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Item Exploration of fruit parameters for non-destructive identification of calyx cavity in ‘Fuyu’ persimmon (Diospyros kaki L.)(Informa UK Limited, trading as Taylor & Francis Group, 2024-05-08) Longuet-Higgins JM; Rivera SA; Woolf AB; Li M; Golding JCalyx cavity is a common physiological disorder in many persimmon cultivars. It is characterised by a separation between the calyx and the surrounding flesh. The presence of calyx cavity in export fruit can lead to phytosanitary risks and reduced storage potential due to more rapid softening and increased chilling injury. Manual detection of calyx cavity at packing is very time-consuming and uneconomic. This work investigated the ability of non-destructive evaluation, combined with modelling, to identify calyx cavity in ‘Fuyu’ persimmons. Fruit were evaluated at harvest, followed by a period of nine-week storage in modified atmosphere packaging at 0°C. The presence and severity of calyx cavity was related with higher red colouration and fresh weight before storage. Using colour index data and weight data, binary classification of calyx cavity by linear discriminant analysis (LDA) resulted 74.1% correct segregation. The model correctly identified 70.5% of calyx cavity fruit (29.5% false negatives) and 77.4% of no cavity fruit (22.6% false positives). The use of non-destructive calyx cavity classification based on the evaluation of quality parameters is a starting point in providing the ability to segregate healthy fruit before packaging and storage. Further work is necessary to improve model performance before implementation is viable.Item Genetic metabolite and phenotypic determination of friction discolouration in pear : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, New Zealand(Massey University, 2015) Saeed, MunazzaFriction discolouration (FD) of pears is a postharvest disorder responsible for significant consumer discontent in markets because of the unattractive appearance of the fruit surface. New Zealand pear breeders are aiming to develop novel pear varieties with consumer desired fruit characters (skin colour, flavour and storability), with reduced susceptibility to FD. Therefore understanding the genetic control of FD is essential to enable development of new pear cultivars using genomics-informed breeding. FD is influenced by agronomic and genetic factors. Previous research on this disorder has been limited to a small number of commercial cultivars and no study has been done to understand its genetic basis. Biochemical constituents (polyphenol oxidase activity, phenolic compounds and ascorbic acid concentration) and skin anatomy have been proposed to play important roles on FD susceptibility in a limited number of cultivars. The Plant and Food Research (PFR) breeding population with hundreds of closely related seedlings is an ideal resource to test whether these previously identified associations hold true across multiple genotypes. In this study, 241 genotypes from two segregating populations (POP369 and POP356) derived from interspecific crosses between Asian (Pyrus pyrifolia Nakai and P. bretschneideri Rehd.) and European (P. communis) pears were used to identify biochemical and genetic factors associated with susceptibility to FD. In 2013, a small replicated trial involving eight genotypes was conducted. Large variability for FD and other variables was recorded. Four different trends were observed for genotypes for which multiple harvests were obtained in a single season. Most of the genotypes were consistently low or consistently high throughout the season, but a proportion (26.1 %) showed an increase in FD susceptibility during the season and a further 15.7 % showed a decreasing trend in susceptibility. Twenty genotypes had multiple harvests in each of 2011 and 2012, and 13 of these showed consistent trends from year to year. These results indicate a significant genetic component to FD but with additional influence from the stage of fruit maturity at harvest and external environmental conditions. Single nucleotide polymorphism (SNP)-based linkage maps suitable for QTL analysis were developed for the parents of both populations. The maps for population POP369 comprised 174 and 265 SNP markers for the male and female parent, respectively, while POP356 maps comprised 353 and 398 SNP markers for the male and female parent, respectively. Phenotypic data for 22 variables measured over two successive years (2011 and 2012) were used for quantitative trait locus (QTL) analysis. QTLs linked to phenotyped variables were identified, including QTLs for FD on linkage groups 2, 3, 7, 10 and 14. A number of stable QTLs across the years were detected for some aspects of fruit quality as well as potential risk factors for FD incidence. Overall, no single underlying phenotypic variable (enzyme or substrate) appeared to act as a rate limiting factor