squares discriminatory analysis. Fatty acids including CLA C18:2 cis-9, trans-11, C22:1 n-9 and C18:3 n-3 were most influential in this separation of profiles. Fatty acid profiling revealed that GRS derived cheese contained higher proportions of nutrients considered beneficial for human health including higher proportions of unsaturated fatty acids and omega-3 fatty acids. A biomarker model utilizing the proportions of 5 fatty acids was constructed and was effective at distinguishing between cheese of GRS, TMR and PMR feeding systems. Proportions of ρ-κ-casein, αs2-casein and αs1-casein in cheese also differed between diets while proportions of ρ-κ-casein, αs1-casein and ß-casein were lowest in late lactation cheese. The impact of diet was less influential compared with that of stage of lactation on the ripening characteristics of cheese. An index of primary proteolysis was highest in late lactation cheese. The peptides derived from the proteolysis of κ-casein and ß-casein and levels of secondary proteolysis, in particular, the proportions of 12 free amino acids were most influenced by stage of lactation. Overall this study demonstrated the effects of increasing pasture allowance and stage of lactation on the nutritional quality and ripening properties of Cheddar cheese.

Impact of varying levels of pasture allowance on the nutritional quality and functionality of milk throughout lactation.

The objective of this study was to examine the impact of increasing proportions of grazed pasture in the diet on the composition, quality, and functionality of bovine milk across a full lactation. Fifty-four spring-calving cows were randomly assigned to 1 of 3 groups (n = 18), blocked on the basis of mean calving date (February 15, 2020 ± 0.8 d), pre-experimental daily milk yield (24.70 ± 3.70 kg), milk solids yield (2.30 ± 0.27 kg), lactation number (3.10 ± 0.13), and economic breeding index (182 ± 19). Raw milk samples were obtained weekly from each group between March and November 2020. Group 1 (GRS) consumed perennial ryegrass and was supplemented with 5% concentrates (dry matter basis); group 2 was maintained indoors and consumed a total mixed ration (TMR) diet consisting of maize silage, grass silage, and concentrates; and group 3 consumed a partial mixed ration diet (PMR), rotating between perennial ryegrass during the day and indoor TMR feeding at night. Raw milk samples consisted of a pooled morning and evening milking and were analyzed for gross composition, free amino acids, fatty acid composition, heat coagulation time, color, fat globule size, and pH. The TMR milks had a significantly higher total solids, lactose, protein, and whey protein as a proportion of protein content compared with both GRS and PMR milks. The GRS milks demonstrated a significantly lower somatic cell count (SCC), but a significantly higher pH and b*-value than both TMR and PMR milks. The PMR milks exhibited significantly lower total solids and fat content, but also demonstrated significantly higher SCC and total free amino acid content compared with GRS and TMR. Partial least squares discriminant analysis of fatty acid profiles displayed a distinct separation between GRS and TMR samples, while PMR displayed an overlap between both GRS and TMR groupings. Variable importance in projection analysis identified conjugated linoleic acid cis-9,trans-11, C18:2n-6 cis, C18:3n-3, C11:0, and C18:2n-6 trans as the largest contributors to the variation between the diets. Milk fats derived from GRS diets exhibited the highest proportion of unsaturated fats and higher unsaturation, health-promoting, and desaturase indices. The lowest proportions of saturated fats and the lowest atherogenic index were also exhibited by GRS-derived milk fats. This work highlights the positive influence of grass-fed milk for human consumption through its more nutritionally beneficial fatty acid profile, despite the highest milk solid percentages derived from TMR feeding systems. Furthermore, this study demonstrates the proportional response of previously highlighted biomarkers of pasture feeding to the proportion of pasture in the cow's diet.

Milk fat: opportunities, challenges and innovation.

