Effect of Milk Composition on the Quality of Fresh Fermented Dairy Products

End of Project ReportThe rheology of yogurts or fresh fermented products generally describes and measures the texture of the product and includes such terms as viscosity and firmness of the gel while syneresis refers to the tendency of the yogurt to whey-off during storage. The importance of rheology and susceptibility to syneresis of fermented milk products is that they both have major impacts on consumer perceptions of the final product quality. Indeed, variation in the quality of yogurt products can lead the consumer to experience either an over-thin watery or an over-thick stodgy texture or a product which has a high level of free whey. It is obvious that the seasonal milk supply in Ireland compounds the particular difficulties associated with achieving a consistency in the quality of yogurts or other fresh fermented products. Importantly, both the rheology and syneresis of yogurts are markedly influenced by milk composition, processing treatments and the addition of hydrocolloids. Therefore, this project was undertaken so as to develop a laboratory fermented milks model system which allows the evaluation of the effects of variation of milk components, individually or in combination, on the rheological and syneretic properties of fermented milk products such as yogurt. In particular, the effects of varying total protein, casein-to-whey protein ratio, and fat content were studied as these variations reflect both the differences in milk composition due to lactational/seasonal effects and those due to process variations such as milk heat treatment.Department of Agriculture, Food and the Marin

The Prevalence and Control of Bacillus and Related Spore-Forming Bacteria in the Dairy Industry

peer-reviewedMilk produced in udder cells is sterile but due to its high nutrient content, it can be a good growth substrate for contaminating bacteria. The quality of milk is monitored via somatic cell counts and total bacterial counts, with prescribed regulatory limits to ensure quality and safety. Bacterial contaminants can cause disease, or spoilage of milk and its secondary products. Aerobic spore-forming bacteria, such as those from the genera Sporosarcina, Paenisporosarcina, Brevibacillus, Paenibacillus, Geobacillus and Bacillus, are a particular concern in this regard as they are able to survive industrial pasteurization and form biofilms within pipes and stainless steel equipment. These single or multiple-species biofilms become a reservoir of spoilage microorganisms and a cycle of contamination can be initiated. Indeed, previous studies have highlighted that these microorganisms are highly prevalent in dead ends, corners, cracks, crevices, gaskets, valves and the joints of stainless steel equipment used in the dairy manufacturing plants. Hence, adequate monitoring and control measures are essential to prevent spoilage and ensure consumer safety. Common controlling approaches include specific cleaning-in-place processes, chemical and biological biocides and other novel methods. In this review, we highlight the problems caused by these microorganisms, and discuss issues relating to their prevalence, monitoring thereof and control with respect to the dairy industry.NG is funded by the Teagasc Walsh Fellowship Scheme and through the Irish Dairy Levy funded project ‘Thermodur-Out.

Improving the Quality of Low Fat Cheddar Cheese

End of Project ReportThe aims of this study were to elucidate the contribution of fat to cheese biochemistry and texture and to improve the texture and flavour of half-fat Cheddar cheese by modifications in make procedure, the addition of a fat mimetic, and/or the use of novel starter cultures/bacterial culture adjuncts. The main conclusions were as follows: A 'Moorepark Process' has been established for the production of half-fat Cheddar cheese with improved sensory acceptability. The flavour and texture of half-fat (17% w/w) Cheddar was improved by modification of the cheesemaking procedure and/or ripening conditions and through the use of novel starter cultures and/or bacterial culture adjuncts. Extensive databases have been compiled on: the effects of fat on the compositional, microbiological, biochemical, rheological and sensory properties of, and the yield of, Cheddar cheese. the compositional, biochemical and sensory characteristics of commercial Cheddar cheeses of different fat levels, available on the Irish and UK markets. Reduction in the fat level of Cheddar cheese resulted in a marked deterioration both in texture and flavour due to: increases in cheese hardness and fracture stress, indicating that the cheese became more elastic, tough and less amenable to mastication. a higher ratio of secondary-to-primary proteolysis a reduction in the level of primary proteolysis and an increase in the concentration of hydrophobic peptides which are conducive to bitterness.Department of Agriculture, Food and the Marin

The effect of high velocity steam injection on the colloidal stability of concentrated emulsions for the manufacture of infant formulations

peer-reviewedA major challenge for the infant formula industry is to develop more energy efficient processes while maintaining product quality and robust manufacturing practices. An effective way of improving energy utilisation is to reduce the number of processing steps during manufacture. This study examines a novel high solids process with reduced processing steps paying particular attention to emulsion stability. Model infant formulations (whey to casein ratio, 60:40) were homogenised at a solids content of 60% w/w using an in-line colloid-mill type mixer, yielding a stable emulsion with a fat globule size distribution (D(v,0.9)) of 2.99 colonm. These formulations were heat-treated using a high velocity direct steam injection device, whereby steam is accelerated using a De Laval nozzle before injection. The steam condenses on contact with the formulation, giving up latent heat, thus heating the mix. The process was found to increase the colloidal stability of the formulations, as measured in an analytical centrifuge. The fat globule size distribution was significantly (p < 0.05) decreased to 2.69 μm after processing by the injector with a concomitant significant (p < 0.05) increase in emulsion viscosity. In conclusion, in-line homogenisation followed by high velocity steam injection, using a De Laval geometry, was successfully used for heat treatment of a high solids infant formulation