to susceptibility of FD in both populations and in 2013 trial. However certain phenolics consistently appeared to have weak negative association with FD. This suggests a separate role from their typical concept of being a substrate. Identification of stable QTLs controlling firmness, PPO activity, and phenolic compound concentration have also provided future opportunities for identification of candidate genes by utilizing the reference genome sequences of ‘Bartlett’ and ‘Dangshansuli’ pears and syntenic apple ‘Golden Delicious’. This study also demonstrated that FD is controlled by multiple small effect QTLs and genomic selection could be employed to select elite genotypes with reduced susceptibility to FD, early in the breeding cycle.Item Role of calcium and mechanical damage in the development of localised premature softening in coolstored kiwifruit : a dissertation presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science at Massey University(Massey University, 1997) Davie, Ivan JohnPreharvest, harvest, and postharvest factor(s) were examined to identify the causes of premature quality loss during long term coolstorage of kiwifruit (Actinidia deliciosa). Investigation centred around the role of mechanical damage and calcium in the development of softening disorders, including soft patches (localised soft areas on fruit surface), premature softening, and low temperature breakdown (LTB) during storage. Kiwifruit were vulnerable to compression and impact from harvest onwards, with damage usually being expressed after a period of coolstorage. Physical damage normally just affected the fruit tissue in direct contact with the applied force. Impact damage, and to a lesser extent compression damage, depended on the size of the force and firmness of fruit when damaged. As kiwifruit softened, their susceptibility to soft patch development as a result of physical damage increased whereas the likelihood of flesh fracture in response to impact declined. These changes are attributed to the change in nature of the flesh, which is 'brittle' at harvest and 'viscoelastic' after softening. Physical damage to coolstored kiwifruit caused a slight drop in final firmness whereas there was no effect on firmness if it occurred at harvest. Fruit with softening disorders consistently had lower calcium contents (about 12% less) than equivalent healthy fruit. Fruit with soft patches had a high phosphate content, low dry matter, and at harvest, a low soluble solids content. A causative role for calcium in soft patch development was demonstrated by preharvest calcium treatments that elevated calcium content of the harvested fruit. Other orchard factor(s) were probably the cause of a weaker relationship between calcium content at harvest and storage behaviour of fruit. Although firmness at harvest declined with later picking, after coolstorage, fruit harvested more mature had a higher firmness and lower incidence of LTB. Symptoms for LTB were consistent with chilling injury whereas soft patches appeared to be due to localised premature senescence and not low temperature. A conceptual model of key factor(s) which cause the initiation and development of softening disorders in kiwifruit is proposed. Implications of this model for further investigation of these phenomena and for commercial handling of fruit are discussed. Further development of this model to produce a predictive model of fruit storage potential would require further characterisation of other important influences in storage behaviourItem Fresh and processed apple products : vacuum infiltration, texture and quality : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science at Massey University(Massey University, 1997) Newman, Suzie Marie; Newman, Suzie MarieApple slice texture and quality is affected by a diverse array of preharvest, postharvest and processing factors. The study described in this thesis had two primary objectives: 1) to investigate factors that influence the effectiveness of the vacuum infiltration process and thereby identify ways to enhance infiltration in difficult-to-infiltrate fruit. 2) to ascertain the effects of a range of pre- and post- harvest factors including cultivar, temperature, edible surface coatings and calcium treatments on fresh and processed apple texture and quality. Vacuum infiltration is used to replace the 8-36% of tissue volume made up by occluded gases in the commercial production of solid-pack canned apple slices. This removal: reduces textural degradation caused by thermal expansion of these gases; prevents can corrosion and off-flavour development caused by residual oxygen; and ensures that relative density of the tissue is increased sufficiently to achieve prescribed can fill weights. Vacuum infiltration is often incomplete for fruit produced in cold growing seasons and also with immature fruit. In this study, level of infiltration achieved in apple slices