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Item Mathematical modelling of airflow during forced draft precooling operations : 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, 2024-11-01) Tapia Zapata, Nicolas IgnacioBy the year 2020, the kiwifruit industry represents approximately 37 % of the horticultural export industry sector in New Zealand. Thereof, the kiwifruit cold chain aim is to reduce losses due to poor temperature control and energy usage during refrigeration. By forced convection aided by fans in palletised kiwifruit, field heat is removed rapidly prior to storage, thus optimising shelflife of the produce. Previous Computer Fluid Dynamics (CFD) model determined the optimal operating point for palletised kiwifruit during forced-draft cooling. However, CFD requires complex simulation, in detriment to computational efficiency and solving time. Therefore, there is an imperative to provide innovative tools that optimise package design by iterating several designs and that is applicable to the local industry sector for cold chain optimisation. In this spirit, this projects aimed to development of a simplified approach for the prediction of airflow distribution of palletised kiwifruit during forced-draft cooling, that can be coupled with an alternative heat transfer model, thus providing a fast and robust package optimisation routine that can inform cooling performance of several package design and pallet configuration.Item Does the in-packaging food preservation technique, retorting, affect the migration of food packaging? : a thesis presented in partial fulfilment of the requirements for the degree of Master of Engineering in Chemical Bioprocess Engineer at Massey University, New Zealand(Massey University, 2024) Spencer, Hannah JoyThe effects of retort treatments on chosen monolayer plastic films commonly used in the food industry were studied. Changes occurring in the plastic monolayers and the leachates into the food system, and post-retort treatments were monitored. Three industry-relevant retort settings were trialled: 110 °C for 51 mins, 115 °C for 25 mins, and 121 °C for 16 mins. The monolayer plastic films studied were polyethylene, polyethylene terephthalate, and polyamide; common components of multi-layer retort pouches. The key areas for this research project were to investigate how different retort time-temperature profiles affect the monolayer physically and the overall and specific migration from monolayer films into different food simulants. This was used to determine whether a significant change in migration from the monolayer films was associated with retort processing. The plastic was tested using EU standards of compliance and using 10 % ethanol and 3 % acetic acid as food simulants to represent retort products. The materials were visually inspected straight after retorting, followed by an in-depth internal surface investigation to monitor changes via microscopy. The overall and specific migration was assessed, and compounds putatively identified were assigned a Cramer class. Overall, the retort treatment at 110° C for 51 mins created the most changes in terms of migration on most of the samples. The results of this research were for the simulants: ethanol triggered significantly more changes in PE and PET. For PA films the results revealed that both simulants had a similar number of changes, due to long processing time.Item Effect of UV-C treatment on sanitised and unsanitised ready-to-eat leafy green vegetables, produced in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology, Massey University, Albany Campus, New Zealand(Massey University, 2023) Abthiyar, LovinaSeveral outbreaks in ready-to-eat (RTE) salads have been reported with major concerns comprising of enteric pathogens such as Coliforms, Listeria (L.) monocytogenes and Salmonella spp. that have fast growth rates and low infectious doses. To improve the microbial safety of RTE salads, various methods have been used including non-thermal ultraviolet (UV) irradiation. Non-thermal UV irradiation causes fewer changes in the nutrition and sensory quality of food, compared to the conventional methods. This study investigated the effect of non-thermal UV-C dosage on microbiological levels of fresh commercial samples of sanitised (n=4) and unsanitised (n=4) spinach, kale, rocket and mesclun using 100 mJ/cm² dosage including controls. A commercial company in New Zealand supplied eight (n=8) freshly prepared commercial and packaged RTE salad samples. The sanitised samples had undergone normal preparation steps which included