Tomato (Lycopersicon esculentum Mill.) is an important commercial crop. High quality tomatoes for the local and export markets are grown hydroponically. In this study, the effect of electrically activated sodium bicarbonate and non-ionized sodium bicarbonate solutions on productivity and postharvest quality of hydroponically grown tomatoes was tested. Sodium bicarbonate is a ready source of bicarbonate. By using a novel technique obtained from Radical Waters (Pty) Ltd., ionized bicarbonate (anolyte) can be produced from sodium bicarbonate and applied to plants to stimulate photosynthesis, and improve yield and postharvest quality. The effect of ionized and non-ionized bicarbonate solutions on productivity and postharvest quality was studied by measuring the following: (1) Preharvest growth rate (leaf length, stem height and diameter); total yield; starch concentration in leaves; fruit count; leaf chlorophyll content; CO2-uptake; soluble solids and concentration of K+, Na+ and NO3¯ in leaves. (2) Postharvest rate of respiration and transpiration; ethylene production; total soluble solids content; ascorbic acid content; pH; fruit firmness; fruit mass; fruit diameter; longevity; concentration of K+, Na+ and NO3¯ at one-third towards maturity, two-thirds towards maturity, at maturity and during ripening, and rate of ripening at 12 and 23°C. During the preharvest period, plants treated with anolyte showed increased growth rate, starch concentration, chlorophyll content, soluble solids content and improved yield. During the growth period, the concentration of K+ and NO3¯ was higher in plants treated with anolyte than in plants treated with non-ionized sodium bicarbonate. The concentration of Na+ during the preharvest period was higher in plants treated with non-ionized sodium bicarbonate than in plants treated with anolyte. After harvest, fruits from plants treated with anolyte had a reduced rate of ethylene production, rate of respiration and transpiration, total increased soluble solids and ascorbic acid content than fruits from plants treated with non-ionized sodium bicarbonate. Fruits from plants treated with anolyte had reduced rate of ripening and were larger and heavier than fruits from plants treated with non-ionized sodium bicarbonate. Anatomical and ultrastructural studies revealed that treatment with anolyte stimulated cell growth and photosynthesis. These results were confirmed by comparing the CO2-uptake of treated and untreated plants. Application of anolyte stimulated photosynthesis, thus improving yield and fruit quality. Treatment with non-ionized sodium bicarbonate resulted in salt- stress and calcium deficiency. Some of the fruits on plants treated with non-ionized sodium bicarbonate suffered from blossom-end rot due to salt-stress. / Prof. C.S. Whitehead

No description available.

The focus of this thesis is to develop pectin-based edible films for application of fruits and vegetables to extend their post harvest shelf life. Preliminary research demonstrated that edible coatings could effectively extend the shelf life of based avocado and peach. The respiration rate, moisture loss, firmness, chemical parameters and color changed in a lower rate in coated fruits as compared with the control. Pectin-based film formulations were then evaluated to identify the proper type and concentration of pectin, lipids and plasticizers in the film. The effects of pectin, beeswax and sorbitol concentration on water vapor permeability, mechanical properties and opacity of the films were then evaluated using response surface methodology to identify appropriate levels of different components. Results of studies on film structure revealed that water vapor permeability increased by pectin and sorbitol concentration and was decreased by beeswax concentration. Mechanical properties were mainly affected by pectin and sorbitol concentration. Beeswax was the most influential factor that affected opacity which increased with increasing beeswax concentration. / In order to successfully employ these films, their adsorption behavior, thermal and thermomechanical properties were evaluated as a function of moisture content and sorbitol concentration. The adsorption behavior was strongly influenced by sorbitol concentration. Moisture content and sorbitol concentration increased the films elongation at break, but decreased tensile strength, modulus of elasticity and Tg, and increased water vapor permeability of the films. Finally, avocado was coated with a pectin-based film and the associated quality changes were evaluated during storage. From storage studies, kinetic parameters (rate constants) and activation energy were quantified to help model the quality changes in avocado quality as function of storage temperature and time. Pectin-based coating resulted in slowing down the rate of quality changes in avocado at each storage temperature. In general, most changes were well described by some form of zero or first order rate. Temperature sensitivity of rate constant was adequately described by the Arrhenius model. / A hyperspectral imaging technique was also used to gather additional tools for following quality changes associated with stored avocados. Artificial neural network (ANN) concepts were evaluated as alternated models for predicting quality changes in coated and non-coated avocados during storage at different temperature. Modeling of quality changes in avocado indicated that compared to conventional mathematical models, ANN has more feasibility to predict of these changes. Models developed for firmness, weight loss and total color difference had better fitness than respiration rate. / Finally, the effect of coating on disease severity and different properties of avocados infected by Lasiodiplodia theobromae was studied. The coated fruits demonstrated slower rate of disease progress, respiration rate, softening and color changes. Respiration rate, firmness and color parameters were sensitive to coating and disease severity, and thus these parameters could successfully used to predict fruit quality from disease in coated and uncoated avocados.

