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The major portion of Pacific whiting (PW) is commercialized in the form of frozen surimi. Alternative products for PW were investigated focusing on fresh surimi and texturized meat from PW mince. Fresh surimi is made without additives and kept refrigerated instead of frozen. Texturized meat is a meat-like product made from PW mince through freeze-texturization. Fresh surimi was stored at 5°C and analyzed for its total aerobic plate count (APC), shear stress, shear strain, and color during 7 days storage. Frozen surimi from PW was prepared with 0, 3, 6, and 9% cryoprotectants and was compared with fresh surimi for its gel forming ability. Fresh surimi had a shelf life of 5 days and the gel forming ability remained unchanged throughout storage time. Shear strain of fresh surimi was not different from frozen surimi with 9% cryoprotectants but shear stress was almost 3 times higher than the frozen one. Texturized meat from PW mince was prepared from unwashed or 1-washed mince kept frozen for 6-8 mo with or without the addition of 6% cryoprotectants. The minces were comminuted into a protein slurry, formed into patties, and frozen at -7, -18, and -50°C. The evaluations of ice formation (by microscopic study), hardness, cook loss, color, and water holding capacity were carried out during 20 days storage. The results showed that texturized meat with parallel layers was made from 1-washed PW mince. Unwashed PW mince created a sponge-like texture and had rapid quality deterioration, thus it is not recommended for this product. Cryoprotectants did not significantly affect the texture formation of the product and are not required to store mince as raw material for the texturized meat. The optimum freeze-texturized temperature for this product was -18°C or lower because it minimized quality changes during storage depending on the desirable texture. The lower the temperature (higher freezing rate), the finer the layers created. / Graduation date: 1996

Graduation date: 1984

Thesis (Ph.D.) - University of Queensland, / Includes bibliography.

