Stephen Haines

Effect of Cooking on Meat Proteins: Mapping Hydrothermal Protein Modification as a Potential Indicator of Bioavailability

Thermal treatment of meat proteins induces a range of observable and molecular-level changes. In order to understand and track these heat-induced modifications at the amino acid level, various analytical techniques were used. Changes were observed both in the soluble and in the insoluble fractions after hydrothermal treatment of minced beef samples. Redox proteomics clearly indicated increasing oxidative modification of proteins with increased heat exposure. Collagens in the soluble fraction and myosin in the insoluble fraction were found to be highly susceptible to such modifications. Maillard reaction products in the insoluble and pyrrolidone formation in the soluble fraction steadily increased with increased heat exposure. Fluorescence studies indicated a rapid increase in fluorescence with heat, suggesting the formation of advanced glycation end products. Overall these results provide a deeper understanding of the effect of cooking on meat proteins and the possible relationship to processing conditions in meat-derived food.

Proteomic tracking of hydrothermal Maillard and redox modification in lactoferrin and β-lactoglobulin: Location of lactosylation, carboxymethylation, and oxidation sites

Lactoferrin and β-lactoglobulin are important protein components of mammalian milk. Maillard reactions, as well as redox chemistry, are of particular interest for dairy products because they are known to occur during common processing steps, notably heating procedures such as pasteurization. Using a redox proteomics approach, we characterized AA residue side-chain modification across a range of heating times and with or without the specific addition of lactose, to both map the key modification sites within these proteins and evaluate their sensitivity to process-induced modification. Heating in the presence of lactose resulted in significant Maillard modification (both lactosylation and carboxymethylation) to both bovine lactoferrin and β-lactoglobulin. Notably, Lys47, a key residue in the bioactive peptide lactoferricin, was particularly susceptible to modification. Lactoferrin appeared to be fairly robust to hydrothermal treatment, with relatively low levels of oxidative modification observed. In contrast, β-lactoglobulin was susceptible to significant oxidative modification under hydrothermal treatment, with the range and type of modifications observed suggesting compromised nutritional value. These results have important implications for processing applications in dairy foods where retention of biological function and optimal protein quality is desired.

Proteomic and peptidomic differences and similarities between four muscle types from New Zealand raised Angus steers

Four muscles from New Zealand-raised Angus steers were evaluated (musculus semitendinosus, m. longissimus thoracis et lumborum, m. psoas major and m. infraspinatus) to test their differences and common features in protein and peptide abundances. The ultimate goal of such a comparison is to match muscle types to products with targeted properties. Protein profiling based on two-dimensional electrophoresis showed that the overall profiles were similar, but, between muscle types, significant (p<0.05) intensity differences were observed in twenty four protein spots. Profiling of endogenous peptides allowed characterisation of 346 peptides. Quantitative analysis showed a clear distinction between the muscle types. Forty-four peptides were identified that showed a statistically significant (p<0.05) and substantial (>2-fold change) difference between at least two muscle types. These analyses demonstrate substantial similarities between these four muscle types, but also clear distinctions in their profiles; specifically a 25% difference between at least two muscles at the peptidomic level, and a 14% difference at the proteomic level.

Antler development was inhibited or stimulated by cryosurgery to periosteum or skin in a central antlerogenic region respectively.

Antler development is triggered by interactions between antler stem cells resident in the antlerogenic periosteum (AP) and the niche cells in the upper portion of overlying skin mediated by diffusible molecules. These interactive cell populations are interposed by the lower portion of the skin and the subcutaneous loose connective tissue (SLCT). It is known that mechanical deletion of just the central AP (having an area equivalent to the size of a pedicle base) by cutting through the skin and SLCT effectively stimulates the marginal AP to initiate antler development. This study was designed to investigate whether the SLCT layer plays a role in antler development by acting as a physical barrier. The results showed that the marginal AP failed to give rise to an antler after the central AP was cryosurgically destroyed with the preservation of the collagen structure of the SLCT. Furthermore, antler development was significantly advanced when the collagen structures of the skin and SLCT layers were substantially attenuated by repeated sprays with liquid nitrogen while keeping the central AP intact. Therefore, we conclude that the interposing SLCT layer acts as a physical barrier between antler stem cells and the niche cell types, and that timing of antler development is primarily controlled by the permeability of the SLCT layer to the putative interactive diffusible molecules.