was affected by pre-condition of the tissue (eg. maturity, porosity, whole fruit density) and by variables that relate directly to the vacuum infiltration process (eg. vacuum time, absorption time, solution temperature). Infiltration was enhanced in fruit taken from later harvests and in fruit pre-stored for a short period at 20 °C. Key aspects of the vacuum infiltration process were investigated and the relationships between vacuum time, absorption time, and slice relative density were characterised. Reduced vacuum levels were detrimental to liquid impregnation. To maximise infiltration in 'Braeburn' fruit required: high vacuum levels (preferably > 95 kPa), vacuum times of approx 2 min, and absorption times > 6 min. Infiltration was enhanced by heating the infiltrating solution. The texture and quality of solid-pack canned apple slices is to a large extent determined by the quality of the raw product. 'Braeburn', 'Fuji' and 'Granny Smith' apples varied quite markedly in terms of textural quality, storage potential, tolerance of ambient temperatures and ultimately in their response to processing. In general, fresh and processed apple texture declined with increasing fresh fruit storage temperature and duration. Application of edible surface coatings enhanced texture and reduced free-juice content of canned slices. The level of benefit achieved varied considerably with cultivar and storage temperature and, to a more limited extent, grower line and coating concentration. Calcium application during the pre- or post-harvest phases had little effect on processed slice texture, but in some cases free-juice volume was reduced. The interrelationships between the variables under study are discussed and a conceptual model presented that describes the effects of key postharvest variables on fresh and processed fruit texture.Item Studies of the factors affecting the yield and quality of single truss tomatoes : a thesis presented in partial fulfilment of the requirements for the degree of Doctorate of Philosophy in Horticultural Science at Massey University(Massey University, 1996) Morgan, Lynette StellaThis research was conducted to evaluate the potential of the single truss system of tomato production to produce high yields of quality fruit under New Zealand conditions. The NFT hydroponic system was used to grow the plants so that nutrient solution conductivity could be maintained close to predetermined levels. In the first experiment three cultivars were compared. At the time of fruit set of the first truss four conductivity treatments (2, 4, 6 and 8 mS cm-1) were applied. Yield and fruit quality data was obtained from each of six crops over an 18 month period. Yield (fruit size) decreased with increasing conductivity for all three cultivars. Season also had a significant effect on yield, with an April harvested crop having the highest yield. Both fruit brix and titratable acidity were increased at the higher conductivity levels. There were also cultivar and seasonal differences in fruit quality, with the cherry cultivar 'Cherita' consistently producing the highest brix and titratable acidity levels. Brix levels were found to be low in the December harvested crop, while acidity was highest in the December, April and July harvested crops. Season, solution conductivity and cultivar influenced plant leaf area and leaf area index. Solution conductivity also effected foliar mineral levels, as did cultivar. Three successive multi truss crops were grown in a pumice media system to provide fruit quality data for sensory evaluation and comparison with single truss and commercial compositional fruit quality. The same three cultivars as were compared in the single truss crop experiment were grown at three conductivity levels (2, 4 and 6 mS cm-1) applied at the time of fruit set of the first truss. Fruit samples were taken from the 5th and 6th trusses for quality evaluation. Season and solution conductivity had an effect on fruit dry matter percentage and brix. Fruit shelf life was affected by season, conductivity and cultivar, with a longer shelf life obtained from fruit grown at the higher conductivity levels. The December harvested crop had the lowest overall shelf life. Fruit firmness was only affected by solution conductivity, with the fruit from the higher conductivity treatments being firmest. Sensory evaluation of Rondello fruit on three separate occasions showed that the higher conductivity treatment scored highest for most attributes, and that these sensory scores correlated well with brix and titratable acidity levels. A second single truss crop experiment focused on manipulation of the source/sink relationship (fruit and leaf number combinations) of three successional crops and the effect of spring and winter CO2 enrichment on two of the three crops. The summer crop also evaluated the effect of crop shading and source/sink relationship on fruit yield, as high