The effect of post harvest handling on selected native food plants

A commercial issue currently facing native plant food producers and food processors, and identified by the industry itself, is that of delivering quality products consistently and at reasonable cost to end users based on a sound food technology and nutrition platform. A literature survey carried out in July 2001 by the DPI&F’s Centre for Food Technology, Brisbane in collaboration with the University of Queensland to collect the latest information at that time on the functional food market as it pertained to native food plants, indicated that little or no work had been published on this topic. This project addresses two key RIRDC sub program strategies: to identify and evaluate processes or products with prospects of commercial viability and to assist in the development of integrated production, harvesting, processing and marketing systems. This project proposal also reflects a key RIRDC R&D issue for 2002-2003; that of linking with prospective members of the value chain. The purpose of this project was to obtain chemical data on the post harvest stability of functional nutritional components (bio actives) in commercially available, hand harvested bush tomato and Kakadu plum. The project concentrated on evaluating bioactive stability as a measure of ingredient quality.

The Effect of Post-Pubertal Castration on Behaviour in Beef Cattle

Castration of male beef cattle is advantageous for management, however pre-pubertal (early) castration results in comparative losses in growth rate (Jago et al., 1996). Post-pubertal (late) castration may maintain growth rate but lead to management problems. The behavioural differences between early castrates (9mo) and late castrates (18mo), which may have an effect on growth rate were studied.

The effect of post-weaning growth on the fertility of Brahman cross heifers

In the dry tropics of northern Australia heifers are generally weaned mid-year at about six months of age and experience two dry seasons and a wet season prior to first mating at 2 years of age when only 60% are likely to conceive (Entwistle 19830. Pre-mating liveweight (PMLW) explains much of the variation in conception rate, but year effects explain further variations (Rudder et al 1985).

The risk of pollen-mediated gene flow from exotic Corymbia plantations into native Corymbia populations in Australia

Sectors of the forest plantation industry in Australia are set to expand in the near future using species or hybrids of the spotted gums (Corymbia, Section Politaria). Plantations of these taxa have already been introduced across temperate and subtropical Australia, representing locally exotic introductions from native stands in Queensland and New South Wales. A literature review was undertaken to provide insights into the potential for pollen-mediated gene flow from these plantations into native populations. Three factors suggest that such gene flow is likely; (1) interspecific hybridisation within the genus has frequently been recorded, including between distantly related species from different sections, (2) apparent high levels of vertebrate pollinator activity may result in plantation pollen being moved over hundreds of kilometres, (3) much of the plantation estate is being established among closely related taxa and therefore few barriers to gene flow are expected. Across Australia, 20 of the 100 native Corymbia taxa were found to have regional level co-occurrence with plantations. These were located most notably within regions of north-east New South Wales and south-east Queensland, however, co-occurrence was also found in south-west Western Australia and eastern Victoria. The native species found to have co-occurrence were then assessed for the presence of reproductive barriers at each step in the process of gene flow that may reduce the number of species at risk even further. The available data suggest three risk categories exist for Corymbia. The highest risk was for gene flow from plantations of spotted gums to native populations of spotted gums. This was based on the expected limited existence of pre- and post-zygotic barriers, substantial long-distance pollen dispersal and an apparent broad period of flowering in Corymbia citriodora subsp. variegata plantations. The following risk category focussed on gene flow from Corymbia torelliana × C. c. variegata hybrid plantations into native C. c. variegata, as the barriers associated with the production and establishment of F1 hybrids have been circumvented. For the lowest risk category, Corymbia plantations may present a risk to other non-spotted gum species, however, further investigation of the particular cross-combinations is required. A list of research directions is provided to better quantify these risks. Empirical data will need to be combined within a risk assessment framework that will not only estimate the likelihood of exotic gene flow, but also consider the conservation status/value of the native populations. In addition, the potential impacts of pollen flow from plantations will need to be weighed up against their various economic and environmental benefits.