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Thesis (MSc)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: Sunburn on apple and pear fruit results in large losses of export volumes in South African orchards. Producers estimate that losses due to sunburn are often about 10- 20%. Knowledge of temperature thresholds for sunburn as well as technologies available to manage sunburn is important to increase producer earnings. The effect of evaporative cooling on fruit surface temperature and sunburn was evaluated on 'Cripps' Pink', 'Royal Gala' and 'Fuji' apples as well as 'Forelle' pears. Evaporative cooling was effective in reducing fruit surface temperature by 0.6-3.7°C. Apple fruit under evaporative cooling treatments appeared to have acclimatised and had significantly higher surface temperatures when dry (0.9-4.7°C) than non-cooled fruit. This acclimitasing effect could be due to a modification of the cuticular wax layer. Futher trials are needed to investigate the cause of this acclimatising effect. The acclimatising effect was not found on 'Forelle' pears. Sunburn was reduced significantly only on 'Royal Gala' apples. Spraying 'Braeburn', 'Granny Smith', and 'Fuji' apples with reflective kaolin-based particle film (Surround WP) significantly reduced sunburn on 'Braeburn', 'Granny Smith' and 'Fuji' apple cultivars. Surround WP applications reduced leaf stomatal conductance and photosynthetic rate. Four applications of Surround WP with a commercial blower sprayer increased total soluble solids in 'Braeburn' . Four applications with a blower and five applications with a tower sprayer resulted in increased fruit size, higher flesh firmness, and lower percentage starch breakdown in 'Granny Smith'. Surround WP treatments slightly improved fruit colour in 'Granny Smith' apples. Futher trials are needed to establish whether Surround WP can,be reliably and economically removed from apple fruit and to evaluate the storage quality of fruit cleansed in this way. The effect of fruit surface temperatures (24°C, 30°C, 33-35°C, 40-43°C and 48-49°C) for increasing periods of time (two, four, six or eight hours) on maximum quantum yield of fluorescence (Fv/Fm) was measured on exposed and shaded sides of detached 'Cripps' Pink' and 'Royal Gala' apples. Measurements were taken directly after removal from the chamber as well as 12 hours later to assess recovery. Permanent damage to Photo system II (PSII) occurred between 48-49°C irrespective of duration, with permanent damage possible at 42-43°C when exposure exceeded six hours. There were no meaningful differences in Fv/Fm between shaded and exposed sides of apple fruit after exposure to high temperature. Duration of exposure was important in lowering PSU efficiency in 'Cripps' Pink' but less so in 'Royal Gala'. 'Cripps' Pink' apples harvested later in the season appeared to be able to recover from heat stress better than apples harvested earlier in the season. However, we only studied the effects of high temperature on apple tissues. More research is needed to establish the reaction of apple tissues to high temperatures in the presence of sunlight. / AFRIKAANSE OPSOMMING: Sonbrand op appel en peervrugte kom jaarliks voor in Suid-Afrikaanse boorde en lei tot groot afnames in vrugte wat geskik is vir die uitvoermark. Produsente beraam dat verliese a.g.v. sonbrand jaarliks 10-20% beloop. Kennis van drempelwaarde temperature vir die ontwikkeling van sonbrand sowel as die tegnologieë wat beskikbaar is om sonbrand te bekamp, is van groot belang om uitpakke te verbeter. Die effek van oorhoofse besproeïng op vrugtemperature en sonbrand van 'Cripps' Pink', 'Royal Gala' en 'Fuji' appels sowel as 'Forelle' pere is ondersoek. Oorhoofse besproeïng het vrugtemperature betekenisvol verlaag in al die proewe. Dit wil voorkom of appels onder oorhoofse besproeïng geakklimatiseer het en dié appels het hoër skil temperature geopenbaar wanneer hulle droog was as die kontrole vrugte. Moontlik is die effek te wyte aan 'n verandering in die kutikulêre waslaag. Verdere proewe om hierdie verskynsel te probeer verklaar is nodig. Die effek is nie waargeneem op die 'Forelle' pere nie. Sonbrand is betekenisvol verminder op 'Royal Gala' appels. Toediening van weerkaatsende kaolin-gebaseerde partikels (Surround'" WP) het sonbrand betenisvol verlaag op 'Braeburn' , 'Granny Smith', en 'Fuji' appels. Surround® WP toedienings het blaarhuidmondjie-geleiding en die tempo van fotosintese verlaag. Vier toedienings van Surround® WP met 'n kommersiële waaierblaser het totale oplosbare vastestowwe (TOVS) beduidend verhoog in 'Braeburn' appels. Vier toedienings met 'n waaierblaser en vyf toedienings met 'n toring spuitkar het gelei tot 'n verhoging in vrugmassa en vrugferrnheid, en 'n verlaging in persentasie styselafbraak in 'Granny Smith' appels. Surround® WP toedienings het gelei tot effens beter kleur op 'Granny Smith' appels. Verdere proewe is nodig om te bepaal of Surround® WP op 'n betroubare en ekonomiese wyse van vrugte verwyder kan word in die pakstoor, en wat die hou-vermoë is van appels wat só behandel is. Die effek van vrugoppervlaktemperature (24°C, 30°C, 33-35°C, 40-43°C en 48-49°C) vir toenemende tydsdure (twee, vier, ses en agt ure) op maksimum kwantum-opbrengs van fluoressensie is gemeet op sonkante en skadukante van geplukte 'Cripps' Pink' en 'Royal Gala' appels. Metings is geneem direk na verwydering uit die oonde sowel as 12 ure later om moontlike herstel waar te neem. Permanente skade aan Fotosisteem II (PSII) het plaasgevind tussen 48-49°C ongeag tydsduur, met permanente skade ook moontlik by 42-43°C wanneer blootstelling aan genoemde temperature ses ure oorskry het. Daar was geen betekenisvolle verskille in Fv/Fm tussen skadu- en sonkante van appels na blootstelling aan hoë temperature nie. Die tydsduur van blootstelling was belangrik om PSII effektiwiteit te verlaag in 'Cripps' Pink', maar minder so in 'Royal Gala'. Dit wil voorkom of 'Cripps' Pink' appels later in die seisoen beter daartoe in staat is om te herstel van hitte stres as vroeër in die seisoen. Ons het egter slegs die effek van hoë temperature op appel weefsels ondersoek. Verdere proewe is nodig om die reaksie van appelweefsels op hoë temperature in die teenwoordigheid van sonlig te ondersoek.