fruit temperatures were suspected to have reduced yield in the previous summer single truss crops. Yield and fruit quality data was collected from all three crops, along with fruit and environmental temperature recordings from the summer crop. It was found that season and fruit number effected yield, with the 8 fruit per plant treatment resulting in the greatest yield. Leaf number (either 2 or 3) and season affected fruit dry matter percentage, brix and leaf area, while fruit number influenced brix levels. CO2 enrichment (1000 ppm) had no effect on either spring or winter fruit yield, but did advance crop maturity allowing an extra crop per year to be produced. Thus yearly yield was increased by CO2 enrichment. CO2 enrichment improved fruit quality in the spring crop, but had no effect on the winter crop. Shading of the summer crop resulted in an increase of 10% in total fruit yield and 19% in marketable fruit yield, due to the presence of smaller fruit and heat induced ripening disorders in the unshaded crop. Both leaf number and shading treatments affected titratable acidity, with unshaded fruit having greater percent citric acid levels. Shelf life and fruit firmness was greater in the shaded crop. Air, canopy and fruit temperatures were reduced under shade, with exposed fruit often reaching extreme temperatures (above 40°C). Having established that leaf and fruit temperatures were reaching extreme levels during the summer in a single truss cropping situation, the effect of these temperatures on photosynthesis and fruit respiration was examined. The effect of leaf age on photosynthesis was also examined as single truss plants do not continue to produce young foliage to maintain photosynthesis levels. After harvest, net photosynthesis and the light compensation point, which had been increasing began to fall rapidly at all light levels. It was found that after an initial drop as leaves matured, leaf age did not effect net photosynthesis. Plants exposed to 800 PAR showed maximum net photosynthesis at temperatures between 25 – 27°C. Net photosynthesis ceased at 43°C. Fruit truss respiration rates were determined at 4 temperatures (25, 30, 35 and 40°C), on 3 occasions (18, 26, 36 and 40 days after fruit set). 5 different tissue sample combinations were assessed comprising, the whole truss with sealed and unsealed cut surfaces, fruit only with sealed and unsealed calyx scar and calyx, peduncles and plant stem only. It was found that temperature, truss portion assessed and stage of fruit maturity all affect fruit respiration rate, with the fruit only (calyx scar unsealed) resulting in the greatest CO2 efflux. It was concluded that while the fruit epidermis is relatively impermeable to gas escape, the main route for Co2 is through the calyx scar. Mature green fruit had the greatest response of increased CO2 production with increasing temperature, while temperatures above 25°C disrupted the climacteric pattern of CO2 evolution. It was concluded that in single truss plants, when temperatures were above 30°C, net photosynthesis is reduced, while fruit respiration begins to increase rapidly, both responses having a detrimental effect on yield. The single truss system was shown to produce yields and fruit quality equal to those of good multi truss commercial tomato producers in New Zealand. This was achieved by CO2 enrichment for crop advancement and summer crop shading, while moderate levels of solution conductivity produced good quality fruit. However, there is the possibility of further improving these yields by utilisation of other technologies such as a movable bench system and manipulation of plant density, timing of conductivity application, and different cultivars. The potential of this system for high quality, high yielding tomato fruit production warrants commercial evaluation.Item Mathematical modelling of modified atmosphere packaging systems for apples : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Process and Environmental Technology at Massey University(Massey University, 1996) Merts, Ingeborg; Merts, IngeborgENZA New Zealand (International) is considering the use of modified atmosphere packaging (MAP) as an adjunct to cool storage for cartons of apples. The objectives of this study were to measure modified atmosphere development in apple cartons and to develop a mathematical model that could be used as a tool for package design and optimization. Storage trials were carried out with film-lined cartons of 'Braeburn', 'Royal Gala', and 'Granny Smith' apples. Measured package O2 and CO2 concentrations showed excellent reproducibility for cartons with heat-sealed liners. Liners closed by folding produced less modified and less consistent package atmospheres, especially for thicker films (40 µm versus 25 µm). Macroscopic holes in the liners resulted in almost total loss of atmosphere modification, whereas microscopic holes resulted in smaller