Milk fat is a high-value milk component that is processed mainly as butter, cheese, cream and whole milk powder. It is projected that approximately 35 million tonnes of milk fat will be produced globally by 2025. This surplus, enhances the need for diversification of milk fat products and the milk pool in general. Infant milk formula producers, for instance, have incorporated enzyme modified ("humanised") milk fat and fat globule phospholipids to better mimic human milk fat structures. Minor components like mono- and di-glycerides from milk fat are increasingly utilized as emulsifiers, replacing palm esters in premium-priced food products. This review examines the chemistry of milk fat and the technologies employed for its modification, fractionation and enrichment. Emerging processing technologies such as ultrasound, high pressure processing, supercritical fluid extraction and fractionation, can be employed to improve the nutritional and functional attributes of milk fat. The potential of recent developments in biological intervention, through dietary manipulation of milk fatty acid profiles in cattle also offers significant promise. Finally, this review provides evidence to help redress the imbalance in reported associations between milk fat consumption and human health, and elucidates the health benefits associated with consumption of milk fat and dairy products.

Invited review: A 2020 perspective on pasture-based dairy systems and products.

Grazing pasture is the basis for dairy production systems in regions with temperate climates, such as in Ireland, New Zealand, parts of Australia, the United States, and Europe. Milk and dairy products from cows on pasture-based farms predominantly consuming fresh grazed grass (typically classified as "grass-fed" milk) have been previously shown to possess a different nutrient profile, with potential nutritional benefits, compared with conventional milk derived from total mixed ration. Moreover, pasture-based production systems are considered more environmentally and animal welfare friendly by consumers. As such, there is significant potential for market capitalization on grass-fed dairy products. As competition in this space increases, the regulations of what constitutes as grass-fed vary between different regions of the world. With this in mind, there is a need for clear and independently accredited grass-fed standards, defining the grass-fed criteria for labeling of products as such, subsequently increasing the clarity and confidence for the consumer. This review outlines the numerous effects of pasture production systems on dairy product composition, nutritional profile, and sustainability, and highlights potential future methods for authentication.

Compositional and functional properties of milk and dairy products derived from cows fed pasture or concentrate-based diets.

Worldwide milk production is predominantly founded on indoor, high-concentrate feeding systems, whereas pasture-based feeding systems are most common in New Zealand and Ireland but have received greater attention recently in countries utilizing conventional systems. Consumer interest in 'pasture-fed' dairy products has also increased, arising from environmental, ethical, and nutritional concerns. A substantial body of research exists describing the effect of different feeding strategies on the composition of milk, with several recent studies focusing on the comparison of pasture- and concentrate-based feeding regimes. Significant variation is typically observed in the gross composition of milk produced from different supplemental feeds, but various changes in the discrete composition of macromolecular components in milk have also been associated with dietary influence, particularly in relation to the fatty acid profile. Changes in milk composition have also been shown to have implications for milk and dairy product processability, functionality and sensory properties. Methods to determine the traceability of dairy products or verify marketing claims such as 'pasture-fed' have also been established, based on compositional variation due to diet. This review explores the effects of feed types on milk composition and quality, along with the ultimate effect of diet-induced changes on milk and dairy product functionality, with particular emphasis placed on pasture- and concentrate-based feeding systems.

Effect of Pseudomonas fluorescens proteases on the quality of Cheddar cheese.

