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Objective meat quality, composition and sensory profiling of New Zealand lamb from different production systems : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Animal Science at Massey University, Palmerston North, New Zealand
(Massey University, 2022) Ye, Yangfan
Lamb production systems in New Zealand can vary widely in animal characteristics such as breed, sex, diet and age at slaughter. In order to move towards production systems that are more consumer-focused, there is a need to understand meat quality characteristics and cross-cultural consumer preference of loins from lambs reared under a wide range of commercial production systems. This thesis conducted a comprehensive assessment of the loins (M. longissimus thoracis) of 150 lambs from 10 forage production systems (n=15) and assessed meat quality, fatty acid composition, volatile and proteomics profiles, and consumer sensory evaluations. Instrumental measurement of meat quality (shear force, pH, colour, and water holding capacity) showed that animal age at slaughter and diet had a greater effect on meat quality than the sex of the lamb. A chicory diet increased carcass weight (CW) of lambs resulting in a greater loin intramuscular fat (IMF) percentage compared to a perennial ryegrass diet (18.1±0.1kg vs. 16.9±0.1kg CW and 2.0-2.6% vs. 1.3-1.6% IMF, respectively). Finishing lambs in New Zealand forage systems for 12 months resulted in lower proportions of n-3 fatty acids in meat as well as a lower PUFA:SFA ratio compared to lambs slaughtered at 4- or 8-month-old (2.93-3.41% vs. 4.79-5.86% n-3 fatty acids and 0.17-0.19 vs. 0.27-0.35 PUFA:SFA, respectively). Of the 286 proteins identified among the raw lamb loins, only 17 showed significant differences in abundance between production systems which indicated that the expression of proteins was rarely affected by the production factors. For both New Zealand and Chinese consumers, the average liking scores differed among the different types of commercial lambs. Consumer clusters showed that the fatty acid profile and the volatile compounds derived from lipid oxidation seem to be a stronger driver of consumer liking of lamb for some consumers than others.
The signal-based microbial spoilage on New Zealand export lamb : thesis submitted to Massey University for the degree of Doctor of Philosophy
(Massey University, 2019) Zhang, Yufeng
Lamb is one of New Zealand’s primary exports; however, the spoilage of lamb causes considerable financial loss. Psychrotolerant, anaerobically growing spoilage bacteria are responsible for the spoilage of fresh chilled vacuum-packaged lamb exported from New Zealand. These spoilage bacteria interact with through a system called “quorum sensing”. Different types of quorum sensing signals are produced by spoilage bacteria in response to the bacterial cell population. Through this cell-to-cell interaction, the expression of certain genes is regulated, followed by changes in bacterial activity. The main objective of this research was to determine the influence of quorum sensing signals produced by those psychrotolerant, anaerobically growing spoilage bacteria on the spoilage of New Zealand lamb. Quorum sensing of psychrotolerant, anaerobically growing spoilage bacteria was studied using in vitro and ex vivo methods. Two types of in vitro quorum sensing signals (Type-I and Type-II) were identified for New Zealand reference type strains Hafnia alvei and Serratia liquefaciens, and Type-II quorum sensing signal was found from a lamb isolate Carnobacterium divergens. These two types of signals were also discovered in spoiled chilled vacuum-packed lamb. After random EZ-Tn5 transposon mutagenesis to luxI/R-type genes and luxS genes, which are responsible for Type-I and Type-II signals respectively in H. alvei, S. liquefaciens, and C. divergens, wild type and mutant strains were compared. Type-I quorum sensing signaling molecules influenced the expression of lipB that regulates the secretion of hydrolytic enzymes produced by H. alvei and S. liquefaciens. These enzymes are believed to contribute to lamb spoilage. Cinnamaldehyde added to fresh vacuum-packed New Zealand lamb as an inhibitor of quorum sensing enabled an extension of the shelf-life of lamb by 2-8 days, through deactivating the Type-I quorum sensing system. Inhibition of quorum sensing has the potential in lamb preservation.