Thesis (Ph. D.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references (leaves 120-148). / Also available by subscription via World Wide Web / xv, 148 leaves, bound col. ill., col. charts 29 cm

M.Sc. / Loss of quality occurs when tomatoes are stored for more than approximately 3-5 weeks at 12 °C. The most common disorders found in tomatoes during storage are colour development to an unacceptable shade of red, softening, shrivelling due to moisture loss, loss of flavour and fungal infections. Storage life of tomatoes is generally extended by storage under refrigeration. Further, extension of shelf life can be achieved by modified atmosphere packaging (MAP). This is done by sealing actively respiring produce in polymeric film packages to modify the 0, and CO, levels within the package atmosphere. Also, 1-methylcyclopropene (1-MCP) has been proven to be an effective postharvest treatment to prolong the storage life of tomatoes. In the present study four trails were conducted. In the first trial the effects of 1-MCP dosage rate and the colour stage of harvest on the quality of `Santa' tomatoes stored for 4 weeks at 12 °C were investigated. The results indicated that ripening related changes were delayed following 1-MCP treatment. 1-MCP treated fruit were firmer, had reduced TA losses, slower colour development, and reduced physiological disorders associated with long term storage. The stage of ripeness influenced the efficacy of 1-MCP on slowing down the tomato ripening process. 1-MCP was of little benefit for fruit treated at stage 4 of ripeness. In contrast, particularly when the 1-MCP dosage was high, 1-MCP markedly delayed ripening in fruit harvested at colour stage 2 and 3, but the quality attributes such as SSC were better in treated fruits harvested at stage 3. Relatively little difference was observed between 250 and 500 nL.L -I 1-MCP and thus 500 nL.Con fruit harvested at stage 3 of ripeness was used in the remaining experiments. Effects of MAP, 1-MCP and imazalil either as combined treatments or as single treatments were studied for their effect on the quality of tomatoes. Ripening related changes were delayed and loss of weight was significantly reduced following 1-MCP treatment and MA packaging in 17 gm thickness bags. Elevated CO, in MAP after a long storage period induced anaerobic metabolism with the generation of off-odurs and the proliferation of anaerobic microbes. Selected doses of imazalil (0, 0.5, 0.05, 0.005 and 0.0005 g.L.1 ) were evaluated for their effect on the fungal infections on tomato fruits. Imazalil at a rate of 0.005 g.L"' was found to reduce fungal infections by 50% when used in combination with MAP and 1-MCP. The combination of imazalil and MAP therefore appears to be the best treatment combination to facilitate export of 'Santa' tomatoes by sea. However, with regards to reducing the loss of TA, treatment with 1-MCP would be beneficial.

