title: Identifying causes of high pH in lamb meat

authors: Hontiveros, Garrianne Fatima

subjects: meat

abstract: Lamb meat export is a multi-billion-dollar New Zealand industry. Therefore, strategies to maintain and improve quality have immediate commercial benefit. Consumers judge quality by colour, tenderness, and flavour, all of which are affected by ultimate pH (pHu). Ideal meat pHu is 5.5 and is influenced by muscle glycogen concentration. Insufficient muscle glycogen at slaughter results in high pHu (>5.8) which results in tough meat, dark colour, and shorter storage life. The decrease in meat pH post-slaughter is caused by the build-up of H+ ions as a consequence of anaerobic glycolysis of glycogen for ATP formation. Physical stress depletes muscle glycogen, prompting consumers to conclude animal mistreatment. However, stress, does not necessarily equate to abuse as all animals experience some level of pre-slaughter stress and any negative effects depend on duration, type, intensity, and susceptibility. Studies have focused on post-farm-gate stressors (e.g. transport and lairage) but less clear is the role of on-farm stressors on the incidence of high pHu. The aim of this study was to investigate the variation of muscle glycogen of lambs on-farm, examine the use of heat shock protein 20 (HSP20) as a marker for physiological stress, and determine any relationship between residual glycogen level and meat quality attributes such as water binding capacity (WBC), drip loss, microbial abundance, fat, protein, and water content.  

Two observations were conducted. Firstly, 60 animals from 2 farms with different production systems: wethers (castrated males) were raised with ewes in Farm 1, whereas, intact rams, wethers, cryptorchids, and ewes were all together and introduced at different times to the group in Farm 2.  These animals were biopsied two months before slaughter, a month before, and post-rigor. On-farm, large inter-individual variation in muscle glycogen was observed in both farms but no significant difference in true glycogen between farms. Muscle glycogen levels seemed to fluctuate from one biopsy to another, contrary to previous belief that it remains constant throughout. There was no significant difference in HSP20 between farms and no correlation between muscle glycogen and HSP20 was observed. Post-rigor, 66% of carcasses from Farm 2 had high pHu (≥5.8), compared to none from Farm 1. This may be due to stress brought about by exaggerated behaviours of rams (e.g. aggression and chasing) during close confinement at lairage. However, more observations on-farm and at lairage are needed. Lastly, 69 loin samples of varying levels of residual glycogen were tested for drip loss, (WBC), fat, protein, and microbial content a day post-rigor (Day 1) and again after eight weeks (Week 8). Results showed no correlation between residual glycogen content and any of the parameters tested at either time points. A decrease in total glycosyl units at Week 8 was observed but no decrease in true glycogen levels. This was likely due to microbes use of free glucose as a food source. 

To conclude, the results of this study suggests that the co-habitation of intact rams and ewes on-farm causes stress, which is compounded by the close confinement at lairage, leading to high pHu of their carcasses. It is, therefore, recommended that, although intact rams have higher saleable weight, these rams be castrated before mixing with other rams and ewes to avoid high pHu and, hence, provide good quality meat and less stressed animals (better animal welfare). The fluctuation in muscle glycogen levels over time does also need closer scrutiny.

text: Identifying causes of high pH in lamb meat Lamb meat export is a multi-billion-dollar New Zealand industry. Therefore, strategies to maintain and improve quality have immediate commercial benefit. Consumers judge quality by colour, tenderness, and flavour, all of which are affected by ultimate pH (pHu). Ideal meat pHu is 5.5 and is influenced by muscle glycogen concentration. Insufficient muscle glycogen at slaughter results in high pHu (>5.8) which results in tough meat, dark colour, and shorter storage life. The decrease in meat pH post-slaughter is caused by the build-up of H+ ions as a consequence of anaerobic glycolysis of glycogen for ATP formation. Physical stress depletes muscle glycogen, prompting consumers to conclude animal mistreatment. However, stress, does not necessarily equate to abuse as all animals experience some level of pre-slaughter stress and any negative effects depend on duration, type, intensity, and susceptibility. Studies have focused on post-farm-gate stressors (e.g. transport and lairage) but less clear is the role of on-farm stressors on the incidence of high pHu. The aim of this study was to investigate the variation of muscle glycogen of lambs on-farm, examine the use of heat shock protein 20 (HSP20) as a marker for physiological stress, and determine any relationship between residual glycogen level and meat quality attributes such as water binding capacity (WBC), drip loss, microbial abundance, fat, protein, and water content.  

Two observations were conducted. Firstly, 60 animals from 2 farms with different production systems: wethers (castrated males) were raised with ewes in Farm 1, whereas, intact rams, wethers, cryptorchids, and ewes were all together and introduced at different times to the group in Farm 2.  These animals were biopsied two months before slaughter, a month before, and post-rigor. On-farm, large inter-individual variation in muscle glycogen was observed in both farms but no significant difference in true glycogen between farms. Muscle glycogen levels seemed to fluctuate from one biopsy to another, contrary to previous belief that it remains constant throughout. There was no significant difference in HSP20 between farms and no correlation between muscle glycogen and HSP20 was observed. Post-rigor, 66% of carcasses from Farm 2 had high pHu (≥5.8), compared to none from Farm 1. This may be due to stress brought about by exaggerated behaviours of rams (e.g. aggression and chasing) during close confinement at lairage. However, more observations on-farm and at lairage are needed. Lastly, 69 loin samples of varying levels of residual glycogen were tested for drip loss, (WBC), fat, protein, and microbial content a day post-rigor (Day 1) and again after eight weeks (Week 8). Results showed no correlation between residual glycogen content and any of the parameters tested at either time points. A decrease in total glycosyl units at Week 8 was observed but no decrease in true glycogen levels. This was likely due to microbes use of free glucose as a food source. 