Investigating the relationship between lamb weaning age and forage diet on carcass and meat quality : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science, Massey University, Palmerston North, New Zealand
(Massey University, 2019) Kok, Jacobus Christiaan
Lamb carcass characteristics and meat quality are important components of the value chain that determine the carcass value and price obtained. On-farm factors can affect carcass characteristics and meat quality of lamb, however, the effect of early weaning and forage diet on carcass and meat quality characteristics is not well-known. Therefore, this thesis considers the relationship between weaning age and the forage diet for influencing carcass characteristics and meat quality of lamb. The study compared carcass characteristics and meat quality of early weaned lambs (at eight weeks of age) grazing a plantain-clover mix, and conventionally weaned lambs (at 14 weeks of age) grazing a plantain-clover mix or perennial ryegrass-white clover pasture with all lambs finished for six weeks as one mob on perennial ryegrass-white clover pasture to achieve a target minimum live weight of 35 kg at slaughter (Chapter 3). Forty-three Romney ewes rearing twin lambs (86 lambs) were used in this study. Ewes and their lambs were allocated to one of four treatments: 1) lambs weaned early (eight weeks of age) on a plantain-clover mix (EARLY), 2) lambs with dam grazing a plantain-clover mix (HERB), 3) lambs with dam grazing perennial ryegrass-white clover pasture >1200 kgDM/ha (HIGH), and 4) lambs with dam grazing perennial ryegrass-white clover pasture <1200 kgDM/ha (LOW). Lambs in treatments 2, 3, and 4 were weaned at 14 weeks of age. Lambs in the HERB treatment had the fastest growth rate, yielding heavier carcasses and a higher dressing out percentage compared to EARLY and LOW lambs. HIGH lambs had intermediate growth rates, carcass weights and dressing out % (Chapter 5, Table 8). Physical dissection of the hind leg showed lambs in the EARLY treatment had the least dissectible fat compared to HIGH and LOW lambs which had the most, with HERB lambs intermediate. In addition, lambs in the EARLY treatment had a similar fat% and muscle% compared to HERB and LOW lambs but produced lower fat% and higher muscle % than lambs in the HIGH treatment (Chapter 5, Table 9). Objective measurements of lamb meat quality only showed a difference among treatments for sarcomere length and total shear force work (Chapter 5, Table 10). Lambs in the EARLY and HIGH treatments had the longest sarcomere lengths and lambs in the HERB treatment the shortest, with intermediate lengths recorded for LOW lambs. Meat from lambs in the EARLY, HERB and LOW treatments required less total shear force work than lambs in the HIGH treatment. Although statistically significant the relative difference in results was not substantial, indicating that generally the treatments had no effect on meat quality. Early weaning of lambs onto a plantain-clover mix does not have negative effects on carcass and meat quality. However, the slower growth rate of early weaned and restricted perennial ryegrass pasture raised lambs resulted in lower carcass weights in this study indicating that a lower nutritive diet as a consequence of using grass species or a lack of milk intake will mean lambs will need more time to achieve a set finishing weight.
Effects of early weaning onto herb-clover mix on lamb carcass and meat quality characteristics : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Animal Science at Massey University, Palmerston North, New Zealand
(Massey University, 2019) Wong, Huai Xuan
After eight weeks of age, the lambs’ diet consists of only a small proportion of milk. Early weaning at 8-weeks of age onto high nutritive value forage crops, therefore, may be able to compensate for the removal of milk from the diet whilst maintaining lamb liveweight gains. It is crucial, however, to ensure there are no negative effects of early weaning on the yield of saleable meat and its quality. This study aimed to understand the effects of early weaning onto a herb-mix on carcass and meat quality characteristics. Ewes and their twin lambs (weighing at least 16kg) were allocated to one of three treatments: 1. Lambs with dams on grass (GRASS) (lambs; n=50; 𝑥̅ LW=17.0kg), 2. Lambs with dams on herb-mixes (HERB) (lambs; n=50; 𝑥̅ LW=17.2kg), 3. Lambs weaned onto herb-mixes (56-days old) and dams on grass (EARLY) (lambs; n=50; 𝑥̅ LW=16.4kg). At 12 weeks of age, all lambs were weaned and lambs with a liveweight of greater than 35kg were sent for slaughter (n=28; 𝑥̅ LW=36.9kg). The remaining lambs grazed together on ryegrass-based pasture for six weeks. After this period, lambs with a liveweight >35kg were sent for slaughter (n=93; 𝑥̅ LW=40.4). Hot-carcass weight and VIAscan estimates of GR soft tissue depth (tissue depth 110 mm from the midline on the 12th rib) and lean meat yields were obtained. Meat quality assessments were conducted to obtain pH, colour, water-holding capacity, intramuscular fat, sarcomere length and tenderness values. The average daily gain of lambs in the HERB treatment (307.0 ± 7.4g) were greater than those in the EARLY (255.8 ± 8.0g) and GRASS (267.8 ± 8.5g) treatments (P<0.05). The dressing out and lean meat yield did not differ among lambs of different treatments (P>0.05). The lambs in HERB treatment had greatest hot-carcass weight (17.4 ± 0.23kg) and GR soft tissue depth (8.2 ± 0.41mm) (P<0.05). The higher average daily gains, carcass weight and GR soft tissue depth of lambs on herb-mix is expected as it has a higher feeding value. Lambs in EARLY treatment had the greatest bone weight (P<0.05). Dissected fat weight, muscle-to-bone ratio and muscularity index was greatest in lambs from the HERB treatment (P<0.05). There was no difference across the treatments for intramuscular fat percentage, meat colour, drip loss, sarcomere length and shear force values (P>0.05). All treatments were associated with low shear force values (<5kg F). The results suggest that, when taken to a set weight, early weaning of lambs onto herb-clover mix did not appear to have any negative effects on carcass and meat quality characteristics. However, a smaller proportion of early weaned lambs may achieve a set slaughter weight at a set date compared to similar lambs with their dams on a high nutritive value forage. Early weaned lambs are likely to require more time for finishing to a set weight.