Potential applications for virtual and augmented reality technologies in sensory science

peer-reviewedSensory science has advanced significantly in the past decade and is quickly evolving to become a key tool for predicting food product success in the marketplace. Increasingly, sensory data techniques are moving towards more dynamic aspects of sensory perception, taking account of the various stages of user-product interactions. Recent technological advancements in virtual reality and augmented reality have unlocked the potential for new immersive and interactive systems which could be applied as powerful tools for capturing and deciphering the complexities of human sensory perception. This paper reviews recent advancements in virtual and augmented reality technologies and identifies and explores their potential application within the field of sensory science. The paper also considers the possible benefits for the food industry as well as key challenges posed for widespread adoption. The findings indicate that these technologies have the potential to alter the research landscape in sensory science by facilitating promising innovations in five principal areas: consumption context, biometrics, food structure and texture, sensory marketing and augmenting sensory perception. Although the advent of augmented and virtual reality in sensory science offers new exciting developments, the exploitation of these technologies is in its infancy and future research will understand how they can be fully integrated with food and human responses. Industrial relevance: The need for sensory evaluation within the food industry is becoming increasingly complex as companies continuously compete for consumer product acceptance in today's highly innovative and global food environment. Recent technological developments in virtual and augmented reality offer the food industry new opportunities for generating more reliable insights into consumer sensory perceptions of food and beverages, contributing to the design and development of new products with optimised consumer benefits. These technologies also hold significant potential for improving the predictive validity of newly launched products within the marketplace

Stabilising effect of α-lactalbumin on concentrated infant milk formula emulsions heat treated pre- or post-homogenisation

peer-reviewedProtein type and/or heat treatment pre- or post-homogenisation can affect the physical stability of infant formulations during manufacture. Previous research has described the use of α-lactalbumin addition in infant formulae, but has not demonstrated the effect of heating pre- or post-emulsion formulation during processing. The objective of this study was to evaluate the effect of both of these parameters. Three batches of model 1st-stage infant formula containing differing whey protein ratios (60:40 whey: casein with α-lactalbumin content 12, 30 or 48% of total protein) were prepared. Each batch was split; one half receiving heat treatment pre-homogenisation and the second half homogenised and then heat treated. Emulsion stability was determined by size exclusion chromatography, SDS-PAGE, particle size and viscosity measurements. There was a significant (P < 0.05) reduction in the formation of large soluble aggregates upon increasing α-lac concentration in emulsions heat treated either before or after homogenisation. Heat treatment of formulations post-homogenisation resulted in a higher (P < 0.05) D.v09 within the particle size distribution; increasing α-lactalbumin concentration to 30 or 48% significantly (P < 0.05) reduced the D.v09 within the particle size distribution in these emulsions. The viscosity of concentrates (55 % total solids) containing the 12% α-lactalbumin, heat treated post-homogenisation, was significantly greater (P < 0.05) than the equivalent emulsion heat treated pre-homogenisation; increasing the α-lactalbumin concentration to 30 or 48% significantly (P < 0.05) reduced viscosity. When the α-lactalbumin content was increased to 48% as a percentage of the total protein, heating before or after emulsion formation had no effect on concentrate viscosity. The findings demonstrate the importance of thermal denaturation/aggregation of whey proteins (and in particular, the ratio of α-lactalbumin to β-lactoglobulin) prior to homogenisation of infant formula emulsions

Future Protein Supply and Demand: Strategies and Factors Influencing a Sustainable Equilibrium

peer-reviewedA growing global population, combined with factors such as changing socio-demographics, will place increased pressure on the world’s resources to provide not only more but also different types of food. Increased demand for animal-based protein in particular is expected to have a negative environmental impact, generating greenhouse gas emissions, requiring more water and more land. Addressing this “perfect storm” will necessitate more sustainable production of existing sources of protein as well as alternative sources for direct human consumption. This paper outlines some potential demand scenarios and provides an overview of selected existing and novel protein sources in terms of their potential to sustainably deliver protein for the future, considering drivers and challenges relating to nutritional, environmental, and technological and market/consumer domains. It concludes that different factors influence the potential of existing and novel sources. Existing protein sources are primarily hindered by their negative environmental impacts with some concerns around health. However, they offer social and economic benefits, and have a high level of consumer acceptance. Furthermore, recent research emphasizes the role of livestock as part of the solution to greenhouse gas emissions, and indicates that animal-based protein has an important role as part of a sustainable diet and as a contributor to food security. Novel proteins require the development of new value chains, and attention to issues such as production costs, food safety, scalability and consumer acceptance. Furthermore, positive environmental impacts cannot be assumed with novel protein sources and care must be taken to ensure that comparisons between novel and existing protein sources are valid. Greater alignment of political forces, and the involvement of wider stakeholders in a governance role, as well as development/commercialization role, is required to address both sources of protein and ensure food security.This work forms part of the ReValueProtein Research Project (Exploration of Irish Meat Processing Streams for Recovery of High Value Protein Based Ingredients for Food and Non-food Uses, Grant Award No. 11/F/043) supported by the Department of Agriculture, Food and the Marine (DAFM) under the National Development Plan 2007–2013 funded by the Irish Governmen