The objective of this study was to investigate the effect of adding different levels of a thermoresistant protease produced by a Pseudomonas fluorescens strain to milk on the manufacture and quality of Cheddar cheese. Fresh raw milk was collected, standardized, and pasteurized at 72°C for 15 s, and the enzyme was added to give a protease activity of 0.15 or 0.60 U/L (treatments P1 and P4, respectively), while one sample had no enzyme added (control). Milk was stored at 4°C for 48 h and Cheddar cheese was manufactured after 0 and 48 h of storage. Results indicated that the protease was active in milk during 48 h of storage; however, its effect on milk composition was minimal. The protein that was preferentially hydrolyzed by the protease over storage was ß-casein, followed by κ-casein. The mean cheese yield and recovery of fat and protein obtained for all cheeses were not affected by protease activity. The protease showed low activity during cheese manufacture, possibly because of unfavorable conditions, including low pH. One of the factors that might have influenced protease activity was the pH of the curd (approximately 6.55 after acidification and 5.35 at milling), which was lower than that at which the enzyme would have optimum activity (pH 7 to 9). Consequently, the composition, pH, patterns of proteolysis, and hardness of all cheeses produced were similar and in accordance with values expected for that type of cheese, independently of the protease activity level. However, slight increases in proteolysis were observed in P4 cheeses and produced using milk stored for 48 h. Both the P1 and P4 cheeses had higher concentrations of free amino acids (FAA) compared with the control, whereas urea-PAGE electrophoretograms indicated a greater breakdown of caseins in the P4 cheese samples, which may be related to possible increases in numbers of proteolytic bacteria in milk during storage. Therefore, the thermoresistant psychrotrophic bacterial protease(s) tested in this study may affect the manufacture or quality of Cheddar cheese during ripening to a relatively limited extent. However, controlling initial levels of proteolytic bacteria in raw milk remains essential, because proteolysis affects the development of flavor and texture in cheese.

Physicochemical properties of whole milk powder derived from cows fed pasture or total mixed ration diets.

This study examined the effect of dietary factors on compositional and functional properties of whole milk powder (WMP) produced from bovine milk. Raw milk samples were obtained from 3 groups of 18 Holstein Friesian spring-calving cows randomly assigned to diets based on perennial ryegrass (GRS), perennial ryegrass/white clover sward (CLV), and total mixed ration (TMR). Raw milks obtained in late lactation were subsequently standardized for fat, heat-treated (90°C for 30 s), evaporated, and homogenized before spray drying. The WMP produced from each diet were analyzed to determine differences in color, particle size distribution, heat coagulation time, yogurt gelation, texture profile, and protein profile due to each diet. Significant differences in heat coagulation time were observed between the CLV and TMR samples, whereas color values were significantly different between GRS and TMR samples. No significant differences in gross composition, protein profile, or whey protein nitrogen index were found between the 3 WMP samples. Average D90 values (the particle size at which 90% of the particles were smaller than the specified size) for fat globules were significantly lower in the TMR sample compared with the GRS and CLV samples. Yogurts produced from GRS- and CLV-derived WMP had significantly higher elastic moduli (G') than those produced from TMR-derived WMP. Similarly, texture profile analysis revealed significantly higher firmness values in yogurt samples derived from CLV compared with TMR samples. Our data characterize the effect of these diets on the composition and functional properties of fat-standardized WMP, suggesting better yogurt functionality and thermal stability in WMP derived from pasture-based bovine diets.

Dietary Compounds Influencing the Sensorial, Volatile and Phytochemical Properties of Bovine Milk.

The main aim of this study was to evaluate the volatile profile, sensory perception, and phytochemical content of bovine milk produced from cows fed on three distinct feeding systems, namely grass (GRS), grass/clover (CLV), and total mixed ration (TMR). Previous studies have identified that feed type can influence the sensory perception of milk directly via the transfer of volatile aromatic compounds, or indirectly by the transfer of non-volatile substrates that act as precursors for volatile compounds. In the present study, significant differences were observed in the phytochemical profile of the different feed and milk samples. The isoflavone formonoetin was significantly higher in CLV feed samples, but higher in raw GRS milk, while other smaller isoflavones, such as daidzein, genistein, and apigenin were highly correlated to raw CLV milk. This suggests that changes in isoflavone content and concentration in milk relate to diet, but also to metabolism in the rumen. This study also found unique potential volatile biomarkers in milk (dimethyl sulfone) related to feeding systems, or significant differences in the concentration of others (toluene, p-cresol, ethyl and methyl esters) based on feeding systems. TMR milk scored significantly higher for hay-like flavor and white color, while GRS and CLV milk scored significantly higher for a creamy color. Milk samples were easily distinguishable by their volatile profile based on feeding system, storage time, and pasteurization.

Effect of different forage types on the volatile and sensory properties of bovine milk.