Tomatoes (Lycopersicon esculentum cv. Santa) are climacteric fruit that continue to ripen after harvest. Once the fruit are separated from the plant, the physiological reactions that control the ripening process are altered, so that tomato quality is altered. The earlier the stage of ripening at harvest, the larger the discrepancy between the tomatoes left to ripen on the plant and those harvested while still unripe. Quality is lost as the tomatoes lose moisture, firmness, nutrients and stored carbohydrates. Other aspects such as colour and flavour development and cell wall modifications also affect the quality of unripe harvested tomatoes. Environmental factors that affect the postharvest quality include the temperature, humidity and atmospheric conditions in which the tomatoes are stored. Hormonal manipulation (introducing or blocking ethylene) also has an effect on the final fruit quality. This research project concentrated on the changes that occur in quality during post harvest ripening. Comparisons were made on how different post harvest treatments and storage protocols influenced the quality and longevity of tomato fruit. The purpose of this study was to determine storage conditions that would prolong the shelflife of tomatoes so that they can be acceptable for consumption for up to 40 days after harvest. The best results were obtained from tomatoes that had not completely turned red at time of harvest. These tomatoes could maintain their acceptability best when they were stored at 12°C under controlled atmosphere conditions. 1-MCP treatment was also effective in limiting quality losses for up to a week after harvest, and avoiding exposure to ethylene gas can also be recommended. Heat treatment was not at all successful in improving the longevity of the fruit. / Prof. C.S. Whitehead

Thesis (MScAgric) -- University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Postharvest berry split and abscission are prevailing physiological disorders that negatively impact on the quality of table grapes exported from South Africa. Inferior grape quality due to these disorders results in a considerable decline in consumer confidence in the branded product, which leads to a drop in demand, and consequently, lower prices. Since information concerning postharvest factors influencing postharvest berry split and abscission is limited, the search for reliable methods to adequately control these problems remains elusive. In an attempt to obtain the required information, the influence of harvest temperature, harvest maturity, perforated liners, field heat removal prior to packing, delay periods before and after packing, storage duration and the elevation of storage temperature on the development of berry split and abscission in 'Thompson Seedless' (Vitis vinifera Linnaeus) table grapes was investigated. Changes in abscission related factors during berry development, and the influence of pre-and postharvest ethylene inhibitors on the development of berry abscission in 'Waltham Cross' table grapes, was also studied. Berry split was aggravated by packing 'Thompson Seedless' grapes at high pulp temperatures of approximately 30°C, especially if the grapes were packed in non-perforated bags. The incidence of berry split could be reduced by between 80 and 90% by packing grapes in perforated instead of non-perforated liners. Perforated bags also reduced levels of S02 damage. However, due to significantly more moisture loss from grapes in perforated bags, compared to non-perforated bags, the risk of higher fruit and stem desiccation and softer berries existed. Optimum size and density of perforations needs to be determined to reduce berry split without excessive loss of moisture from the grapes, and S02gas from the air space surrounding the product. The influence of harvest temperature and liner type on berry abscission was not conclusive. Advanced maturity increased grape resistance to berry split. However, grapes harvested too mature were prone to stem desiccation and the development of Botrytis decay. The occurrence of berry abscission also appeared to increase with advanced harvest maturity. Consequently, to ensure optimal post-storage quality, 'Thompson Seedless' grapes should be harvested as soon as horticultural maturity has been reached, which appears to be at approximately 18°Brix. Field heat removal for 1.5 hours at 19°C prior to packing had no beneficial or adverse effect on berry split and abscission. Delay periods prior to packing aggravated berry abscission, but did not influence berry split significantly. Grapes delayed for 12 hours showed a significant increase in berry abscission and Botrytis decay, compared to grapes delayed for only 3 or 8 hours. Considering that the absence of fungal decay is the most important quality prerequisite in table grapes, it is of vital importance