Partitioning of starter bacteria and added exogenous enzyme activities between curd and whey during Cheddar cheese manufacture

peer-reviewedPartitioning of starter bacteria and enzyme activities was investigated at different stages of Cheddar cheese manufacture using three exogenous commercial enzyme preparations added to milk or at salting. The enzyme preparations used were: Accelase AM317, Accelase AHC50, Accelerzyme CPG. Flow cytometric analysis indicated that AHC50 or AM317 consisted of permeabilised or dead cells and contained a range of enzyme activities. The CPG preparation contained only carboxypeptidase activity. Approximately 90% of starter bacteria cells partitioned with the curd at whey drainage. However, key enzyme activities partitioned with the bulk whey in the range of 22%–90%. An increased level of enzyme partitioning with the curd was observed for AHC50 which was added at salting, indicating that the mode of addition influenced partitioning. These findings suggest that further scope exists to optimise both bacterial and exogenous enzyme incorporation into cheese curd to accelerate ripening.Department of Agriculture, Food and the Marin

Enzyme Modified Cheese Flavour Ingredients

End of Project ReportEnzyme-modified cheeses (EMCs) are defined as concentrated cheese flavours produced enzymatically from cheeses of various ages and are principally used as an ingredient in processed foods, where they provide a cost-effective alternative to natural cheese. They can be used as the sole source of cheese flavour to intensify an existing cheese taste, or to impart a specific cheese character to a more bland product. Their main applications are in processed cheese, analogue cheese, cheese spreads, snack foods, soups, sauces, biscuits, dips and pet foods. Their main advantages over other cheese flavour ingredients are: low production costs, consistency, high flavour intensity, diverse flavour range, extended shelf- life, low storage costs and increased functionality. EMCs are generated utilising the same flavour pathways that occur in natural cheese ripening i.e. proteolysis, lipolysis and glycolysis. They are not as easy to differentiate as natural cheeses, as they are characterised by flavour and aroma alone as texture is not a factor in EMC production. The relationship of the flavour of EMCs to the flavour of the corresponding natural cheese remains unclear. This is especially true for Cheddar EMC which is commercially available in a range of Cheddar flavours . Despite the fact that a wide range of commercial EMCs are available, there is very little detailed information available regarding their properties or the specific production processes used. The main objective of this research was to build a knowledge base on EMC products and to utilise this to develop a biotechnological process for the production of improved enzyme modified cheeses for use as flavour ingredients. The strategy was to establish quantitative relationships between the compositional, proteolytic and lipolytic parameters and the sensory characteristics of EMCs. This data would then be used to develop a predictive model for flavour development in EMC production and the subsequent generation of an optimised EMC process enabling the generation of a range of cheese flavours from single or multiple substrates.Department of Agriculture, Food and the Marin

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

Effect of coagulant type and level on the properties of half-salt, half-fat Cheddar cheese made with or without adjunct starter: Improving texture and functionality

peer-reviewedThe potential of increasing proteolysis as a means of enhancing the texture and heat-induced flow of half-fat, half-salt Cheddar cheese made with control culture (CL, Lactococcus lactis subsp. cremoris/lactis) or adjunct culture (AC, CL + Lactobacillus helveticus) was investigated. Proteolysis was altered by substituting bovine chymosin (BC) with camel chymosin (CC), or by a 2.5-fold increase in level of BC. In cheese with CL-culture, increasing BC led to a large increase in pH and more rapid degradation of αS1-casein during maturation, and cheese that was less firm after 180 d. In contrast, substitution of BC with CC in cheeses made with CL-culture had an opposite effect. While chymosin type and level had a similar influence on αS1-casein hydrolysis in the AC-culture cheeses, it did not affect texture or flowability. Grading indicated that cheese made with AC-culture and with a higher level of BC was the most appealing

Model System for the Production of Enzyme Modified Cheese (EMC) Flavours.

End of Project ReportNatural cheese flavour ingredients, in the form of enzyme modified cheeses (EMCs), are widely used in the convenience food industry and can provide high volume added opportunities for the cheese industry. Many EMCs are produced using commercial enzyme preparations and previous studies have indicated that they contain side activities in addition to their stated main activity (see DPRC Report No.10). Therefore, it is critical that the exact enzyme complement of these preparations are known before they can be used to produce EMC of specific requirements on a consistent basis. The scientific basis of rapid enzyme mediated flavour formation in the production of EMCs is not fully understood. Consequently this knowledge gap is a major obstacle in the development of high value cheese flavour ingredients. Hence, a major objective of this project was to deepen the scientific understanding of flavour formation with a view to the production of natural enzyme-mediated dairy flavour ingredients with commercial potential. The ultimate aim was to develop the technology to produce customised high value dairy flavour ingredients in an optimised process.Dairy LevyDepartment of Agriculture, Food and the Marin

Establishment of Enabling Technology for Manufacture of Selected Types of Continental and Speciality Cheeses

End of Project ReportThe objectives in the project were the development of the science and technology for speciality cheese manufacture, identification and overcoming of the technical constraints to the manufacture of soft speciality cheeses in Ireland and the development of Moorepark Technology Limited (MTL) pilot plant as an integrated, flexible pre-commercial manufacturing platform with which to evaluate the market for speciality cheese.Department of Agriculture, Food and the Marin

