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Item The oxidation of [alpha]-farnesene : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Chemistry at Massey University(Massey University, 1994) Spicer, Julie AnnAutoxidation products of the sesquiterpene α-farnesene 1 increase rapidly in apples during cold storage and are believed to play an important role in the production of the cold storage disorder, superficial scald. The site selectivity of the oxidation of α-farnesene was investigated with a variety of useful reagents for photochemical allylic oxidation, hydroxylation and epoxidation. Oxidation products 33-47 were isolated and characterised. The synthesis of conjugated trienes and related oxidation products of α-farnesene 1, principally from the epoxides of α-farnesene, is described. Base-promoted ring opening of 6,7-epoxide 44 by the mixed base potassium tert-butoxide / lithium disopropylamide afforded the conjugated triene 3 whilst the 3,4-epoxide 45 afforded triene 50. In contrast, 10,11-epoxide 43 failed to undergo epoxide ring opening; rearranging instead to the conjugated triene epoxide 51. Base-promoted ring opening of bis-epoxide 46 afforded trienol epoxide 56 at -30°C, whilst cyclisation to tetrahydrofurans 55a and 55b occurred at room temperature. Photosensitised oxidation of 10,11-epoxide 43 followed by in situ treatment with acid gave the cyclic peroxide 4 and upon reduction, tetrahydrofurans 55a and 55b. Bisallylic alcohol 61 was prepared by alkylation of 3-methylsulpholene 29 with geranial 59 followed by thermolysis. Trienes 3 and 4 have been isolated previously as autoxidation products of α-farnesene 1 and are implicated as the causal agents of the superficial scald of stored apples. The asymmetric dihydroxylation of α-farnesene 1 using the Sharpless ligands (DHQ)2- PHAL and (DHQD)2-PHAL was investigated. The isolation and characterisation of the 3,4-, 6,7- and 10,11-diols 41,42 and 114 as well as the tetraol 115 is described. High enantioselectivity and preferential addition to the 6,7-olefin was observed. The isomeric β-farnesene 2 showed a preference for reaction at the 10,11-position. The enantioselective synthesis of an apple aroma constituent, bicyclicacetal 17, is described. Asymmetric dihydroxylation of 6-methylhept-5-en-2-one 15 was carried out using the ligands (DHQ)2-PHAL and (DHQD)2-PHAL according to the method of Sharpless. Acid-catalysed cyclisation then afforded the required acetal 17 in high enantiomeric excess. Enantiomeric excesses were measured using chiral solvating agent 113 and/or synthesis of the corresponding Mosher ester derivatives, followed by 1H or 19F nmr.Item Mathematical modelling of heat transfer and water vapour transport in apple coolstores : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Biotechnology and Bioprocess Engineering at Massey University(Massey University, 1995) Amos, Nevin David; Amos, Nevin DavidA study of heat transfer and water vapour transport in a large industrial apple coolstore was undertaken. A set of measurements was made including product cooling rates in both pre-cooling units and the bulk-storage area, evaporator and fan performance, floor and building shell temperatures, door opening frequency and air temperature, relative humidity (RH) and velocity variation with both position and time. Measurements within pallet pre-coolers showed large variations in product cooling rate, between apple cartons but this could not be attributed to any positional factor studied. The spread of data was probably due to widely differing airflows through and around each apple carton. A staggered pallet pre-cooler configuration had a 30% faster cooling rate on average than an in-line pallet arrangement. Measurements of cooling rates within single cartons showed large variation of cooling rate with position within a carton, probably resulting from non-uniform airflow within the carton. Existing heat conduction-based models were unable to predict the level of variability of cooling rate within cartons. A multi-zoned conduction and convection model was developed which predicts apple temperature and weight loss, air temperature, enthalpy and humidity, and packaging temperature with position within the carton. Testing of the model against measured data showed good fit for air and apple temperatures, but insufficient data were available for comprehensive testing of the humidity and weight loss sub-models. Difficulties in developing methodology to accurately define the patterns of airflow within cartons were not adequately overcome, so measurements to determine airflow patterns would be required before predictions could be made for alternative packaging systems. Within the coolstore measured there was significant positional variation in air temperature and humidity associated with local heat sources (such as pre-coolers, doors, uninsulated floor, and warm fruit batches), and the degree of air circulation as quantified by local air velocities. In addition, temperature and humidity showed a diurnal fluctuation associated with the operation of the coolstore. These results suggested the need for a multi-zone dynamic model to enable predictions of both the time and the positional variation to be made. Such a model was developed