Effect of soil burial depth and wetting on mortality of diapausing larvae and patterns of post-diapause adult emergence of sorghum midge, Stenodiplosis sorghicola (Coquillett) (Diptera: Cecidomyiidae)

In south-eastern Queensland, Australia, sorghum planted in early spring usually escapes sorghum midge, Stenodiplosis sorghicola, attack. Experiments were conducted to better understand the role of winter diapause in the population dynamics of this pest. Emergence patterns of adult midge from diapausing larvae on the soil surface and at various depths were investigated during spring to autumn of 1987/88–1989/90. From 1987/88 to 1989/90, 89%, 65% and 98% of adult emergence, respectively, occurred during November and December. Adult emergence from larvae diapausing on the soil surface was severely reduced due to high mortality attributed to surface soil temperatures in excess of 40°C, with much of this mortality occurring between mid-September and mid-October. Emergence of adults from the soil surface was considerably delayed in the 1988/89 season compared with larvae buried at 5 or 10 cm which had similar emergence patterns for all three seasons. In 1989/90, when a 1-cm-deep treatment was included, there was a 392% increase in adult emergence from this treatment compared with deeper treatments. Some diapausing larvae on the surface did not emerge at the end of summer in only 1 year (1989/90), when 28.0% of the larvae on the surface remained in diapause, whereas only 0.8% of the buried larvae remained in diapause. We conclude that the pattern of emergence explains why spring plantings of sorghum in south-eastern Queensland usually escape sorghum midge attack.

Investigation of movement and factors influencing post-release survival of line-caught coral reef fish using recreational tag-recapture data

Six species of line-caught coral reef fish (Plectropomus spp., Lethrinus miniatus, Lethrinus laticaudis, Lutjanus sebae, Lutjanus malabaricus and Lutjanus erythropterus) were tagged by members of the Australian National Sportsfishing Association (ANSA) in Queensland between 1986 and 2003. Of the 14,757 fish tagged, 1607 were recaptured and we analysed these data to describe movement and determine factors likely to impact release survival. All species were classified as residents since over 80% of recaptures for each species occurred within 1 km of the release site. Few individuals (range 0.8-5%) were recaptured more than 20 km from their release point. L. sebae had a higher recapture rate (19.9%) than the other species studied (range 2.1-11.7%). Venting swimbladder gases, regardless of whether or not fish appeared to be suffering from barotrauma, significantly enhanced (P < 0.05) the survival of L. sebae and L. malabaricus but had no significant effect (P > 0.05) on L. erythropterus. The condition of fish on release, subjectively assessed by anglers, was only a significant effect on recapture rate for L. sebae where fish in "fair" condition had less than half the recapture rate of those assessed as in "excellent" or "good" condition. The recapture rate of L. sebae and L. laticaudis was significantly (P < 0.05) affected by depth with recapture rate declining in depths exceeding 30 m. Overall, the results showed that depth of capture, release condition and treatment for barotrauma influenced recapture rate for some species but these effects were not consistent across all species studied. Recommendations were made to the ANSA tagging clubs to record additional information such as injury, hooking location and hook type to enable a more comprehensive future assessment of the factors influencing release survival.

Sorghum stay-green QTL individually reduce post-flowering drought-induced leaf senescence