In-plant, non-invasive spectral imaging for the prediction of lamb meat quality attributes : a thesis presented to Massey University for the partial fulfilment of the requirements of the degree of Masters of Food Technology, Massey University, Manawatū, New Zealand
(Massey University, 2016) Stuart, Adam Douglas
Muscle foods such as meat are a perishable, nutritious, relatively expensive food commodity, a great source of human nutrition and are a large part of the New Zealand economy, as well as overseas. Currently, New Zealand’s meat producing companies measure meat quality attributes by using a different technology for every trait, with no overarching way to combine them, with many of the technologies requiring collection and destruction of the product. There is a desire by the meat industry to find a single way to measure and compare meat quality parameters in a single process or technology. The development of an in-line (within the normal production line of an abattoir or meat processor), real time, non-destructive quality control system could help define multiple meat traits in a way that can guarantee the product in terms of composition, safety and consistency. These guarantees not only help the producer to ask a higher premium for their product, but also give assurances to the consumer that they are getting exactly what they are expecting and paying for. This thesis focused on determining whether the spectral imaging technologies of near infrared and hyperspectral imaging, and relevant pre-processing and modelling techniques were suitable for use in an in-plant situation for the prediction of lamb meat quality attributes. Data was collected on 2511 lambs from 10 separate kills. The lambs were slaughtered through three abattoirs owned by Alliance Group Limited with near infrared and hyperspectral imaging of intact M. Longissimus thoracis et lumborum muscle surface collected at 24 hours post-mortem. Traditional meat quality measurements were also collected; tenderness using a MIRINZ tenderometer, CIELab colour using a CR-400 colour meter, ultimate pH using an Eutech Cyberscan pH 300 meter, marbling using subjective scoring by trained personnel and intramuscular fat content using gas chromatography – flame ionisation detector. The resulting data were split and used to generate calibration and validation data sets. The calibration data was used together with the spectral data that was processed using a variety of chemometric techniques including partial least squares, variable selection and neural networks to generate predictive models. The accuracy of the predictive models was then tested using the validation data set. This work found that not all meat quality traits were able to be predicted accurately and certain techniques worked better for differing traits. The best predictive models for ultimate pH using the near infrared and hyperspectral data achieved R2 values (a measure of goodness of fit) from the validation data sets of 0.63 and 0.48 respectively. For near infrared the best predictive models were achieved using partial least squares with pre-processing (standard normal variate, orthogonal signal correction and mean centring) applied, while for hyperspectral imaging neural networks provided the best model using a decay of 0.00004 and a node size of 2. The best predictive models for intramuscular fat using the near infrared and hyperspectral data achieved R2 values from the validation data sets of 0.56 and 0.75 respectively. For near infrared this was achieved using partial least squares with pre-processing (normalisation, multiplicative scatter correction and mean centring) applied, while for hyperspectral imaging neural networks provided the best model using a decay of 0.0009 and a node size of 4. This performance of these two traits in particular, shows that that the prediction abilities are of a quality that future work on implementing these into an in-line system at a pilot scale should be considered. Overall, the use of novel modelling techniques such as neural networks showed potential to increase the predictive abilities of the resulting models, over more traditional modelling techniques. Additionally, it was demonstrated that the number of predictors needed to create a calibration model could be reduced, increasing the speed of analysis with only minimal loss in the accuracy of the resulting model. Results obtained during this study suggest that the calibration models are not abattoir dependent and the transfer of one calibration model to multiple abattoirs could decrease the costs and allow for faster development and implementation of an in-line, in-plant system.