which included component models for zone air, external surfaces, floors, heat generators, inert materials such as internal structural components, evaporators, fans, doors and product. Novel features of the model compared to existing models are that it estimates airflow between zones using fixed user defined pathways, rather than complex hydrodynamic models; it considers water vapour transport in detail as well as heat transfer; condensation on surfaces and water absorption by packaging are modelled; and the product sub-model both allows movement of product batches during the simulation and accounts for differences in cooling rate within a batch. Single-zone, 5-zone, 8-zone and 34-zone versions of the model were tested. The 1-zone model predicted mean thermal conditions for the coolstore adequately. The 5-zone model which differentiated the pre-coolers and the bulk-storage area predicted measured data well for the pre-coolers, but more time-variability was predicted for the bulk-storage area than occurred in the measured data. Separate door zones and vertical subdivision of the bulk-storage area were allowed in the 8-zone model. The pre-cooler prediction was largely unchanged and predicted vertical temperature differences were consistent with measured data, but the predicted mean temperature in the bulk-storage area was offset from the measurements. Little accuracy improvement was achieved by further subdivision (up to 34 zones), probably because of imprecision in defining and predicting interzone airflow rates. Irrespective of the number of zones, adequate air humidity predictions could only be achieved when water absorption by packaging was modelled as well as product weight loss, door infiltration and deposition of moisture on evaporators. For the industrial coolstore studied use of 5 or 8 air zones appeared to be the best trade off between accuracy and complexity. The model allows study of the effect of design and operational features on coolstore air temperature, humidity, product temperature and weight loss with better accuracy than previous models.Item 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 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 characteristics and quality 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, 1992) Dadzie, Benjamin Kwesi; Dadzie, Benjamin KwesiAtmospheric modification can extend the storage life of harvested fruits and vegetables beyond that which can be achieved with refrigerated air storage alone. Apples are particularly well suited to modified atmosphere (MA) storage and yet the recommended atmospheres for different cultivars of apples vary widely and responses of individual populations of apples to a given treatment can be variable. Part of this variation may be related to the variability in the internal atmosphere composition of individual fruit. This thesis explores the relationships between internal atmosphere composition of apples and factors such as skin resistance to gas diffusion (R), respiration, external oxygen concentration ([O2]ext), temperature and artificial barriers, all of which can influence the outcome of a given MA treatment. Skin resistance to gas diffusion (R) values of freshly harvested apples of eight cultivars grown in New Zealand, were obtained using non-steady state and steady state methods at 20±1°C. R was cultivar dependent, with freshly harvested Braeburn apples having the highest mean R and Royal Gala the lowest. Skin resistance to ethane diffusion (RC2H6) was linearly related to skin resistance to ethylene diffusion (RC2H4) for individual apples within cultivars. Although there was a large degree of variation in between pairs of R values obtained on different apples within each cultivar, individual R values within these pairs were very similar to each other. The close relationship between the two independent estimates of R confirmed that this was real fruit to fruit variation rather than measurement error. In contrast, estimates of skin resistance to carbon dioxide diffusion (RCO2) were consistently higher than values for RC2H4. There was a curvilinear relationship between RCO2 and RC2H6 in a combined data set for all cultivars, indicating that CO2 may diffuse through additional routes to those available for O2, C2H4 and ethane (C2H6). Freshly harvested Cox's Orange Pippin apples were respiring nearly twice as fast as Splendour, Granny Smith or Braeburn apples and a third higher than Gala, Royal Gala and Golden Delicious apples. Respiration rate appeared to be independent of RC2H6 both within individual cultivars and in a combined data set for all cultivars. On the other hand, there was a declining exponential relationship between [O2]i and RC2H6 for individual apples and an increasing relationship between [CO2]i and RC2H6. Thus, the magnitude of R affects internal atmosphere composition for a given external atmosphere. The respiratory and C2H4 production responses of Cox's Orange Pippin and Granny Smith apples to reduced O2 concentrations were characterised by studying the variation in the magnitude of O2, CO2 and C2H4 concentration differences between the internal and external atmospheres (Δ[O2], Δ[CO2] and Δ[C2H4]) of individual apples maintained in different O2 atmospheres at 20±1°C. Δ[O2] decreased