Sorghum is an important source of food, feed, and biofuel, especially in the semi-arid tropics because this cereal is well adapted to harsh, drought-prone environments. Post-flowering drought adaptation in sorghum is associated with the stay-green phenotype. Alleles that contribute to this complex trait have been mapped to four major QTL, Stg1-Stg4, using a population derived from BTx642 and RTx7000. Near-isogenic RTx7000 lines containing BTx642 DNA spanning one or more of the four stay-green QTL were constructed. The size and location of BTx642 DNA regions in each RTx7000 NIL were analysed using 62 DNA markers spanning the four stay-green QTL. RTx7000 NILs were identified that contained BTx642 DNA completely or partially spanning Stg1, Stg2, Stg3, or Stg4. NILs were also identified that contained sub-portions of each QTL and various combinations of the four major stay-green QTL. Physiological analysis of four RTx7000 NILs containing only Stg1, Stg2, Stg3, or Stg4 showed that BTx642 alleles in each of these loci could contribute to the stay-green phenotype. RTx7000 NILs containing BTx642 DNA corresponding to Stg2 retained more green leaf area at maturity under terminal drought conditions than RTx7000 or the other RTx7000 NILs. Under post-anthesis water deficit, a trend for delayed onset of leaf senescence compared with RTx7000 was also exhibited by the Stg2, Stg3, and Stg4 NILs, while significantly lower rates of leaf senescence in relation to RTx7000 were displayed by all of the Stg NILs to varying degrees, but particularly by the Stg2 NIL. Greener leaves at anthesis relative to RTx7000, indicated by higher SPAD values, were exhibited by the Stg1 and Stg4 NILs. The RTx7000 NILs created in this study provide the starting point for in-depth analysis of stay-green physiology, interaction among stay-green QTL and map-based cloning of the genes that underlie this trait.

Value-adding Australian sardines: Factors affecting rates of deterioration in sardine (Sardinops sagax) quality during post-harvest handling

Deficiencies in sardine post-harvest handling methods were seen as major impediments to development of a value-adding sector supplying Australian bait and human consumption markets. Factors affecting sardine deterioration rates in the immediate post-harvest period were investigated and recommendations made for alternative handling procedures to optimise sardine quality. Net to factory sampling showed that post-mortem autolysis was probably caused by digestive enzyme activity contributing to the observed temporal increase in sardine Quality Index. Belly burst was not an issue. Sardine quality could be maintained by reducing tank loading, and rapid temperature reduction using dedicated, on-board value-adding tanks. Fish should be iced between the jetty and the processing factory, and transport bins chilled using an efficient cooling medium such as flow ice.

Responses in carcass lean pH at 24 hours post-mortem in lines of Large White pigs selected for growth rate on a fixed ration over a set time

A restricted maximum likelihood analysis applied to an animal model showed no significant differences (P > 0.05) in pH value of the longissimus dorsi measured at 24 h post-mortem (pH24) between high and low lines of Large White pigs selected over 4 years for post-weaning growth rate on restricted feeding. Genetic and phenotypic correlations between pH24 and production and carcass traits were estimated using all performance testing records combined with the pH24 measurements (5.05-7.02) on slaughtered animals. The estimate of heritability for pH24 was moderate (0.29 ± 0.18). Genetic correlations between pH24 and production or carcass composition traits, except for ultrasonic backfat (UBF), were not significantly different from zero. UBF had a moderate, positive genetic correlation with pH24 (0.24 ± 0.33). These estimates of genetic correlations affirmed that selection for increased growth rate on restricted feeding is likely to result in limited changes in pH24 and pork quality since the selection does not put a high emphasis on reduced fatness.

Effects of hooking damage and hook type on post-release survival of sand flathead (Platycephalus bassensis)

This study examined post-release survival in sand flathead (Platycephalus bassensis) and whether there were survival benefits from the use of circle hooks over conventional hook patterns. Anatomical hooking location was the major factor contributing to mortality, with an almost 100% survival rate for fish hooked in the lip, mouth or eye (shallow-hooked) compared with around 64% for fish hooked in the throat or gut (deep-hooked). Mortality in deep-hooked fish was generally associated with injuries to vital organs (gills, heart, liver) and survival was significantly lower if bleeding was associated with injury (54% compared with 85% for non-bleeders). Circle hooks resulted in significantly lower deep-hooking rates (1%) compared with conventional hook types (4-9%) and, based on catch rates, were at least as effective as conventional hook patterns. Estimated survival rates for line-caught sand flathead were high, over 99% for circle hooks and between 94 and 97% for conventional hooks. These findings support the efficacy of management strategies based on size and bag limits and the practice of catch-and-release fishing for sand flathead, as well as a potential conservation benefit from the use of circle hooks.