to pack grapes with as short a delay period as possible. Grapes packed in non-perforated liners and delayed for different durations after packing, before the onset of forced-air cooling (FAC), showed significant differences regarding the incidence of berry split. Grapes delayed for 18 hours had significantly higher levels of berry split directly after the delay period, compared to grapes delayed for 6 or 12 hours. No significant difference in berry abscission occurred between grapes delayed for different periods. To minimise the amount of berry split, FAC should be applied as rapidly as possible after the packing of grapes in non-perforated liners. Two storage related factors significantly influenced the incidence of berry split in 'Thompson Seedless' grapes during cold storage significantly, viz. the duration of storage at -O.soC,and the increase in temperature after low temperature storage. Berry split increased almost linearly with prolonged storage at -O.soC. An elevation of storage temperature from -O.soC to 10°C any time during the cold storage period, further aggravated the split problem. Consequently, the reduction of berry split in 'Thompson Seedless' table grapes during cold storage requires (a) the shortest possible cold storage period, and (b) good temperature management throughout distribution, from initiation of cooling until the final point of sale. The grape berry abscission potential, as quantitatively indexed by the measurement of the fruit removal force (FRF), showed significant changes during berry development of 'Waltham Cross' table grapes, from 27 to 111 days after full bloom (OAFB). This showed that at certain stages of fruit growth, 'Waltham Cross' grapes are more prone to berry abscission. At 27 OAFB, when the berries had an average diameter of 6.6mm, the grape bunches showed a significantly higher potential for berry abscission, compared to grapes sampled at a later stage. 'Waltham Cross' has inherently straggly bunches with bare shoulders. Therefore, any abscission during berry development will aggravate the problem. Consequently, it is of vital importance that any adverse factors such as moisture stress be avoided, especially during the period when 'Waltham Cross' grapes appear to be very susceptible to berry abscission. Of all parameters measured, moisture loss showed the best correlation with abscission. Grapes harvested with total soluble solids (TSS) of 12.3°Brix, 83 OAFB, had a significantly higher abscission potential than grapes harvested more mature. Therefore, by harvesting 'Waltham Cross' grapes at optimum maturity, at a TSS of approximately 16.4°Brix, berry abscission can be reduced to a great extent. It was evident that at veraison, the metabolism of grape berries changes drastically, and additional to the rapid increase in sugars and the rapid decrease in acidity, a decrease in FRF occurs. Preharvest sprays of ReTain™ (a derivative of aminoethoxyvinylglycine), which inhibits ethylene synthesis, showed no promise as a means to reduce postharvest berry abscission. A postharvest treatment with EthylBloc® (1-methylcyclopropene), which inhibits ethylene action, only reduced berry abscission during one season. / AFRIKAANSE OPSOMMING: Die fisiologiese defekte korrelbars en los korrels wat algemeen voorkom tydens opberging van sekere tafeldruif-kultivars, het 'n negatiewe invloed op tafeldruiwe wat uitgevoer word vanaf Suid-Afrika. Minderwaardige kwaliteit as gevolg van hierdie defekte het 'n aansienlike afname in verbruikers-vertroue tot gevolg wat aanleiding gee tot 'n ooreenkomstige afname in aanvraag en prys van die produk. Inligting rakende na-oes faktore wat die voorkoms van korrelbars en los korrels beïnvloed is beperk, en geen gewaarborgde metode bestaan om hierdie twee defekte volkome te beheer nie. In 'n poging om dié gewenste inligting te bekom, is ondersoek ingestel na die effek van oes-temperatuur, oes-rypheid, geperforeerde sakke, veldhitte verwydering voor verpakking, vertragingsperiodes voor en na verpakking, tydsduur van opberging, en die verhoging van die opbergingstemperatuur, op die voorkoms van korrelbars en los korrels by 'Thompson Seedless' (Vitis vinifera Linnaeus) druiwe. Daar is ook ondersoek ingestel na veranderings in afsnoering verwante faktore tydens korrel-ontwikkeling, en die invloed van vooren na-oes toedienings van etileen inhibeerders op die ontwikkeling van los korrels by 'Waltham Cross'tafeldruiwe. Korrelbars is vererger deur 'Thompson Seedless' met hoë pulptemperature van ongeveer 29.5°C te verpak, veral indien dit in 'n riie-geperforeerde sak verpak is. Die voorkoms van korrelbars kon tussen 80 en 90% verminder word deur 'Thompson Seedless' druiwe in geperforeerde sakke te verpak, in plaas van nie-geperforeerde sakke. Geperforeerde sakke het ook S02 skade op die druiwe verminder. Tog, as gevolg van