changes apparent for O2 concentrations only. A high incidence of film damage could quickly erode any potential fruit quality benefits imparted by the liners. Packing of warm rather than pre-cooled fruit resulted in much faster rates of atmosphere modification, without the development of unduly low O2 or high CO2 concentrations. The detrimental quality effects of slower cooling rates for film-lined cartons may outweigh any benefits of more rapid modified atmosphere development. Short-term exposures (less than 24 hours) to 20°C resulted in relatively short-lived and non-critical disturbances to package atmospheres. Periods of more than 3 days at 20°C led to a significant risk of anaerobic conditions or harmful CO2 levels forming within the fruit, especially within the 40 µm liners. Folding rather than heat-sealing of liners did not reduce this risk. The MAP model simulated fruit respiration as a function of temperature and fruit O2 and CO2 concentrations; O2, CO2, N2, and water vapour exchange between the fruit, package, and external atmospheres; condensation of moisture within the package; and moisture sorption by paper-based packaging materials. Gas concentrations and temperature throughout (i) the fruit and (ii) the package atmosphere were each assumed to be uniform with position. The model can be applied to a wide range of packages under variable-temperature storage regimes. The model closely predicted observed trends in experimental data collected during the MA storage trials, but tended to under-predict CO2 concentrations and performed less well under conditions of extremely modified atmospheres. Sensitivity analyses showed that this lack of fit was not greater than that which could be explained by uncertainties in respiration and permeability data. It is recommended that future work be aimed at resolving the worst of these uncertainties before a significant amount of effort is directed towards further model development. The MAP model was considered sufficiently accurate for it to be usefully applied to the design and optimization of MAP systems.Item Gas exchange, ripening behaviour and postharvest quality of coated pears : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Postharvest Physiology and Technology at Massey University, New Zealand(Massey University, 1998) Amarante, Cassandro Vidal Talamini do; Amarante, Cassandro Vidal Talamini doPear cultivars 'Bartlett', 'Beurre Bosc', 'Doyenne du Comice', and 'Packham's Triumph' were treated with different levels of deposits of a carnauba based wax on the skin and assessed for gas exchange, ripening behaviour and postharvest quality. The response to coating treatments was strongly dependent on cultivar, ripening stage and environmental temperature. 'Bartlett', 'Comice' and 'Packham's', with non-lignified skin, had substantial reductions in skin permeance (P'j) with small increases in coating deposit. Magnitudes of reduction in P'j to different gases were observed in the order: P'O2 > P'CO2>> P'H2O. The skin of 'Bosc', with lignified cells, had high P'H2O and low P'CO2' and increasing the amount of coating deposited on the skin resulted in small reductions of P'H2O and a gradual reduction of P'O2 and P'CO2. 'Bartlett' and 'Bosc' had a high risk of developing internal disorders caused by excessive internal accumulation of CO2 at low temperatures when treated with substantial coating deposits, as a result of high respiration rate ('Bartlett') or low P'CO2 of coated skin ('Bosc'). These cultivars were also less tolerant to hypoxia (expressed in terms of internal lower O2 limit, LOLi) created by high coating concentrations, and their level of tolerance reduced with increasing ripeness. 'Comice' and 'Packham's' were highly tolerant of hypoxia [the fruit did not ferment despite of an internal O2 partial pressure (piO2)@ 0 kPa]. Respiration rates, softening and colour change followed a Michaelis-Menten model when plotted against piO2, while internal CO2 partial pressure (piCO2) had virtually no explanatory power for these variables during shelf life. Variable cover of skin pores in cultivars having high P'j might result in variable P'O2 and, consequently, variable piO2. This could increase the naturally high ripening variability of pears treated with a given coating concentration. Softening had a lower Michaelis-Menten constant for pio2 than skin colour. Therefore, coated pears with intermediary pio2 might have variable postharvest quality mainly in terms of colour change, and the fruit may still soften while being unable to change in colour. For 'Comice', higher levels of coating deposit resulted in more substantial modification of internal atmosphere during cold storage, slightly increasing ripening delay. These treatments reduced wastage by diminishing the incidence of senescent breakdown and senescent scald after long term storage and by reducing skin friction discolouration during shelf