The physiological ecology of five coastal species has been examined with respect to temperature and its effect on survival and distribution. The aims of the study have been to establish whether any direct correlation exists between distribution and the responses of the plants to temperature at different stages in the life cycle. The species Tinder consideration were the northern Ligusticum scoticum and Mertensia maritima and the southern Crithmum maritimum, Limonium binervosum and Glaucium flavum. Highest germination percentages for each species were found at temperatures close to those associated with the season favourable for germination in the natural habitat. Northern species had higher temperature requirements than the southern, corresponding to spring/ summer and autumn or spring germination respectively. Root respiration, measured as oxygen uptake, was found to be twice as great in the northern Ligusticum and Mertensia as in the southern Crithmum and Limonium over a range of experimental temperatures. This varied to some extent with time and temperature of pretreatment. The single experiment on the southern Glauci.um showed rates similar to those of the northern species. Arrhenius plots' of respiration data for the northern species showed a break in gradient at the upper end of the experimental temperature range which correlated well with apparently limiting July mean temperatures from the distribution maps. The southern Crithmum showed a break at lower temperature range close to the limiting January mean temperature. The response of Limonium to experimental temperature depended on the pretreatment; upper range breaks were shown after low pretreatment temperatures, and lower range breaks after higher pretreatment temperatures. The single experiment on Glaucium gave a straight line Arrhenius plot. Carbohydrate analyses of the same pretreated plants yielded additional information relevant to the survival and thus to the distribution in relation to temperature. The southern Crithmum had the highest starch content at all temperatures while the northern Ligusticum and Mertensia had less. Ratios of soluble sugar to starch were greatest in the northern species, possibly reflecting displacement of the equilibrium from starch to soluble sugar at lower temperatures. Overall a connection has been demonstrated between the direct effects of temperature on the plants and the limitation of distribution by temperature. This is clearest for the two northern species, Ligusticum scoticum and Mertensia maritima, less definite for the southern Crithmum maritimiim, and only suggested for Limonium binervosum with its apparently less simple temperature responses. Glaucium flavum appears anomalous and requires further study.

This thesis investigates physiological mechanisms underlying temperature adaptations in perennial grasses. A comparative approach was employed by using pairs of species that have been collected from lowland sites in thermally contrasting habitats up to 2000 km apart on a north-south direction. The population samples from northern latitudes, i.e. from cooler climates, had higher growth rates at 12°C than southern provenances. Dark respiration rates between 5 and 25°C did not differ between provenances; but acclimatization at 10°C increased the respiration rate in all northern population samples, whereas some southern population samples reduced their respiration rate as a response to acclimatization at 10°C. Northern provenances showed a greater activity of carbohydrate formation in light after periods of 48 hours starvation in darkness. This property could be attributed to the higher activity of RuBP-carboxylase in northern genotypes. No evidence was found that the higher activities are due to higher enzyme concentrations in these genotypes. The enzyme exhibited lower energies of activation in northern provenances in the range 5 - 15°C Activation energies for succinate dehydrogenase in isolated mitochondria were higher for northern population samples in the range 10 - 25°C. Higher specific activities were found for malate dehydrogenase from northern plants between 5 and 25°C. In this temperature range the apparent energies of activation were lower for northern plants. The enzyme displayed positive thermal modulation in both northern and southern provenances. Temperature changes had generally a greater effect on northern provenances. The significance of these findings is discussed in the light of previous reports in the literature and in relation to a possible advantage in the plant's native habitat.