Effects of different freezing/thaw-ageing regimens on physicochemical, biochemical characteristics and meat quality attributes of lamb loins : a thesis presented to Massey for the partial fulfilment of the requirements of the degree of Masters of Food Technology, Massey University, Manawatū, New Zealand
(Massey University, 2015) van der Stok, Carolijn Henrick Marie
New Zealand red meat is in demand around the world; consumers recognise the safe, healthy, clean and green values of New Zealand’s pasture-raised beef lamb and venison. Meat is transported chilled in containers to overseas markets, and recently container ships have started to travel slower to reduce fuel consumption. This has resulted in the meat spending longer in the containers, meaning that key quality attributes of lamb cannot be guaranteed anymore. Finding an alternative method to provide the overseas consumers with chilled meat of the required quality is a top priority for the industry. Currently during container transport, meat is ageing for 6/8 weeks but with the newly introduced longer transport time to overseas markets it is too long for the meat in terms of food quality. Frozen meat is traditionally aged first before freezing. Previous observations show that 2 weeks ageing for lamb is enough to give equivalent quality attributes to the meat as ageing for 8 weeks. In the current study meat is frozen first and then thawed-aged and it was therefore hypothesised that by increasing the thawing-ageing temperature the ageing process could be accelerated. This thesis focused on determining the effects of different freezing/thawing-ageing regimens on meat quality and physical and biochemical characteristics of lamb loins. To study the effect of the different regimens, 10 treatments were set up and 90 loins in total have been used. The loins were randomly assigned to three different freezing conditions named Slow Freezing (SF), Fast Freezing (FF) and Very Fast Freezing (VFF) followed by three different thaw/ageing regimens: -1.5°C, 1°C and 3.5°C. A control group was included as treatment number 10, the Control group represents a non-frozen treatment with only 2 weeks of ageing. The effects on the quality of the loins were evaluated through the use of quality measurements such as pH, colour, water holding capacity, tenderness and lipid oxidation. Other analyses used to give an indication of the mechanisms for any quality differences were histology and metabolomics. The data suggest that FF and VFF resulted in a greater water-holding capacity and colour stability than SF. Ageing at 3.5°C showed a general trend for accelerated lipid oxidation compared with ageing at -1.5°C and 1°C. SF seems to contribute to damage along the fibre whereas FF and VFF show obvious holes within the fibres. These different types of damage may lead to lesser or varying meat quality. Overall, this work found that FF and VFF showed benefits over SF in several aspects of meat quality, but the differences were small. The results also suggest that FF or VFF could be used to avoid some of the common quality defects associated with freezing first and then thaw-ageing. This may potentially provide an opportunity for the New Zealand meat industry to utilise frozen storage/shipping and so saving money while still meeting the consumer demands for high quality fresh meat.
The ageing of bruises in lambs : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Massey University
(Massey University, 1983) Thornton, Ronald Norman
Bruising in lambs processed for human consumption is a significant economic problem. A reduction in the prevalence of bruises could be achieved relatively efficiently if their important places of occurrence could be identified by ageing these lesions with respect to the known times of occurrence of events of possible aetiological significance. To this end efforts were made to age experimental bruises in lambs by objectively assessing semi-quantitative histopathological data using a mathematical model based on Bayes' theorem of inverse probabilities, by enzyme histochemical and isoelectric focussing studies and by measurement of muscle pH. The Bayesian method for objective histopathological ageing was developed and tested on data representing 178 bruises. It was successful in identifying bruises as either 1-20 hours or more than 24 hours old. The 'accuracy' with which a bruise of known age could be identified as such depended on the nature and number of tissue samples studied. The degree of 'confidence' with which an individual bruise of unknown age could be aged, however, depended both on the 'accuracy' of the method and on the relative number of bruises estimated to belong to each of the two age categories considered. In general a degree of 'confidence' of 80-90% can be expected in practice, and in this respect the performance of the Bayesian method is superior to that achieved by purely subjective means. A pilot survey involving 107 bruises collected from an export meat works established both the practical value of the objective ageing method and its superiority over alternative epidemiological approaches to the problem of utilising data pertaining to trucking times and holding times in meat works yards. Of the bruises studied, 60% were estimated to have been inflicted within the works, and 40% prior to arrival. Enzyme studies on bruises aged 4-144 hours old revealed no detectable relationships between observed changes in either histochemical or isoenzyme activities and bruise ages. In light of contradictory published results pertaining to other types of wounds, this lack of success was thought to reflect the relatively mild nature of the tissue reaction in bruises. Statistically significant relationships could not bo demonstrated between absolute or relative muscle pH and the ages of bruises from 4-48 hours old. A newly recognised condition of 'subcutaneous haemorrhagic speckling' in the carcase adipose tissue of young lambs processed for human consumption was investigated. From histopathological and epidemiological evidence, the primary cause of the lesions was shown to be electrical stunning. However, secondary aetiological factors were proposed as having influenced the prevalence and severity of lesions. Attempts to elucidate the pathogenesis of 'speckling' with the intention of formulating a rational approach to its prevention were unsuccessful.

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