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    An examination of postharvest techniques to enable seafreight export of feijoa (Acca sellowiana [O.Berg.] Burret) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Manawatu Campus, Palmerston North, New Zealand
    (Massey University, 2020) Oseko, Jacqueline Kwamboka
    Export of feijoa (Acca sellowiana [O.Berg.] Burret) to the main markets in Europe, Asia and North America is currently by airfreight that is not only expensive but rather unsustainable as the industry expands. With the ongoing breeding works and expansions of plantings, growers will eventually have to seek for an economic mode of transport. As is the case with kiwifruit, apples, avocadoes, and squash, seafreight will provide an alternative option that is both cheaper and accommodates large fruit volumes. The short storage life of feijoa, however, is likely to pose a challenge to seafreight (that requires at least 6 weeks of storage) if appropriate postharvest techniques are not identified to extend storage life. Feijoa stores for about 4 weeks at 4 °C after which it becomes overripe, loses flavour, and develops chilling injury and internal browning. This study was undertaken to examine potential postharvest techniques that could extend storage life and maintain quality of feijoa. The postharvest techniques investigated were temperature and relative humidity management, harvest timing, step down conditioning, intermittent warming, chlorophyll fluorescence and development of non-destructive grading tools. The varieties used in this study were ‘Kakariki’, ‘Wiki Tu’ and ‘Triumph’ that were stored for 8 weeks under various conditions. To assess the effects of temperature and relative humidity in storage, ‘Kakariki’, ‘Wiki Tu’ and ‘Triumph’ were stored at 1 °C (85% RH) and 4 °C (88% RH). These conditions were set to result in equal water vapour pressure deficits at both temperatures. The effects of RH on feijoa quality during 8 weeks storage were tested by using a polyethylene liner (polyliner) to cover the fruit in each tray, for half of the treatments. Despite good retention of some attributes indicating quality (firmness and skin colour) for up to 8 weeks at 1 °C, many fruit developed chilling injury making it unsaleable and therefore causing huge losses. At both 4 °C and 1 °C the use of a polyliner resulted in reduced water loss, suggesting polyliners may be beneficial for feijoa storage. Given the chilling injury results, it is imperative to consider treatments that may reduce chilling injury and yet maintain fruit quality. To alleviate chilling injury and extend storage life of ‘Kakariki’, 2 harvesting times (early (H1) and commercial (H2)), 2 storage temperatures (2 °C and 4 °C) and three conditioning treatments (single step down, [6 d at 9 °C then moved to 2 °C or 4 °C ], double step down [3 d at 9 °C , 3 d at 6 °C then moved to 2 °C or 4 °C] and ‘no conditioning’ control [stored direct to 2 °C or 4 °C]) were established. Results showed that early harvested fruit had lower chilling injury incidence and retained more quality attributes thereby providing a possibility of extending Kakariki’ feijoa storage life. There was no evidence for a difference in quality arising from storage at 2 °C or 4 °C but it was evident that single or double step down conditioning simply allowed an extended period of postharvest ripening because of the 6 d delay in reaching the more appropriate storage temperature of 2 °C or 4 °C. This led to faster deterioration of fruit. Therefore, it is advisable to rapidly cool feijoa soon after harvest to reduce metabolism and ripening; but then sell the fruit before they develop CI. To assess the effects of intermittent warming (IW) on improving quality of ‘Triumph’ fruit. Three (3) intermittent warming conditions were tested (IW from 4 °C to 20 °C for 1 d after every 6 d storage, IW from 4 °C to 20 °C for 1 d after every 10 d storage and control) and stored at 4 °C for 6 weeks. Chlorophyll fluorescence was used as a non-destructive tool to assess quality. The results showed that intermittent warming just like conditioning treatments, accelerated ripening leading to faster deterioration. A decline in quantum yield (Fv/Fm) was observed during storage in the absence of CI. This suggests that it is linked to loss of chlorophyll content and chloroplast membrane injury associated with photosystem II (PSII) as feijoa ripened. The continuous decline in quantum yield (Fv/Fm) offers potential for a non-destructive technique to assess feijoa ripeness and could