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Item 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 NormanBruising 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.Item Prediction and quantification of apple bruising : a thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Agricultural Engineering at Massey University, Palmerston North, New Zealand(Massey University, 1993) Pang, David WeilongMechanical handling subjects fruit to impacts which often cause bruising. Such bruising is a major source of quality loss in the fruit industry. In this study, a range of experiments was carried out to investigate the quantification of bruises and the prediction of bruising in relation to mechanical handling systems. In order to understand apple bruising, a study of free normal impact between pairs of apples was conducted. There was a 2/5 power relationship between contact area and impact energy. The coefficient of restitution varied in a non-linear manner with impact energy, decreasing as impact energy increased. Bruise damage produced by a typical New Zealand-made fruit grader was critically analysed. A large percentage of individual bruises was under 1 cm2 in area and it was rare to have any bruises above 3 cm2. The total number of bruises was found to be the best indicator of bruise susceptibility. A new method of predicting such bruises has been developed involving a new term, the Bruise Factor, which was related to bruising sustained during handling operations, allowing for the variation in fruit size, shape and mass. An Instrumented Sphere (IS) was used to characterize impacts on commercial packing lines. It was found that the IS could be used to identify apple-to-apple impacts likely to cause bruising in commercial packing operations, providing care is taken with interpretation of the data. Typical impacts on packing lines were represented by impacts onto a flat steel surface, a rubber pad, a plastic tube, a solid plastic bar, and onto another fruit. Impact tests were conducted on freshly picked Gala, Splendour, Fuji, Braeburn, and Granny Smith apples, all grown in Hawkes Bay, New Zealand. Bruise areas produced by impact onto flat steel, rubber, plastic tubing, and a solid plastic bar were found to be linearly correlated with the peak acceleration recorded by an Instrumented Sphere dropped from the same heights. Following fruit-to-fruit impacts, bruising was generally more severe on one of the two apples. When the results of apple-to-apple and IS-to-apple impacts were compared, it was found that the area of the larger of the two bruises produced in fruit-to-fruit impacts was directly related to the peak acceleration recorded by the IS when it was dropped onto a fruit from the same height. For each variety and each surface the drop height required to produce a critical bruise with a surface area of 1 cm2 (as measured with the skin removed) was determined. By joining the threshold points on each surface response line, a threshold potential bruise boundary was formed on a velocity change against peak acceleration graph. The boundary curve, which included apple-to-apple impact, was hyperbolic in shape, rather than the linear boundary described in other studies. The implications of the results to the fruit industry are discussed in this study.