Stem cells responsible for deer antler regeneration are unable to recapitulate the process of first antler development - revealed through intradermal and subcutaneous tissue transplantation.

Antlers offer a unique model for the study of whether regeneration recapitulates development in a mammalian organ. Research, to date, supports the full recapitulation in antler, but a recent report that subcutaneously transplanted (ST) pedicle periosteum (PP) failed to induce that ectopic antler formation could argue against recapitulation, as antlerogenic periosteum (AP) can readily do so. However, it was not clear in that study whether the result was caused by inability of the PP to interact with the skin or owing to failure to create the required close contact to it. This study was designed to clarify this uncertainty by adopting intradermal transplantation (IT) to achieve the required close contact without the need for significant mass expansion. The results showed that IT of 1/8 of the original AP mass or more was sufficient for antler induction, whereas ST of 1/4-AP or less could not do so within 2 years. The minimum amount of AP required for antler induction using the IT approach was somewhere between 1/8 and 1/12-AP (<30 mg). The results further demonstrated that IT of 62-84 mg PP failed to induce ectopic antler formation, even if the PP had fused with the surrounding skin. Because this mass of PP was 2-3 times the minimum amount of AP required for antler induction, we conclude that PP does not recapitulate AP in induction of ectopic antler development. It is likely that PP has been restricted for antler regeneration and lost the potential to initiate antler development.

Redox proteomic evaluation of oxidative modification and recovery in a 3D reconstituted human skin tissue model exposed to UVB.

Exposure to UV in humans resulting in sunburn triggers a complex series of events that are a mix of immediate and delayed damage mediation and healing. While studies on the effects of UV exposure on DNA damage and repair have been reported, changes in the oxidative modification of skin proteins are poorly understood at the molecular level, despite the important role played by structural proteins in skin tissue, and the effect of the integrity of these proteins on skin appearance and health. Proteomic molecular mapping of oxidation was here applied to try to enhance understanding of skin damage and recovery from oxidative damage and UVB exposure.

Feather meal-based thermoplastics: Methyl vinyl ether/maleic anhydride copolymer improves material properties

The poultry meat processing industry produces large amounts of feather meal, which is traditionally used as lowvalue plant fertilizer or fish nutrient. A higher value application for feather meal is described in this paper - a thermal blending and compression molding method to create compostable composites out of environmentally friendly materials: feather meal, glycerol, and a biodegradable copolymer of methyl vinyl ether and maleic anhydride (MVEMA). The composite’s mechanical, microstructural and chemical characteristics are described. Feather meal plasticized only with glycerol is mechanically fragile, with average tensile strength of 1.7 MPa, Young’s modulus of 296 MPa and strain-at-failure of 0.6 %. With the addition of MVEMA copolymer, feather meal is transformed into a ductile plastic composite, with tensile modulus reduced 2- to 5-fold and strain-at-failure increased 4- to 25-fold. These properties are ideal for creating feather mealbased compostable bioplastics for agricultural and industrial applications.

A mass spectrometric scoring system for oxidative damage in dairy foods

Redox proteomics is an essential component of the molecular-level characterisation of food because it can provide strong evidence for protein damage resulting from processing during the preparation stage as well as the effects of packaging post-processing up to and including retail display. Since nearly all food product quality parameters correlate directly or indirectly with protein quality and function, molecular-level characterisation of protein modification and damage is of crucial importance for the food industry. For this reason it was felt that obtaining an understanding of protein damage at the amino acid residue level and correlating it with processing parameters would ultimately lead to improvements in the processing and mitigation/repair of protein damage. To this end a damage scoring system that had been developed for the characterisation of UVB-induced photo-oxidation in wool (Dyer et al.) was modified and refined. This refinement allowed for a more advanced evaluation of redox and non-redox protein modifications, with precise weighting and thresholding functionality using LC-MS/MS data, ensuring representative coverage across all key proteins in a sample.