The effect of 3 diets (grass, grass/clover, and total mixed ration) on the volatile and sensory properties of bovine milk was assessed over an entire lactation season. Little evidence was found of direct transfer of terpenes into raw milk from the different diets, and it is likely that the monocultures of ryegrass used with and without white clover were factors as these contained very few terpenes. Evidence of direct transfer of nonterpene volatiles from forage to the subsequent raw milks was probable; however, differences in the protein carbohydrate availability and digestion in the rumen appeared to have a greater contribution to volatile profiles. Pasteurization significantly altered the volatile profiles of all milks. A direct link between the milk fatty acid content, forage, and volatile products of lipid oxidation was also evident and differences in fatty acid content of milk due to forage may also have influenced the viscosity perception of milk. Irish sensory assessors preferred pasteurized milk produced from grass-fed cows, with least preference from milk produced from total mixed ration diets. ß-Carotene content was significantly higher in milks derived from grass or grass/clover and appears to have directly influenced color perception. Toluene and p-cresol are both degradation products of ß-carotene and along with ß-carotene were identified as potential biomarkers for milk derived from pasture. The only correlation that appeared to influence the flavor of milk as determined using ranked descriptive analysis was p-cresol. P-Cresol appears to be responsible for the barnyard aroma of milk and is also likely derived from the deamination and decarboxylation of tryptophan and tyrosine due to the higher levels of available protein in the grass and grass/clover diets. The highest levels of p-cresol were in the grass/clover diets and are likely due to the degradation of the isoflavone formononetin in the rumen, which is present in white clover swards.

Chlorate and Other Oxychlorine Contaminants Within the Dairy Supply Chain.

The presence of chlorate in milk and dairy products can arise from the use of chlorinated water and chlorinated detergents for cleaning and sanitation of process equipment at both farm and food processor level. Chlorate and other oxychlorine species have been associated with inhibition of iodine uptake in humans and the formation of methemoglobin, with infants and young children being a high-risk demographic. This comprehensive review of chlorate and chlorine derivatives in dairy, highlights areas of concern relative to the origin and/or introduction of chlorate within the dairy supply chain. This review also discusses the associated health concerns, regulations, and chemical behavior of chlorate and chlorine-derived by-products, and provides a summary of mechanisms for their detection and removal.

Effect of pasture versus indoor feeding systems on quality characteristics, nutritional composition, and sensory and volatile properties of full-fat Cheddar cheese.

The purpose of this study was to investigate the effects of pasture-based versus indoor total mixed ration (TMR) feeding systems on the chemical composition, quality characteristics, and sensory properties of full-fat Cheddar cheeses. Fifty-four multiparous and primiparous Friesian cows were divided into 3 groups (n = 18) for an entire lactation. Group 1 was housed indoors and fed a TMR diet of grass silage, maize silage, and concentrates; group 2 was maintained outdoors on perennial ryegrass only pasture (GRS); and group 3 was maintained outdoors on perennial ryegrass/white clover pasture (CLV). Full-fat Cheddar cheeses were manufactured in triplicate at pilot scale from each feeding system in September 2015 and were examined over a 270-d ripening period at 8°C. Pasture-derived feeding systems were shown to produce Cheddar cheeses yellower in color than that of TMR, which was positively correlated with increased cheese ß-carotene content. Feeding system had a significant effect on the fatty acid composition of the cheeses. The nutritional composition of Cheddar cheese was improved through pasture-based feeding systems, with significantly lower thrombogenicity index scores and a greater than 2-fold increase in the concentration of vaccenic acid and the bioactive conjugated linoleic acid C18:2 cis-9,trans-11, whereas TMR-derived cheeses had significantly higher palmitic acid content. Fatty acid profiling of cheeses coupled with multivariate analysis showed clear separation of Cheddar cheeses derived from pasture-based diets (GRS or CLV) from that of a TMR system. Such alterations in the fatty acid profile resulted in pasture-derived cheeses having reduced hardness scores at room temperature. Feeding system and ripening time had a significant effect on the volatile profile of the Cheddar cheeses. Pasture-derived Cheddar cheeses had significantly higher concentrations of the hydrocarbon toluene, whereas TMR-derived cheese had significantly higher concentration of 2,3-butanediol. Ripening period resulted in significant alterations to cheese volatile profiles, with increases in acid-, alcohol-, aldehyde-, ester-, and terpene-based volatile compounds. This study has demonstrated the benefits of pasture-derived feeding systems for production of Cheddar cheeses with enhanced nutritional and rheological quality compared with a TMR feeding system.