therefore be used in a cool store to detect batches of fruit that are ripening more quickly for immediate sales or those ripening slowly that may be more suited to export or long storage. To re-evaluate the internal maturity/ripeness scale developed by scanned images of ‘Kakariki’, ‘Wiki Tu’ and ‘Triumph’ varieties from at harvest through storage were assessed against the PFR scale. The results showed that the PFR scale worked well for maturity assessment of ‘Kakariki’, ‘Wiki Tu’ and ‘Triumph’ varieties at harvest, despite their quite different internal anatomy. The same scale was also appropriate for each variety as a post-storage ripeness indicator. Evidence also suggested that one new step was required an internal maturity rating of 1.5. The problem was that fruit at stage 1 could be immature (and not ripen during storage) or mature. This new stage was used to describe fruit showing the first signs of locular gel clearing, suggesting that ripening was definitely underway. Firmness (non-destructively assessed) at harvest was correlated with quality after storage and therefore showed potential to predict fruit ripening behaviour in storage. This implies, that firmness could be used non-destructively in sorting lines to select firm fruit for long storage or soft fruit for immediate consumption. Based on these findings’, storage life of ‘Kakariki’, ‘Wiki Tu’ and ‘Triumph’ feijoa could not be reliably extended beyond 4 to 6 weeks and therefore seafreight export is still risky. The wide range of maturity variation within any batch of harvested feijoas accounts for much of this risk. Future research should focus on finding a rapid, non-destructive technique that can detect the new internal maturity/ripeness rating 1.5. This would assist growers to grade early harvested fruit and select mature but longer-storing fruit for export.
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    Non-destructive measurements of internal maturity of Feijoa (Acca sellowiana) : a 90 credits thesis presented in partial fulfilment of the requirements for the Master degree of AgriScience in Horticulture at Massey University, Palmerston North, New Zealand
    (Massey University, 2015) Duan, Yuwei
    Feijoa (Acca sellowiana) is a delicious fruit with a narrow window for harvest and a limited postharvest life. In New Zealand, feijoa fruit is required to have at least 6 weeks postharvest life in cool storage plus 6 days shelf life under room temperature in order to be exported to global markets. Slightly immature feijoa fruit (maturity stage 2) can be stored for more than 6 weeks plus few days’ shelf life. However, the variation of maturity is large even among individual fruits harvested from the same tree at the same time, and currently, there is no way to segregate fruit non-destructively based on the internal maturity of feijoa at harvest time. The problem with current industry segregation practice is that the external features of feijoa, such as shape, size, and weight cannot segregate fruit with different maturity. It is inevitably that some more mature fruit will rot quickly and affect overall batch quality during storage. It is vital to have a non-destructive assessment of fruit internal maturity at harvest time. Then fruit with different maturity can be divided into different batches with more mature fruit put on sale on local market and less mature fruit put into storage. As a result, the fruit loss rate and overall fruit quality can be improved. Therefore, in this study, efforts were made to explore a non-destructive method to estimate the internal maturity of feijoa fruit and correlate that maturity with performance during storage. The non-destructive measurements in this experiment included fruit weight, compression firmness, and skin colour. Four feijoa varieties: ‘Kakariki’, ‘Barton’, ‘Anatoki’, and ‘Wiki-Tu’ were selected for this experiment. For each variety, 945 fruit samples were harvested at approximately one week before becoming fully mature (standard commercial harvesting) and sent to the lab in Massey. All the fruit were divided into three groups based on their skin colour (from darkest green to lightest green). 