Changes in fatty acid and tocopherol content during almond (Prunus dulcis, cv. Nonpareil) kernel development

Lipids are the major nutritional component of almonds and almond lipids comprise a range of fatty acids from C14 up to C20, including saturated, monounsaturated and polyunsaturated fatty acids, and oil soluble compounds such as plant sterols and tocopherols. This study investigated the change in fatty acid and tocopherol levels during almond kernel maturation, in the variety Nonpareil, grown in the Adelaide Plains of South Australia. The investigation was carried out between November 2012 and February 2013. The accumulation of lipids was determined over six timepoints, commencing at 74 days post-anthesis, and then at 20 day intervals. Almond lipid accumulation occurred rapidly between 95 and 115 days post-anthesis, i.e. at a rate of up to 1.83 g/day per 100 g fresh weight but then slowed. Tocopherols accumulated steadily and were positively correlated with lipid development; with α-tocopherol forming at the highest rate, being 0.58 mg/day in 100 g lipid, between the first two timepoints. The key timing for accumulation of the major fatty acid, oleic acid, was between 95 and 115 days post-anthesis, after which accumulation remained constant, at 0.57% of total lipids per day. In contrast, linoleic acid accumulated during the first two timepoints then declined to 23% of final lipid content. This study aimed to determine the timing of almond lipophilic antioxidant production, to inform almond orchard management practices, such as irrigation and fertilisation, which may impact kernel composition, and therefore, quality.Ying Zhu, Kerry L. Wilkinson, Michelle Wirthensoh

Quantum correction to the Kubo formula in closed mesoscopic systems

We study the energy dissipation rate in a mesoscopic system described by the parametrically-driven random-matrix Hamiltonian H[\phi(t)] for the case of linear bias \phi=vt. Evolution of the field \phi(t) causes interlevel transitions leading to energy pumping, and also smears the discrete spectrum of the Hamiltonian. For sufficiently fast perturbation this smearing exceeds the mean level spacing and the dissipation rate is given by the Kubo formula. We calculate the quantum correction to the Kubo result that reveals the original discreteness of the energy spectrum. The first correction to the system viscosity scales proportional to v^{-2/3} in the orthogonal case and vanishes in the unitary case.Comment: 4 pages, 3 eps figures, REVTeX

Can forest management based on natural disturbances maintain ecological resilience?

Given the increasingly global stresses on forests, many ecologists argue that managers must maintain ecological resilience: the capacity of ecosystems to absorb disturbances without undergoing fundamental change. In this review we ask: Can the emerging paradigm of natural-disturbance-based management (NDBM) maintain ecological resilience in managed forests? Applying resilience theory requires careful articulation of the ecosystem state under consideration, the disturbances and stresses that affect the persistence of possible alternative states, and the spatial and temporal scales of management relevance. Implementing NDBM while maintaining resilience means recognizing that (i) biodiversity is important for long-term ecosystem persistence, (ii) natural disturbances play a critical role as a generator of structural and compositional heterogeneity at multiple scales, and (iii) traditional management tends to produce forests more homogeneous than those disturbed naturally and increases the likelihood of unexpected catastrophic change by constraining variation of key environmental processes. NDBM may maintain resilience if silvicultural strategies retain the structures and processes that perpetuate desired states while reducing those that enhance resilience of undesirable states. Such strategies require an understanding of harvesting impacts on slow ecosystem processes, such as seed-bank or nutrient dynamics, which in the long term can lead to ecological surprises by altering the forest's capacity to reorganize after disturbance

Inkjet-based biopatterning of bone morphogenetic protein-2 to spatially control calvarial bone formation

The purpose of this study was to demonstrate spatial control of osteoblast differentiation in vitro and bone formation in vivo using inkjet bioprinting technology and to create three-dimensional persistent bio-ink patterns of bone morphogenetic protein-2 (BMP-2) and its modifiers immobilized within microporous scaffolds. Semicircular patterns of BMP-2 were printed within circular DermaMatrix™ human allograft scaffold constructs. The contralateral halves of the constructs were unprinted or printed with BMP-2 modifiers, including the BMP-2 inhibitor, noggin. Printed bio-ink pattern retention was validated using fluorescent or 125I-labeled bio-inks. Mouse C2C12 progenitor cells cultured on patterned constructs differentiated in a dose-dependent fashion toward an osteoblastic fate in register to BMP-2 patterns. The fidelity of spatial restriction of osteoblastic differentiation at the boundary between neighboring BMP-2 and noggin patterns improved in comparison with patterns without noggin. Acellular DermaMatrix constructs similarly patterned with BMP-2 and noggin were then implanted into a mouse calvarial defect model. Patterns of bone formation in vivo were comparable with patterned responses of osteoblastic differentiation in vitro. These results demonstrate that three-dimensional biopatterning of a growth factor and growth factor modifier within a construct can direct cell differentiation in vitro and tissue formation in vivo in register to printed patterns. © 2010 Mary Ann Liebert, Inc