betekenisvol meer vogverlies vanaf druiwe in geperforeerde sakke as vanaf druiwe in nie-geperforeerde sakke, bestaan die risiko van meer stingel-uitdroging en minder ferm korrels indien druiwe in geperforeerde sakke verpak word. Optimale grootte en digtheid van perforasies moet bepaal word om korrelbars te verminder, maar sonder oormatige vogverlies vanaf die druiwe en oormatige verlies aan S02. Die invloed van oes-temperatuur en sak-tipe op los korrels was nie oortuigend nie. Gevorderde oes-rypheid het die druif se weerstand teen korrelbars verhoog. Daarteenoor was druiwe wat té ryp geoes is, meer gevoelig vir stingel-uitdroging en Botrytis bederf. Dit wilook voorkom of die voorkoms van los korrels toeneem met gevorderde rypheid. Dus, om optimum kwaliteit na opberging te verseker, moet 'Thompson Seedless' geoes word sodra hortologiese rypheid bereik word, wat blyk om by 'n totale opgeloste vaste stof-inhoud (TOVS) van ongeveer 18°Brix te wees. Veldhitte verwydering voor verpakking, vir 1.5 uur by 19°C, het geen effek gehad op die voorkoms van korrelbars en los korrels nie. 'n Vertragingsperiode voor verpakking het die los korrel-probleem vererger, alhoewel dit geen betekenisvolle invloed op die voorkoms van korrelbars gehad het nie. Druiwe wat vir 12 uur voor verpakking vertraag is, het betekenisvol meer los korrels en Botrytis bederf getoon, in vergelyking met druiwe wat slegs 'n vertragingsperiode van 3 of 8 uur ondergaan het. Aangesien die afwesigheid van bederf die belangrikste kwaliteits-vereiste vir tafeldruiwe is, is dit van kardinale belang om druiwe so gou as moontlik na oes te verpak. Druiwe, verpak in nie-geperforeerde sakke, wat vir verskillende periodes vertraag is voor geforseerde-lug verkoeling, het betekenisvolle verskille getoon betreffende die voorkoms van korrelbars. Druiwe vertraag vir 18 ure voor verkoeling, het betekenisvol meer korrelbars getoon, soos gemeet onmiddellik na die vertragingsperiode, in vergelyking met druiwe wat slegs vir 6 of 12 ure vertraag was. Geen betekenisvolle verskille in los korrels het voorgekom tussen druiwe wat verskillende vertragingsperiodes ondergaan het nie. Om korrelbars te verminder, moet geforseerde-lug verkoeling so gou as moontlik na verpakking van druiwe in nie-geperforeerde sakke toegepas word. Twee opbergings-verwante faktore beïnvloed die voorkoms van korrelbars by 'Thompson Seedless' druiwe tydens koelopberging, naamlik die tydsduur van opberging by -O.soC,asook 'n styging in temperatuur vanaf -O.soC tot 1DoC. Korrelbars het feitlik liniêr toegeneem met verlengde opberging by -O.soC. 'n Styging in temperatuur vanaf -O.SoCtot 1DoCop enige tydstip gedurende die koelopbergingsperiode, het korrelbars verder vererger. Dus, om korrelbars by 'Thompson Seedless' tydens opberging tot die minimum te beperk, moet die tydsduur van opberging so kort as moontlik wees, en moet die koue ketting regdeur die distribusie-proses gehandhaaf word, vanaf inisiëring van verkoeling tot en met die uiteindelike verkoop van die produk. Die afsnoerings-potensiaal van druiwe, soos kwantitatief geïndekseer is deur meting van die vrug-verwyderings-vermoë (VVV), het betekenisvol verander gedurende korrel-ontwikkeling van 'Waltham Cross' tafeldruiwe, vanaf 27 tot 111 dae na volblom (DNVB). Dit het getoon dat 'Waltham Cross' druiwe by sekere stadiums van vrug-groei meer gevoelig is vir korrel afsnoering. By 27 DNVB, wanneer die korrels 'n gemiddelde deursnee van 6.6mm gehad het, het die druiwe 'n betekenisvolle hoër potensiaal vir afsnoering getoon, in vergelyking met druiwe wat op 'n latere stadium getoets is. 'Waltham Cross' is inherent geneig tot yl trosse met kaal skouers, gevolglik sal enige afsnoering tydens korrel-ontwikkeling die probleem vererger. Dus is dit van kardinale belang dat enige nadelige faktor, soos byvoorbeeld vogstres, vermy moet word, veral gedurende periodes wanneer dit wil voorkom of 'Waltham Cross' baie vatbaar is vir korrel afsnoering. Van al die parameters wat gemeet is, het vogverlies die beste korrelasie met korrel afsnoering getoon. Druiwe wat 83 DNVB, by 'n TOVS van 12.3°Brix geoes is, het 'n betekenisvol hoër potensiaal vir korrel afsnoering getoon, in vergelyking met druiwe wat ryper geoes is. Dus, deur 'Waltham Cross' druiwe by optimum rypheid te oes, by 'n TOVS van ongeveer 16.4°Brix, kan korrelbars in 'n groot mate verminder word. Tydens verelson, wanneer die metabolisme van die druiwe drasties verander, was daar gepaardgaande met die drastiese toename in TOVS en die drastiese afname in totale titreerbare sure (TSS), ook 'n afname in Voor-oes bespuitings met ReTain™, wat etileen sintese inhibeer, het geen potensiaal getoon om los korrels by 'Waltham Cross' te verminder nie. 'n Na-oes behandeling met EthyIBloc®, wat etileen werking inhibeer, het slegs korrel afsnoering in een van die seisoene effens verminder.