45 fruit (three replicated batches of 15) from each colour group were measured immediately for weight, firmness, maturity, skin colour, Brix, and titratable acidity (TA). Then all the other fruit samples from the same colour group were randomly divided into three groups that were kept in cool storage for 4 weeks, 6 weeks and 8 weeks respectively. Once cool storage was completed, those samples were taken out and firmness and skin colour were measured (non-destructive measurements). Then all the samples were retained at 20°C. Half of these fruits were assessed for quality attributes 3 days later, and the other half were measured 6 days after cool storage. All fruit were cut open for final visual assessment of maturity according to the maturity index developed by Plant & Food Research Institute. The data of internal maturity and initial fruit quality (weight, firmness, and skin colour) for each fruit was used to draw scatterplots in order to find out the correlation between estimated maturity at harvest, final fruit internal maturity and fruit quality after storage. The correlation (R2) between internal maturity and compression firmness found on ‘Kakariki’ was 0.6 to 0.5. The correlation for ‘Barton’ and ‘Wiki-Tu’ was weaker than that of ‘Kakariki’ (R2 from 0.6 to 0.2). The correlation between firmness and internal maturity for samples of ‘Anatoki’ were weak. The simulated segregation based on firmness for ‘Kakariki’ and ‘Barton’ indicated that the firmness segregation at harvest time could be very useful on eliminating potentially bad fruit during cool storage. A non-destructive method for ‘Kakariki’ and ‘Barton’ fruit based on initial firmness is therefore now available that would allow successful segregation of fruit with potential for long term storage. However, this segregation would not work well on ‘Anatoki’. No significant correlation was found between skin colour, fruit weight and the internal maturity of feijoa fruit either at harvest time or after storage. There was a very large variation in fruit quality at harvest time and during the storage periods. Samples of ‘Wiki-Tu’ indicated that this variety could have the best storage performance among the 4 varieties testes. ‘Anatoki’ may also have a reasonable storage potential with less flavour. The feijoa fruit may not be stored well when covered with polyethylene film, as it may harm the storability of the fruit. Too immature fruit should not be harvested as well, as it would never be able to ripen properly during the postharvest period.
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    Concentration of feijoa and boysenberry fruit aroma condensates using pervaporation : a thesis presented in partial fulfillment of the requirements for the degree of Master of Food Technology at Massey University
    (Massey University, 2000) Yang, Meifang
    This present work aimed to investigate pervaporation for aroma recovery and concentration from fruit aroma condensate collected during evaporation of fruit juices. A 5% ethanol solution, feijoa and boysenberry aroma condensates were concentrated in a pervaporation apparatus fitted with polydimethyl siloxane (PDMS: GFT1060, GFT1070) and poly-ether-block-amide (PEBA, GKSS) membranes, under the following operating conditions: feed temperature of 30°C, feed flow rate of 8.3 x 10 or 1.4 x 10 , and permeate pressures of 100 Pa or 1000 Pa. Feijoa and boysenberry aroma condensates were also concentrated by vacuum distillation. Aroma compounds and their concentrations in the feed, retentate and permeate were identified and determined by gas chromatography (GC) and a mass spectrometer coupled to a GC. The three membranes investigated for pervaporation gave different total fluxes, partial fluxes, mass transfer coefficients, enrichment factors and aroma compositions for feijoa and boysenberry condensate. PEBA membranes proved to have best performance for concentration of feijoa and boysenberry aroma due to high enrichment factors and mass transfer coefficients for the important aroma compounds of both feijoa and boysenberry. Increasing the feed flow rate from 1.1 x 10 to 1.4 x 10 did not affect the total flux, but increased significantly the partial fluxes and enrichment factors of preferentially permeating compounds such as methyl benzoate, ethyl benzoate and linalool. Decreasing permeate pressure significantly increased the total flux, the partial fluxes and enrichment factors for higher boiling aliphatic alcohols. The mass transfer resistances of methyl benzoate, ethyl benzoate and linalool was dominated by the boundary layer effects. The mass transfer resistances of high boiling aliphatic alcohols, hexanol, Z-3-hexenol and E-2-hexenol were strongly influenced by permeate pressure. Compared with vacuum distillation, pervaporation showed better performance for producing concentrated feijoa and boysenberry aromas which were highly enriched in the important flavour compounds for each fruit.