life. Increasing the amount of coating deposit improved skin gloss and reduced senescent breakdown of 'Bartlett', 'Comice' and 'Packham's' during shelf life. The results show that optimisation of surface coatings should take into account differences between cultivars, ripening stage when the fruit is coated and storage temperature to avoid the risk of fermentation and physiological disorders. Even though there are some quality problems due to uneven ripening, wax coatings represent a technology with high potential for the pear industry, improving the finish of the skin, reducing water loss, delaying ripening and reducing the incidence of senescence related disorders.Item Factors affecting mass loss of apples : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science at Massey University, New Zealand(Massey University, 1998) Maguire, Kate Marie; Maguire, Kate MarieMass loss from harvested apples causes direct loss in returns to growers and marketers of fruit. This thesis characterises the process of mass loss in harvested apples, exploring the effects of various factors on water vapour permeance of the fruit, a measure of the ease with which water escapes from the fruit. Values of permeance of 'Braeburn' and 'Pacific Rose'TM apples were roughly twice those of 'Cripps Pink' and 'Granny Smith'. Permeance of 'Braeburn' and Pacific Rose'TM apples increased with later harvest date whilst values for 'Cripps Pink' and 'Granny Smith' remained relatively constant. There were small differences in mean permeance of apples from different regions. Some growers produced more fruit with high water vapour permeances than others. There was no relationship between maturity indicators tested and the water vapour permeance of the fruit. Fruit from the inner regions of trees and with high numbers of fruit in contact had high permeances. Variation in water vapour permeance around the surface of the fruit had no pattern with respect to blush or sun/shade sides, nor was there any relationship with cuticular thickness. Rather, variation in water vapour permeance of fruit was linked to the extent of cuticular micro-cracking. A model was developed which explains the water vapour permeance based on the proportion of fruit surface which is cracked. Artificial stretch applied to pieces of fruit skin increased cracking and permeance. Strain in the cuticle during growth and development of the fruit created a reticulate crack network. Micro-cracking could be important in determining susceptibility to mass loss and shrivel after harvest. Permeance of 'Braeburn' apples decreased after harvest; the extent of this decrease was greater for low relative humidity and high temperature and for fruit with high initial levels of micro-cracking. Bruising caused by impact damage on 'Braeburn' apples increased water vapour permeance of fruit only very slightly. A conceptual model is presented which summarises relationships between fruit attributes, environmental conditions and processes which contribute to overall mass loss of apples. A composite mathematical model from previous models developed in the thesis is presented which describes total water loss as determined by the level of micro-cracking in the fruit cuticle, time after harvest, relative humidity and temperature of the storage environment. A number of suggestions for minimised mass loss in the apple industry are presented based on three strategies: minimisation of permeance, reduction of driving force for water loss and segregation of lines of high risk and applying appropriate handling regimes. The composite model could be used to explore a range of alternative handling and marketing scenarios in terms of total mass loss.Item Enhancement of aroma volatile compounds in apples : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Science at Massey University(Massey University, 1997) Wirut, Ampun; Ampun, WirutApple aroma is a complex of volatile compounds produced by fruit. It is one of the most important quality factors giving a characteristic flavour to fruit and its products. The present study investigated the effect of short-term hypoxic concentrations and duration of CO2 and/or N2 treatments at 20°C on changes in production of important aroma volatile compounds after treatment during shelf-life conditions at 20°C and 70% RH, in some commercial apple cultivars at harvest and following storage in air or controlled-atmospheres (CA). Different methods of extracting and analysing aroma volatiles from apples were compared in order to optimise a process for subsequent experiments. Juice from homogenised apple fruit could be held in an ice bath for up to 60 minutes after homogenisation without loss of major volatile compounds. Octyl acetate concentrations between 50 and 5000 ppm in the final concentrated sample was a suitable internal standard for GLC analysis; as an external standard, a mixture of authentic volatile compounds of known