Choi Yin Yee. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 164-187). / Abstracts in English and Chinese. / List of Abbreviations / List of Tables / List of Figures / Chapter Chapter 1: --- "Background of straw mushroom, Volvariella volvacea" / Chapter 1.1 --- History and economic value of straw mushroom --- p.1 / Chapter 1.2 --- Nutritional value and medical use of straw mushroom --- p.2 / Chapter 1.3 --- Cultivation of straw mushroom --- p.3 / Chapter 1.4 --- Life cycle and developmental stages of straw mushroom --- p.5 / Chapter 1.5 --- Objectives of the research --- p.6 / Chapter Chapter 2: --- Determination of straw mushroom quality during postharvest storage / Chapter 2.1 --- Introduction --- p.18 / Chapter 2.2 --- Materials and methods / Chapter 2.2.1 --- Determination of surface color changes --- p.19 / Chapter 2.2.2 --- Determination of weight loss and dry weight --- p.19 / Chapter 2.2.3 --- Examination of mushroom surface structure --- p.20 / Chapter 2.2.4 --- Statistical analysis --- p.20 / Chapter 2.3 --- Results and discussion / Chapter 2.3.1 --- Browning during postharvest storage --- p.20 / Chapter 2.3.2 --- Weight loss and dry weight changes during storage --- p.22 / Chapter 2.3.3 --- Surface structural changes during postharvest storage --- p.23 / Chapter Chapter 3: --- Physiological studies of straw mushroom during postharvest storage / Chapter 3.1 --- Introduction --- p.31 / Chapter 3.2 --- Materials and methods / Chapter 3.2.1 --- Materials --- p.33 / Chapter 3.2.2 --- Respiration rates of different produce --- p.34 / Chapter 3.2.3 --- Changes of respiration rate and detection of ethylene production in straw mushroom --- p.34 / Chapter 3.2.4 --- Exogenous ethylene treatment --- p.34 / Chapter 3.3 --- Results and discussion / Chapter 3.3.1 --- Comparative studies of respiration rates between different fresh produce --- p.35 / Chapter 3.3.2 --- Ethylene production and effect of exogenous ethylene effect on straw mushroom --- p.36 / Chapter 3.3.3 --- Change in respiration during postharvest storage --- p.37 / Chapter Chapter 4: --- Biochemical studies of straw mushroom during postharvest storage / Chapter 4.1 --- Introduction / Chapter 4.1.1 --- Hydro lytic enzymes / Chapter 4.1.1.1 --- Protease --- p.43 / Chapter 4.1.1.2 --- Lipase --- p.44 / Chapter 4.1.1.3 --- Chitinase --- p.46 / Chapter 4.1.2 --- Enzymatic browning / Chapter 4.1.2.1 --- Background --- p.48 / Chapter 4.1.2.2 --- Action of polyphenol oxidase --- p.49 / Chapter 4.1.2.3 --- Control of enzymatic browning --- p.50 / Chapter 4.2 --- Materials and methods / Chapter 4.2.1 --- Source --- p.52 / Chapter 4.2.2 --- Enzyme extraction --- p.52 / Chapter 4.2.3 --- Soluble protein determination --- p.52 / Chapter 4.2.4 --- Protease assay --- p.53 / Chapter 4.2.5 --- Lipase assay --- p.53 / Chapter 4.2.6 --- Chitinase assay --- p.54 / Chapter 4.2.7 --- PPO assay --- p.54 / Chapter 4.2.8 --- Optimal pH determination and substrate specificity of PPO --- p.55 / Chapter 4.2.9 --- PPO inhibitors studies --- p.56 / Chapter 4.2.10 --- Localization of PPO in the fruit body of straw mushroom --- p.56 / Chapter 4.3 --- Results and discussion / Chapter 4.3.1 --- Protease activity during postharvest storage --- p.57 / Chapter 4.3.2 --- Lipase activity during postharvest storage --- p.58 / Chapter 4.3.3 --- Chitinase activity during postharvest storage --- p.59 / Chapter 4.3.4 --- pH optimum and substrate specificity of PPO --- p.61 / Chapter 4.3.5 --- PPO activity during postharvest storage --- p.62 / Chapter 4.3.6 --- Effect of various inhibitors on PPO activity --- p.63 / Chapter 4.3.7 --- Localization of PPO in the fruit body of straw mushroom --- p.64 / Chapter Chapter 5: --- Microorganisms in the fruit body of straw mushroom during postharvest storage / Chapter 5.1 --- Introduction --- p.81 / Chapter 5.2 --- Materials and methods / Chapter 5.2.1 --- Evaluation of bacterial population --- p.85 / Chapter 5.2.2 --- Isolation of bacteria --- p.85 / Chapter 5.2.3 --- Treatment of antibacterial agents --- p.87 / Chapter 5.2.4 --- Effect of moisture on bacterial population --- p.87 / Chapter 5.2.5 --- Statistical analysis --- p.87 / Chapter 5.3 --- Results and discussion / Chapter 5.3.1 --- Bacterial population during postharvest storage --- p.88 / Chapter 5.3.2 --- Bacteria growth and mushroom deterioration --- p.89 / Chapter 5.3.3 --- Identification of bacteria isolated from straw mushroom --- p.92 / Chapter 5.3.4 --- Relationship between moisture and bacterial population --- p.95 / Chapter Chapter 6: --- Preservative studies of straw mushroom / Chapter 6.1 --- Introduction --- p.107 / Chapter 6.1.1 --- Chemicals treatment in produce --- p.109 / Chapter 6.1.1.1 --- Application of browning inhibitors --- p.110 / Chapter 6.1.1.2 --- Role of calcium in preservation --- p.111 / Chapter 6.1.2 --- Modified atmosphere technology --- p.114 / Chapter 6.2 --- Materials and methods / Chapter 6.2.1 --- Dipping experiment with browning inhibitors --- p.117 / Chapter 6.2.2 --- Application CaCl2 in straw mushroom cultivation --- p.117 / Chapter 6.2.3 --- Postharvest storage of straw mushroom under modified atmosphere --- p.118 / Chapter 6.2.4 --- Statistical analysis --- p.119 / Chapter 6.3 --- Results and discussion / Chapter 6.3.1 --- Effect of browning inhibitors on mushroom quality --- p.119 / Chapter 6.3.2 --- Effect of calcium chloride on mushroom quality --- p.121 / Chapter 6.3.3 --- Effect of modified atmosphere on mushroom quality --- p.124 / Chapter Chapter 7: --- Conclusion --- p.159 / References --- p.164

Includes bibliographical references (leaves 174-201) / xxii, 201, [20] leaves : ill., photos (col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, School of Agriculture and Wine, Discipline of Wine and Horticulture, 2004

Simple technologies are required for reducing the post harvest losses of horticultural produce. Edible films are being studied extensively for application on fresh and cut fruits and vegetables. Tomato, being a very nutritious and important food and a highly perishable climacteric fruit, this study was planned to investigate the application of chitosan films. Chitosan is a biodegradable waste product from sea food and is safe for consumption. With a view to broaden its antimicrobial activity it was combined with lysozyme, a lytic enzyme. Since the edible films are sensitive to changes in temperature and humidity, they were studied under ambient and optimal conditions of storage. / This study showed that 1% chitosan was more suitable for tomatoes for storage at both conditions of ambient and low temperature. Respiration study showed that 1% chitosan treatments resulted in more favorable levels of CO 2 production and internal O2. This was reflected in the quality of tomatoes held under these conditions. Two per cent chitosan films were unsuitable due to their high CO2 production and low internal O 2 levels. Spoilage was more apparent in this treatment. Lysozyme addition did not show any additional benefit. / The research in this study has demonstrated that the selection of edible films for horticultural produce needs to be integrated with the requirement of storage conditions of the produce.