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    Manipulating harvest maturity and ethylene to extend storage life of feijoa : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand
    (Massey University, 2015) Rupavatharam, Srikanth
    In New Zealand feijoa (Acca sellowiana) are harvested by touch-picking and can be stored at 4 °C and 90% RH for up to 4 weeks with a subsequent shelf life of 5-7 d at 20 °C. Extending the storage potential of feijoa can enable export to new marketplaces through sea freight. The objective of this work was to extend the storage life of feijoa. Harvest maturity, variability within batch and ethylene all have the potential to influence postharvest storage performance. Harvesting feijoa earlier not only makes touch-picking irrelevant but will necessitate changes to the present grading standards of feijoa. Harvesting feijoa 2 weeks prior to touch-picked maturity consistently enabled storage life extension for up to 6 weeks at 4 °C with a subsequent shelf life of 5 d at 20 °C. However, these fruit were low in SSC with high TA suggesting that their taste profiles may be altered and hence a consumer taste acceptance investigation is recommended. There is also a need to identify a ripening index for feijoa while redefining grading criteria suitable for both local and export markets. This work demonstrates that feijoa having higher °hue (> 122) at the time of harvest possessed longer storage potential than those with lower °hue (< 122) that are ready-to-eat. Blocking ethylene responses of touch-picked or early harvested feijoa by postharvest 1-methylcyclopropene treatment had minimal effect on physiology (ethylene production and respiration rates) or quality after storage. Feijoa were also insensitive to exogenous ethylene application while CA technology stimulated surface injury. However preharvest Aminoethoxyvinyl glycine (AVG) application reduced fruit drop and delayed maturity (retaining firmness) of feijoa at the time of commercial harvest. AVG suppressed ethylene production during storage without altering quality attributes (firmness, SSC, TA or flesh colour). A conceptual model was developed to summarise feijoa responses to ethylene manipulations. Postharvest ripening in feijoa appears to be substantially ethylene-independent. Storage life of feijoa was extended by harvesting fruit earlier than current touch-picking maturity. Segregating feijoa by skin colour change would allow sea freight of less mature fruit. However, taste acceptance of these fruit and commercial trials of preharvest AVG are required before practical recommendations can be made to the industry.
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    Postharvest treatments to extend the storage life of feijoa (Acca sellowiana) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand
    (Massey University, 2010) Al-Harthy, Abdul-Aziz Salim
    Feijoas (Acca sellowiana) have a short harvest season and a limited postharvest life. In feijoa, usually there is a large variation between individual fruit in terms of size, colour, chemical composition and physiological stage. This variation could be attributed to the time of fruit set which is relatively long, which leads to great variation in fruit maturity. In order for the New Zealand feijoa industry to export to distant markets a postharvest life of at least 6 weeks is required. Determining the maturity index of a crop is vital especially for trade regulations and marketing strategy. Feijoa do not change colour significantly during ripening, so the only unequivocal way of assessing fruit maturity is to cut the fruit open. An internal maturity rating scale has been developed by Plant and Food Research primarily based on locular development. The use of ‘touch picking’ depending on fruit retention force is considered the most practical and reliable method for the time being for determining minimum harvest maturity of feijoa. The aims of this work were to investigate options for a non-destructive method in determining maturity index of feijoa fruit compared to the internal maturity rating scale; extending storage life of feijoa fruit by cool storage and controlled atmosphere conditions to allow long distance sea freight to increase export opportunities; and to develop an understanding of feijoa ripening physiology in relation to ethylene and propylene treatments. In this study, differences between the commercial pack houses in identifying the optimum fruit maturity of feijoa at harvest were large. Compression firmness was more reliable than acoustic firmness in determining maturity stages of different feijoa cultivars, but acoustic firmness was quite reliable for some cultivars. The Sinclair unit device was not suitable for measuring maturity index of feijoa fruit tested. Spin-spin relaxation time (T2) and half height peak (ΔH2) determined by NMR showed promise for identifying fruit maturity. In general, these non-destructive techniques used in this experiment showed some promise but further work is required to understand why the differences between cultivars and regions happen. Chemical changes such as total soluble solids, dry matter and titratable acidity were found unhelpful in determining maturity stages of feijoa fruits. There