Effect of pasture versus indoor feeding systems on raw milk composition and quality over an entire lactation.

The aim of this study was to investigate the effects of different feeding systems on milk quality and composition. Fifty-four multiparous and primiparous Friesian lactating cows were divided into 3 groups (n=18) to study the effects of 3 feeding systems over a full lactation. Group 1 was housed indoors and offered a total mixed ration diet (TMR), group 2 was maintained outdoors on a perennial ryegrass pasture (referred to as grass), and group 3 was also grazed outdoors on a perennial ryegrass/white clover pasture (referred to as clover). Bulk milk samples were collected from each group at morning and afternoon milkings once weekly from March 11 to October 28 in 2015. Milk from pasture-fed cows (grass and clover) had significantly higher concentrations of fat, protein, true protein, and casein. The pasture feeding systems induced significantly higher concentrations of saturated fatty acids C11:0, C13:0, C15:0, C17:0, C23:0, and unsaturated fatty acids C18:2n-6 trans, C18:3n-3, C20:1, and C20:4n-6 and a greater than 2-fold increase in the conjugated linoleic acid C18:2 cis-9,trans-11 content of milk compared with that of the TMR feeding system. The TMR feeding system resulted in milks with increased concentrations of C16:0, C18:2n-6 cis, C18:3n-6 cis, C22:0 C22:1n-9, and C18:2 cis-10,trans-12. Principal component analysis of average fatty acid profiles showed clear separation of milks from the grazed pasture-based diets to that of a TMR system throughout lactation, offering further insight into the ability to verify pasture-derived milk by fatty acid profiling.

Quality characteristics, chemical composition, and sensory properties of butter from cows on pasture versus indoor feeding systems.

This study evaluated the effects of 3 widely practiced cow feeding systems in the United States, Europe, and Southern Hemisphere regions on the characteristics, quality, and consumer perception of sweet cream butter. Fifty-four multiparous and primiparous Friesian cows were divided into 3 groups (n=18) for an entire lactation. Group 1 was housed indoors and fed a total mixed ration diet (TMR) of grass silage, maize silage, and concentrates; group 2 was maintained outdoors on perennial ryegrass-only pasture (GRS); and group 3 was maintained outdoors on a perennial ryegrass/white clover pasture (CLV). Mid-lactation butter was manufactured in triplicate with milk from each group in June 2015 (137±7d in milk) and was analyzed over a 6-mo storage period at 5°C for textural and thermal properties, fatty acid composition, sensory properties, and volatile compounds. The nutritional value of butters was improved by pasture feeding, and butter from pasture-fed cows had significantly lower thrombogenicity index scores compared with butters from TMR-fed cows. In line with these results, pasture-derived milks (GRS and CLV) produced butter with significantly higher concentrations of conjugated linoleic acid (cis-9,trans-11) and trans-ß-carotene than TMR butter. Alterations in the fatty acid composition of butter contributed to significant differences in textural and thermal properties of the butters. Total mixed ration-derived butters had significantly higher hardness scores at room temperature than those of GRS and CLV. Onset of crystallization for TMR butters also occurred at significantly higher temperatures compared with pasture butters. Volatile analysis of butter by gas chromatography-mass spectrometry identified 25 compounds present in each of the butters, 5 of which differed significantly based on feeding system, including acetone, 2-butanone, 1-pentenol, toluene, and ß-pinene. Toluene was very significantly correlated with pasture-derived butter. Sensory analysis revealed significantly higher scores for GRS-derived butter in several attributes including "liking" of appearance, flavor, and color over those of TMR butter. Partial least square regression plots of fatty acid profiles showed clear separation of butter derived from grazed pasture-based perennial ryegrass or perennial rye/white clover diets from that of a TMR system, offering further insight into the ability of fatty acid profiling to verify such pasture-derived dairy products.