Mesophilic sporeformers identified in whey powder by using shotgun metagenomic sequencing

peer-reviewedSpoilage and pathogenic spore-forming bacteria are a major cause of concern for producers of dairy products. Traditional agar-based detection methods employed by the dairy industry have limitations with respect to their sensitivity and specificity. The aim of this study was to identify low-abundance sporeformers in samples of a powdered dairy product, whey powder, produced monthly over 1 year, using novel culture-independent shotgun metagenomics-based approaches. Although mesophilic sporeformers were the main target of this study, in one instance thermophilic sporeformers were also targeted using this culture-independent approach. For comparative purposes, mesophilic and thermophilic sporeformers were also tested for within the same sample using culture-based approaches. Ultimately, the approaches taken highlighted differences in the taxa identified due to treatment and isolation methods. Despite this, low levels of transient, mesophilic, and in some cases potentially pathogenic sporeformers were consistently detected in powder samples. Although the specific sporeformers changed from one month to the next, it was apparent that 3 groups of mesophilic sporeformers, namely, Bacillus cereus, Bacillus licheniformis/Bacillus paralicheniformis, and a third, more heterogeneous group containing Brevibacillus brevis, dominated across the 12 samples. Total thermophilic sporeformer taxonomy was considerably different from mesophilic taxonomy, as well as from the culturable thermophilic taxonomy, in the one sample analyzed by all four approaches. Ultimately, through the application of shotgun metagenomic sequencing to dairy powders, the potential for this technology to facilitate the detection of undesirable bacteria present in these food ingredients is highlighted

Tracking the Dairy Microbiota from Farm Bulk Tank to Skimmed Milk Powder.

peer-reviewedMicroorganisms from the environment can enter the dairy supply chain at multiple stages, including production, milk collection, and processing, with potential implications for quality and safety. The ability to track these microorganisms can be greatly enhanced by the use of high-throughput DNA sequencing (HTS). Here HTS, both 16S rRNA gene amplicon and shotgun metagenomic sequencing were applied to investigate the microbiomes of fresh mid- and late-lactation milk collected from farm bulk tanks, collection tankers, milk silos, skimmed milk silos, a cream silo, and powder samples to investigate the microbial changes throughout a skim milk powder manufacturing process. 16S rRNA gene analysis established that the microbiota of raw milks from farm bulk tanks and in collection tankers were very diverse but that psychrotrophic genera associated with spoilage, Pseudomonas and Acinetobacter, were present in all samples. Upon storage within the whole-milk silo at the processing facility, the species Pseudomonas fluorescens and Acinetobacter baumannii became dominant. The skimmed milk powder generated during the mid-lactation period had a microbial composition that was very different from that of raw milk; specifically, two thermophilic genera, Thermus and Geobacillus, were enriched. In contrast, the microbiota of skimmed milk powder generated from late-lactation milk more closely resembled that of the raw milk and was dominated by spoilage-associated psychrotrophic bacteria. This study demonstrates that the dairy microbiota can differ significantly across different sampling days. More specifically, HTS can be used to trace microbial species from raw milks through processing to final powdered products.IMPORTANCE Microorganisms can enter and persist in dairy at several stages of the processing chain. Detection of microorganisms within dairy food processing is currently a time-consuming and often inaccurate process. This study provides evidence that high-throughput sequencing can be used as an effective tool to accurately identify microorganisms along the processing chain. In addition, it demonstrates that the populations of microbes change from raw milk to the end product. Routine implementation of high-throughput sequencing would elucidate the factors that influence population dynamics. This will enable a manufacturer to adopt control measures specific to each stage of processing and respond in an effective manner, which would ultimately lead to increased food safety and quality

Pilot-scale ceramic membrane filtration of skim milk for the production of a 'humanised' protein base ingredient for infant milk formula

The protein composition of bovine skim milk was modified using pilot scale membrane filtration to produce a whey protein-dominant ingredient with a casein profile closer to human milk. Bovine skim milk was processed at low (8.9 °C) or high (50 °C) temperature using ceramic microfiltration (MF) membranes (0.1 μm mean pore diameter). The resulting permeate stream was concentrated using polyethersulfone ultrafiltration (UF) membranes (10 kDa cut-off). The protein profile of MF and UF retentate streams were determined using reversed phase-high performance liquid chromatography and polyacrylamide gel electrophoresis. Permeate from the cold MF process (8.9 °C) had a casein:whey protein ratio of ∼35:65 with no αS- or κ-casein present, compared with a casein:whey protein ratio of ∼10:90 at 50 °C. This study has demonstrated the application of cold membrane filtration (8.9 °C) at pilot scale to produce a dairy ingredient with a protein profile closer to that of human milk