To conclude, the results of this study suggests that the co-habitation of intact rams and ewes on-farm causes stress, which is compounded by the close confinement at lairage, leading to high pHu of their carcasses. It is, therefore, recommended that, although intact rams have higher saleable weight, these rams be castrated before mixing with other rams and ewes to avoid high pHu and, hence, provide good quality meat and less stressed animals (better animal welfare). The fluctuation in muscle glycogen levels over time does also need closer scrutiny.

year: 2018

title: Characterizing the cleaning process of chicken feathers.

authors: Sudalaiyandi, Ganesh

subjects: cleaning

abstract: Recently, there has been a surge in investigating the potential of using natural fibers for reinforcements in composite materials. One such natural fiber having immense potential for use in polymer composites is chicken feather fiber. Every year, over 4.8 million tonnes of chicken feathers are generated globally. Currently, feathers are hydrolyzed into feather-meal which is used as an animal feed and fertilizer. Chicken feathers are cheap, abundant and easily available. These feathers could be used as reinforcements in polymer composites. But, the feathers obtained from meat processing plants are coated with blood, offal fat, preen oil, debris and poultry processing water. This makes the feathers sticky, odoriferous and unfit for use as reinforcement. Extracting lipids from the feathers by leaching results in fibers which are not greasy and improves the fiber-matrix bonding of composites.

The objective of this study was to characterize the cleaning process of chicken feather fibers. Also, the effect of hydrogen peroxide cleaning on the mechanical properties of feather fiber was tested. The raw feathers were decontaminated with sodium hypochlorite and these samples were used for the cleaning experiments. Cleaning was carried out using 0.15 % and 0.25% of H₂O₂. Stages of cleaning and time were varied. The sample to solvent ratio was 10g/500 ml of solvent. It was found that 10 minutes of leaching for 3 stages was efficient in extracting soluble impurities from the feathers. Equilibrium experiments were conducted and a mass balance based on lipid exchange was designed. An equilibrium graph was plotted. Also, single fiber tensile tests were done on the H₂O₂ treated samples. A two parameter Weibull distribution was plotted to predict the failure strength of the fibers. It was found that H₂O₂ treatment on feathers reduces its Tensile strength (by very less magnitude). It was also observed that fibers were not damaged due to H₂O₂ treatment.

text: Characterizing the cleaning process of chicken feathers. Recently, there has been a surge in investigating the potential of using natural fibers for reinforcements in composite materials. One such natural fiber having immense potential for use in polymer composites is chicken feather fiber. Every year, over 4.8 million tonnes of chicken feathers are generated globally. Currently, feathers are hydrolyzed into feather-meal which is used as an animal feed and fertilizer. Chicken feathers are cheap, abundant and easily available. These feathers could be used as reinforcements in polymer composites. But, the feathers obtained from meat processing plants are coated with blood, offal fat, preen oil, debris and poultry processing water. This makes the feathers sticky, odoriferous and unfit for use as reinforcement. Extracting lipids from the feathers by leaching results in fibers which are not greasy and improves the fiber-matrix bonding of composites.

The objective of this study was to characterize the cleaning process of chicken feather fibers. Also, the effect of hydrogen peroxide cleaning on the mechanical properties of feather fiber was tested. The raw feathers were decontaminated with sodium hypochlorite and these samples were used for the cleaning experiments. Cleaning was carried out using 0.15 % and 0.25% of H₂O₂. Stages of cleaning and time were varied. The sample to solvent ratio was 10g/500 ml of solvent. It was found that 10 minutes of leaching for 3 stages was efficient in extracting soluble impurities from the feathers. Equilibrium experiments were conducted and a mass balance based on lipid exchange was designed. An equilibrium graph was plotted. Also, single fiber tensile tests were done on the H₂O₂ treated samples. A two parameter Weibull distribution was plotted to predict the failure strength of the fibers. It was found that H₂O₂ treatment on feathers reduces its Tensile strength (by very less magnitude). It was also observed that fibers were not damaged due to H₂O₂ treatment.

year: 2012

title: Precariat Māori households today

authors: Rua, Mohi

abstract: Aotearoa New Zealand is now the fifth most unequal economy in the OECD. To highlight the human cost of this situation, the concept of “the precariat” offers more informed and contextualised understandings of the situations of socio-economically marginalised people in Aotearoa. Significant societal and policy change is required for Māori whānau to be truly free from the cycle of precarity.

text: Precariat Māori households today Aotearoa New Zealand is now the fifth most unequal economy in the OECD. To highlight the human cost of this situation, the concept of “the precariat” offers more informed and contextualised understandings of the situations of socio-economically marginalised people in Aotearoa. Significant societal and policy change is required for Māori whānau to be truly free from the cycle of precarity.

year: 2019