was no significant reduction in TSS or dry matter with maturity, but there was a clear reduction in titratable acidity. Even with this clear trend with titratable acidity, it is not helpful as it is still a destructive measurement, nevertheless the internal chemical changes may be able to be estimated with a non-destructive technique such as Near Infrared Spectroscopy (NIRS). A combination of non-destructive methods such as firmness with NIR may be better than depending on a single index in identifying fruit maturity. In addition, the data clearly demonstrated that fruit at any particular internal maturity rating were clearly shown to have a wide range of firmness values, total soluble solids (TSS), titratable acidity (TA), skin colour, and aroma. This makes it likely that this maturity as measured by locular development is a poor descriptor for overall process of fruit ripening in feijoa. As feijoa fruit mature, aroma volatile concentrations increase. The three characteristic compounds (ethyl butyrate, ethyl benzoate and methyl benzoate) of feijoa aroma were found more consistently in headspace analysis than solvent extracted flesh. Controlled atmosphere (CA) storage was found to suppress volatile production. Aroma could be used as a fruit quality measure. The e-nose has been shown to be sensitive to volatiles in other fruit, so it might have potential for measuring the changes in maturity of feijoa fruit. This technique is practical, non-destructive and cost effective. This technique should be tried in the future with feijoa cultivars. To extend the postharvest life of feijoa fruit, cool storage in unlined trays at 4°C was tested. During cool storage, weight loss increased to about 6% after six weeks at 4°C and additional 5% during 7 days of storage at ambient temperature (20°C). Firmness (acoustic and compression) and other aspects of fruit quality decreased with time. Rate of ripening as measured by the change of internal maturity rating at 20°C increased with time. No significant changes were found in terms of total soluble solids during subsequent shelf life at 20°C for the entire period of storage. ‘Unique’, an early cultivar, generally had a shorter storage life than ‘Opal Star’. The effects of five controlled atmospheres were also studied. Fruit were stored in a matrix of two levels of oxygen (2% and 5%) and two levels of carbon dioxide (0% and 3%), or air control, at 4°C for 10 weeks. Fruit were transferred to ambient temperature (20°C) after storage for 4, 6, 8 and 10 weeks for shelf life assessment for 7 days. For the entire period of storage, fruit weight loss was approximately 1.5-2% of the initial weight. The firmness of the fruit stored under CA conditions decreased regardless of atmospheric conditions. In ‘Opal Star’, fruit underwent a significant colour change from dark to light green after the 10 weeks of storage. However, for ‘Unique’ there was no significant change in colour observed in the period tested. In both cultivars, there was a slight decrease in TSS over time. ‘Opal Star’ showed a good storage life with better fruit acceptability as compared to ‘Unique’. In both cultivars, all the treatments caused some signs of injury after week 6. Generally, CA conditions were effective in reducing weight loss and external injury, and maintaining fruit firmness compared with air. ‘Opal Star’ had a good storage life with over 60% of fruit rated acceptable after 73 days of storage in CA treatments without CO2. Hence ‘Opal Star’ may be suitable for export by sea. The effect of three concentrations of ethylene (10, 100 and 1000 ppm) and one concentration of propylene (1300 ppm) applied for 24 hours on three different stages of maturity of ‘Opal Star’ and ‘Unique’ of feijoa suggests that ‘Unique’ and ‘Opal Star’ do not present typical climacteric activity. Feijoa fruit harvested at different stages of maturity were able to continue the ripening process without any acceleration by ethylene or propylene treatments. Different concentrations of exogenous ethylene or propylene had no effect on fruit firmness and colour changes. This could mean both cultivars are non-climacteric fruit according to the McMurchie et al., (1972) classification. However, this may also indicate that the fruit are already saturated with ethylene at early harvest stage. In ‘Unique’ highest ethylene production rates occur with early season fruit as they soften. Fruit at late harvest seems to be past the climacteric peak. In ‘Opal Star’ highest ethylene production occurred in late season, which may imply that climacteric peak happens at the ripe stage. There was no clear relationship between ethylene production and colour. This study supports the idea that the climacteric and non-climacteric classification is relatively general and unable to take into account the peculiarities of each species. In conclusion, this thesis offers important insights into the regulation of postharvest loss of quality in feijoa. These insights should allow the future development of non-destructive at harvest maturity tests for feijoa. In addition, CA storage conditions are defined that could be used to support sea freight of feijoa to distant markets, although it remains to be seen whether aroma fully recovers after CA.