Impact of feeding regimes and lactation stage on sensory attributes of Cheddar cheese.

This study investigated the effects of diet and stage of lactation (SOL) on sensory profiles, texture, volatile profiles, and colour of Cheddar cheese. Cheddar cheese was manufactured from early-, mid-, and late-lactation milk obtained from seasonally calved cows (n = 54). Cows were assigned a diet; group 1: perennial ryegrass (GRS), group 2: total mixed ration (TMR), and group 3: partial mixed ration (PMR). Instrumental analysis was performed at 270 days (mature Cheddar). Sensory evaluation took place after 548 days (extra mature Cheddar). Toluene was the only volatile compound that was significantly influenced by diet. The trained panel rated early-lactation cheese as stronger than mid- and late- for cowy/barny flavour and late-lactation cheese as sweeter than early- and mid-lactation cheese. Mid-lactation cheese was liked least overall. Early-lactation cheeses were rated higher for 'crumbly' texture than mid- and late. Diet affected consumer ratings, with GRS and PMR cheese rated as more intense than TMR for flavour, aftertaste, and saltiness. Consumers reported that TMR cheese was lighter in colour compared to GRS cheese, which was supported by instrumental analysis. Consumers perceived GRS as more springy and less crumbly than TMR and PMR, while Texture Profile Analysis indicated that TMR was harder than GRS. Consumer segmentation was observed with two clear preference groups, one preferring GRS and one preferring TMR. For both groups, 'taste' seemed to be the main driver of liking, highlighting that consumer preference is most impacted by individual taste preferences.

The detailed analysis of the microbiome and resistome of artisanal blue-veined cheeses provides evidence on sources and patterns of succession linked with quality and safety traits.

BACKGROUND: Artisanal cheeses usually contain a highly diverse microbial community which can significantly impact their quality and safety. Here, we describe a detailed longitudinal study assessing the impact of ripening in three natural caves on the microbiome and resistome succession across three different producers of Cabrales blue-veined cheese. RESULTS: Both the producer and cave in which cheeses were ripened significantly influenced the cheese microbiome. Lactococcus and the former Lactobacillus genus, among other taxa, showed high abundance in cheeses at initial stages of ripening, either coming from the raw material, starter culture used, and/or the environment of processing plants. Along cheese ripening in caves, these taxa were displaced by other bacteria, such as Tetragenococcus, Corynebacterium, Brevibacterium, Yaniella, and Staphylococcus, predominantly originating from cave environments (mainly food contact surfaces), as demonstrated by source-tracking analysis, strain analysis at read level, and the characterization of 613 metagenome-assembled genomes. The high abundance of Tetragenococcus koreensis and Tetragenococcus halophilus detected in cheese has not been found previously in cheese metagenomes. Furthermore, Tetragenococcus showed a high level of horizontal gene transfer with other members of the cheese microbiome, mainly with Lactococcus and Staphylococcus, involving genes related to carbohydrate metabolism functions. The resistome analysis revealed that raw milk and the associated processing environments are a rich reservoir of antimicrobial resistance determinants, mainly associated with resistance to aminoglycosides, tetracyclines, and ß-lactam antibiotics and harbored by aerobic gram-negative bacteria of high relevance from a safety point of view, such as Escherichia coli, Salmonella enterica, Acinetobacter, and Klebsiella pneumoniae, and that the displacement of most raw milk-associated taxa by cave-associated taxa during ripening gave rise to a significant decrease in the load of ARGs and, therefore, to a safer end product. CONCLUSION: Overall, the cave environments represented an important source of non-starter microorganisms which may play a relevant role in the quality and safety of the end products. Among them, we have identified novel taxa and taxa not previously regarded as being dominant components of the cheese microbiome (Tetragenococcus spp.), providing very valuable information for the authentication of this protected designation of origin artisanal cheese. Video Abstract.