Post capture necrosis of the feet caused by soft-catch traps – incidents, cause and prevention.

When recapturing satellite collared wild dogs that had been trapped one month previous in padded foothold traps, we noticed varying degrees of pitting on the pads of their trapped paw. Veterinary advice, based on images taken of the injuries, suggests that the necrosis was caused by vascular compromise. Five of six dingoes we recaptured had varying degrees of necrosis restricted only to the trapped foot and ranging from single 5 mm holes to 25% sections of the toe pads missing or deformed, including loss of nails. The traps used were rubber-padded, two–coiled, Victor Soft Catch #3 traps. The springs are not standard Victor springs but were Beefer springs; these modifications slightly increase trap speed and the jaw pressure on the trapped foot. Despite this modification the spring pressure is still relatively mild in comparison to conventional long spring or four-coiled wild dog traps. The five wild dogs developing necrosis were trapped in November 2006 at 5-6 months of age. Traps were checked each morning so the dogs were unlikely to have been restrained in the trap for more than 12 hours. All dogs exhibited a small degree of paw damage at capture which presented itself as a swollen paw and compression at the capture point. In contrast, eight wild dogs, 7-8 month-old, were captured two months later in February. Upon their release, on advice from a veterinarian, we massaged the trapped foot to get blood flow back in to the foot and applied a bruise treatment (Heparinoid 8.33 mg/ml) to assist restoring blood flow. These animals were subsequently recaptured several months later and showed no signs of necrosis. While post-capture foot injuries are unlikely to be an issue in conventional control programs where the animal is immediately destroyed, caution needs to be used when releasing accidentally captured domestic dogs or research animals captured in rubber-padded traps. We have demonstrated that 7-8 month old dogs can be trapped and released without any evidence of subsequent necrosis following minimal veterinary treatment. We suspect that the rubber padding on traps may increase the tourniquet effect by wrapping around the paw and recommend the evaluation of offset laminated steel jaw traps as an alternative. Offset laminated steel jaw traps have been shown to be relatively humane producing as few foot injuries as rubber-jawed traps.

Assessing the effects of line capture and barotrauma relief procedures on post-release survival of key tropical reef fish species in Australia using recreational tagging clubs.

Common coral trout, Plectropomus leopardus Lacepede, crimson snapper, Lutjanus erythropterus Bloch, saddletail snapper, Lutjanus malabaricus (Bloch & Schneider), red emperor, Lutjanus sebae (Cuvier), redthroat emperor, Lethrinus miniatus (Schneider) and grass emperor, Lethrinus laticaudis Alleyne & Macleay, were tagged to determine the effects of barotrauma relief procedures (weighted shot-line release and venting using a hollow needle) and other factors on survival. Release condition was the most significant factor affecting the subsequent recapture rate of all species. Capture depth was significant in all species apart from L. malabaricus and L. miniatus, the general trend being reduced recapture probability with increasing capture depth. Recapture rates of fish hooked in either the lip or mouth were generally significantly higher than for those hooked in the throat or gut. Statistically significant benefit from treating fish for barotrauma was found in only L. malabaricus, but the lack of any negative effects of treating fish indicated that the practices of venting and shot-lining should not be discouraged by fisheries managers for these species.

Maximising Revenue within the NT Mud Crab Fishery by Enhancing Post-Harvest Survival of Mud Crabs

Identifying the stress factors imposed on mud crab to develop stress minimisation practices for improving survival, hence increasing revenue for the industry.

Collation of health literature for tropical and exotic fruits and extracts

This report collates data on the nutrient and phytochemical content of tropical exotic fruits, the evidence for health effects from consumption of these fruit and the use of extracts from edible and non-edible parts of these plants. The knowledge of Australian fruit compared with that grown overseas is presented together with opportunities for future work by Australian researchers. Opportunities for developing commercial extracts for use as food or nutraceutical uses are also presented.

Improving avocado fruit quality and market potential by pre and post harvest factors

Improving avocado fruit quality and market potential by pre and post harvest factors.