at low O2 levels, reflecting the decreased rate of O2 uptake in low O2 concentrations. Oxygen uptake relative to that in air (RelO2) approximately followed Michaelis-Menten kinetics, with a half-maximal rate of 2.5% O2 for [O2]i and 7.5% for [O2]ext. A mathematical equation was developed to describe the two physiological processes (ie. anaerobic and aerobic respiration) involved in the relationship between relative rate of CO2 production (RelCO2) or internal CO2 concentration ([CO2]i) and [O2]ext or [O2]i. The equation had two components, each describing one of the two physiological processes. The relationship between relative rate of C2H4 production (RelC2H4) or internal C2H4 concentration ([C2H4]i) and [O2]i was more closely described by an exponential rather than a Michaelis-Menten type hyperbolic curve. Nevertheless, the overall shape of the relationship conformed to the expectation that small changes in O2 concentration would have much greater effect at low [O2]i than they do at high [O2]i. In contrast, the presence of the skin as a diffusion barrier (R) resulted in development of an apparent 'lag phase' in the relationship between RelC2H4 or [C2H4]i and [O2]ext such that it was no longer described by an exponential type curve and became essentially sigmoidal. These differences are attributable to gradients in gas composition between internal and external atmospheres. Washing of Granny Smith apples in Tween 20 solutions inhibited development of greasiness. This effect was associated with increased R, depressed [O2]i, lower respiration and increased [CO2]i and [C2H4]i in the washed fruit compared to controls. The depression of [O2]i in Tween 20 treated fruit was greater than the elevation of CO2, suggesting that the Tween 20 treatment may have affected CO2 production and O2 uptake to different extents or alternatively the Tween 20 deposit on the fruit surface was differentially permeable to these two gases. Washed fruit also remained greener and firmer than controls. Pre-treatment by wiping without using Tween 20 solution had none of these effects but did stimulate weight loss. None of the treatments induced internal browning which is often associated with the development of greasiness in Granny Smith apples. The relationship between temperature and R, internal atmosphere compostion, respiration and rate of C2H4 production of eight cultivars of apples was ascertained after equilibrating fruit at temperatures ranging from 0 – 30°C for 72h. R appeared to be independent of temperature. [O2]i decreased, while [CO2]i increased, in response to increasing temperatures and varied with cultivar. Braeburn apples consistently had lower [O2]i and higher [CO2]i than the other cultivars while the converse applied for Splendour apples. Internal C2H4 concentrations ([C2H4]i) and rate of C2H4 production increased with increasing temperatures to a maximum at 25°C, above which internal concentrations and rates of production declined. The magnitude of decline was cultivar dependent. Compared to the other cultivars, Splendour apples had the least capacity to accumulate and produce C2H4. There was a progressive increase in fruit respiration rate with increasing temperatures, which varied with cultivar. Over all the temperature regimes, Splendour had the lowest average respiration rate while Cox's Orange Pippin apples had the highest. The potential for variability in these gas exchange variables being associated with overall storage life and response to MAs is discussed. Small gas concentration differences were measured between the equator and calyx end, and between the equator and calyx end shoulder within individual fruit in Golden Delicious, Red Delicious, Granny Smith and Splendour apples at 20±1°C. In contrast, large O2 and CO2 concentration differences between the same positions were found in Gala, Royal Gala, Braeburn and Cox's Orange Pippin apples. The differences were much greater than those measured between the core cavity and the fruit surface. Similarly, tissues in the calyx region of Braeburn and Granny Smith apples consistently had lower O2 but higher CO2 and C2H4 concentrations than any other position on the fruit surface, whilst tissues at the equator had higher O2 and lower CO2 and C2H4 concentrations than other parts of the fruit. These data falsify the notion that the internal atmosphere of individual apples can be regarded as being homogeneous. The heterogeneous distribution of gases within individual fruit would presumably affect the tendency of individual tissues to develop low-O2 or high CO2 disorders, particularly for fruit stored in MAs at elevated temperatures. A conceptual model is presented which summaries the relationships between fruit [O2]i and [O2]ext, R, respiration, temperature and artificial barriers. The [O2]i of apples are always lower than the [O2]ext used during MA storage, to an extent which is determined by the respiratory O2 uptake by the tissues coupled with R. With everything else being maintained equal, increased R or increased respiration rate therefore depresses [O2]i which in turn modifies the extent of response of the crop to a given MA treatment. These variables are therefore all important in determining the fruit's response to atmospheric modification.