concentration provided accurate quantification of aroma volatiles from juice samples. Volatiles were obtained from apple juice either by a dynamic headspace (purge and trap) technique using a Tenax® trap or by direct extraction with a diethyl ether:n-pentane (2:1, v/v) mixture. The solvent extraction technique was simpler and faster than the purge and trap method, taking 5 seconds rather than 1 hour; it was also more efficient, resulting in 1.7 fold more total volatiles with better reproducibility. Application of hypoxic gas atmosphere to apples (100% CO2, 100% N2 or < 2.5% O2) demonstrated consistently enhanced headspace acetaldehyde, ethanol and ethyl acetate in 'Granny Smith', 'Braeburn' and 'Red Delicious' cultivars. A marked increased production of ethanol in response to hypoxic treatments was always followed by a several fold enhancement in both number and concentration of ethyl esters, including the aroma-impact volatiles ethyl butanoate, ethyl 2-methyl butanoate and ethyl hexanoate in juice from all cultivars. The increased concentration of these compounds was accompanied by decreased production of other esters requiring the same acyl group for their synthesis, such as propyl butanoate, butyl acetate and hexyl acetate, and some alcohols and aldehydes, including hexan-1-ol, 2/3-methyl butan-1-ol and trans-2-hexenal. These results confirmed the hypothesis of the competitive nature of the acyl esterifying system in apples. Exposing apples to 100% CO2 for 18 - 24 hours at 20°C achieved optimum enhancement; a longer time (48 hours) did not further increase important aroma-impact ethyl esters but caused a marked reduction in non-ethyl esters, while a shorter period of exposure (6 - 12 hours) had minimal effect. Apples previously stored (0°C) for 6 months or longer before exposure to hypoxic treatments did not have important volatile ethyl esters enhanced. Application of 1000 ppm ethylene for 24 hours did not increase volatile production in apples compared with non-treated fruit. Poststorage production of most aroma volatile compounds from 'Granny Smith' and 'Fuji' apples stored in a controlled-atmosphere (CA) of 2% CO2 + 2% O2 at 0.5°C was depressed after 10 - 14 weeks storage, although 2-methyl butan-1-ol was enhanced and there was no effect on trans-2-hexenal. Poststorage treatment with 100% CO2 (24 hours at 20°C) consistently and markedly enhanced headspace acetaldehyde, headspace ethanol, headspace ethyl acetate and aroma impact compounds, ethyl butanoate, ethyl 2-methyl butanoate and ethyl hexanoate in fruit from both refrigerated air (RA) and CA storage regimes. The hypoxic treatment had no effect on production of butan-1-ol and hexan-1-ol in CA, or hexanal in RA 'Granny Smith', propan-1-ol and butan-1-ol in either RA or CA, or hexanal and trans-2-hexenal in RA 'Fuji' apples. Hypoxic treatments reduced production of butyl and hexyl acetate in 'Fuji' apples, and 2-methyl butan-1-ol in both cultivars. The ability to sustain enhanced production of ethyl esters in CO2 treated RA or CA 'Granny Smith' or CA 'Fuji' apples decreased as time of storage progressed, probably due to shortage of acyl CoA substrates for volatile synthesis. CA retarded flesh softening and acid loss in both cultivars. Examination of volatile production from 6 commercial apple cultivars established that esters, alcohols and hydrocarbons accounted for 70% - 88% of the total number of volatiles found and compounds with straight chain and even numbered carbons predominated in the composition of esters and alcohols. Differences among apple cultivars were associated with number and concentration of volatile compounds produced. Treatment with 100% CO2 (24 hours at 20°C) consistently enhanced production of headspace volatiles in all cultivars. Production of aroma impact ethyl esters following hypoxic treatments consistently occurred with 'Red Delicious', 'Braeburn', 'Granny Smith' and 'Pacific Rose', with less of a response in 'Cox's Orange Pippin' and none in 'Royal Gala' apples. Non ethyl esters and alcohols, other than ethanol and propan-1-ol, were reduced after CO2 treatment in all cultivars, except for butan-1-ol in 'Cox's Orange Pippin' apples. Hexanal and trans-2-hexenal were either reduced or not affected following CO2 treatment, depending on cultivar. The magnitude of enhancement and the degree of reduction in production of aroma volatile compounds following hypoxic treatment varied among cultivars; the higher the magnitude of enhancement of ethyl acetate, the greater the degree of reduction in other acetate esters, supporting the concept of a competitive interaction in the acyl esterification in apples. Hypoxic treatments consistently caused profound increases in aroma volatiles in most apples cultivars studied. Such a treatment has potential to increase the strength and value of commercially important flavour fractions in apple juice and aqueous essence and enhance aroma in fresh apples.Item Factors influencing the susceptibility of apples to bruising : this thesis is presented in partial fulfilment of the requirements of the degree of Doctor of Philosophy in Horticultural Science at Massey University, Palmerston North, New Zealand(Massey University, 1997) Mowatt, Craig Meffan; Mowatt, Craig MeffanFinancial returns to New Zealand orchardists could be increased if bruise damage to apples and its visual consequences were reduced. Comprehension of the variability of susceptibility to the bruising of apples associated with either preharvest, harvest or postharvest influences is fundamental to reducing bruise damage. Standard impacts to apples have been generated in many ways and bruise severity has generally been represented as bruise volume per unit energy. In this study bruise severity was represented by a) the diameter of a bruise generated by a sphere of mass and radius of curvature similar to that of apples and whose impact energy (0.32 J) was similar to apple-apple collisions that occurred during grading or b) the damage that apples incurred by grading in a standard manner. Bruise colour was also measured and visual differences between dark and light brown 'Granny Smith' bruised tissue were associated with a 5° difference in hue angle, as measured by a Minolta chromameter. In 1990 from a survey of 'Granny Smith' orchards it was determined that the range in bruise diameter of individual fruit was 17% (fruit mass range; 0.157-0.207 kg) and in 1991 was 63% (fruit mass range; 0.098-0.278 kg). The between-season difference in mean bruise diameter was 2.8%. Over the two years it was found that bruise diameter of fruit from orchards producing either the most or least bruise susceptible fruit differed by an average of 6.5%. In 1991 bruise diameter generated from a standard impact was related to grader damage (R2 = 0.49) and the slope of this relationship indicated that small increases in bruise diameter equated to large increases in grader damage. In both years the most bruise susceptible fruit had higher levels of tissue phosphorus, calcium and nitrogen than least susceptible fruit. In one year of the survey bruise diameter was positively related to apple calcium content and apple mass with grader damage positively related to phosphorus content. In a within-orchard study between-tree variation in bruise diameter of 'Royal Gala' (11%) exceeded that of 'Granny Smith' (4%). Bruise diameter of least bruise susceptible fruit was more consistently related to starch index, soluble solids, fruit mass and firmness than bruise diameter of the most susceptible fruit. Harvesting 'Granny Smith' and 'Royal Gala' early rather than later in the season resulted in bruise diameter reductions of 5% and 21% respectively. Within-tree position of apples did not consistently influence susceptibility to bruising in either variety. Foliar sprays of calcium (CaCl2) and phosphorus (H3PO4) did not influence fruit mineral contents or susceptibility to bruising. Apples from non-irrigated "Braeburn" trees had smaller bruise diameters (6%), less calcium and tended to have more dry matter than apples from normally irrigated trees. 'Golden Delicious' apples harvested later in the day were less susceptible to bruise damage (7.3%) than those harvested early in the morning; elevated temperatures and reduced water status were identified as causative factors. As temperature increased from 0 to 20°C susceptibility to bruising showed a non-linear reduction. Bruise diameter and grader damage reduced 5% and 24% respectively when 'Granny Smith' apples were bruised at 20°C rather than when bruised at 0°C. If 'Royal Gala' were cooled to 2°C and then rewarmed to 20°C they sustained 36% less grader damage than if graded immediately after harvest. Useful reductions in grader damage (25%) were achieved by holding freshly harvested 'Royal Gala' at ambient temperatures for one day before grading. Storing the bruise susceptible cultivar 'Splendour' apples for 54 h at 20°C before bruising resulted in a 9% reduction in bruise diameter. A 24 h delay in pre-cooling of 'Royal Gala' was associated with a 0.5% weight loss and a 3% reduction in bruise diameter; delays of more than 24 h before pre-cooling were associated with enhanced ripening and greater weight loss but no measurable change in susceptibility to bruising. In the 1991 survey, there were large between-orchard differences in hue angle of bruised 'Granny Smith' apple tissue (16°) and light brown bruise tissue was associated with higher fruit nitrogen content (R2 = 0.55). Between-tree differences in hue angle of bruised tissue from 'Royal Gala' apples were large (15°) but with 'Granny Smith' were insignificant. Differences in bruised tissue colour due to enhanced maturity or within-tree position in both cultivars were not consistent. Cool storing 'Splendour' for 414 h before bruising appeared to increase bruise lightness.