cutting, washing, and sanitation. The packaged samples (n = 8) were transported under chilled conditions (4°C) to Massey University Auckland Campus. Upon delivery, the samples were coded and treated by irradiation at 100 mJ/cm² (Radiant UV-21A0043, International Light Technologies, Inc. USA). The control and test (treated) samples were re-packaged in heat-sealed micro-perforated bags and stored for 12 days/4°C. Sample packages were retrieved on days 0, 4, 8 and 12 for analysis of total aerobic mesophilic counts (AMC), Coliforms, L. monocytogenes, S. aureus and Salmonella spp. using standard methods. The weight and colour (Minolta, Japan) of the samples were measured as well as evaluated by a focus sensory group for colour, texture, flavour, juiciness, firmness and aroma. UV-C treatment (100 mJ/cm²) successfully reduced total AMC in all the sanitised and unsanitised salad samples (n=8) and no pathogens were detected during storage for 12 days/4°C. During storage, the AMC increased (p0.05) on the AMC. Kale samples recorded lower AMC for the irradiated samples (p<0.05). UV-C treatment of salads increased the lightness L* for all the samples except for rocket, decreased the yellowness b* for spinach and kale samples and did not affect the greenness a* of the salads. The lightness L* was lower (p0.05) on the greenness a* of spinach, kale, mesclun and rocket samples. The yellowness b* of spinach and kale was significantly affected by the dosage and the storage period (p0.05) on the b* value. Sanitization had a significant effect on the rocket samples (p<0.05) as sanitised rocket had a lower b* value than the unsanitised rocket. The effect of UV-C treatment on the weight loss (%) of salad samples was different for each salad. The weight loss (%) was higher in UV-treated spinach and kale samples than in the respective controls. Mesclun samples had the highest weight loss for control samples than UV-treated samples. For rocket salads, unsanitised controls (non-UV-treated) had higher weight loss than the unsanitised treated sample and the sanitised treated sample had slightly higher weight loss than the sanitised control sample. Focus group sensory evaluation indicated that UV-treated salads had better taste than control samples, although the appearance, texture and colour were poorer than the non-UV-treated samples. Overall, UV treatment reduced AMC in RTE salads without affecting the taste of the vegetables for 12 days/4°C. However, more work is required to maintain the overall appearance and texture of UV-treated salads.Item Degradation of aflatoxin M1 in skim milk using UVC or cold plasma : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology, the School of Food and Advanced Technology, Massey University, Manawatu, New Zealand(Massey University, 2021) Nguyen, Thi ThuContamination of aflatoxin M1 (AFM1) in milk and milk products has been an issue for decades as it is a food safety risk, classified as a Group 1 carcinogen. Cows consuming feed contaminated with fungi (Aspergillus flavus and Aspergillus parasiticus) that produce aflatoxin B1 (AFB1), convert AFB1 to AFM1 that is released into the milk. The best way of controlling AFM1 contamination in milk is to keep the feed dry to prevent the growth of fungi to avoid the production of AFB1. However, this is challenging in some tropical countries where the weather is hot and humid all year around. Treating milk contaminated with AFM1 is an alternative method of control. The aim of this study was to investigate two methods for milk treatment - UVC and cold plasma to reduce AFM1 in milk, investigate the factors influencing these treatments and identify the degradation products after treatment. UVC (254 nm) reduced AFM1 in skim milk to below MRL (0.5 μg/L) from an initial level of 1 μg/L after 20 min treatment. Treatment time (min), depth of samples (mm) and the stirring of the milk sample during treatment were found to significantly (P < 0.05) enhance the reduction of AFM1 in milk. The contamination level (μg/L) and fat content in milk did not significantly (P > 0.05) effect the UVC efficacy. A change in milk colour was observed but the pH of the milk samples did not change. The degradant of AFM1 after UVC treatment was identified as an oxidation product which resulted in hydroxylation occurring at the double bond of the furan ring of AFM1 molecules. High voltage atmospheric cold plasma (HVACP) was used to reduce AFM1 in skim milk and explore the effect of treatment times (5, 10 and 20 min), operating gases (air and MA65 - 65% O2, 30% CO2, 5% N2), three voltages (60, 70 and 80 kV), using direct and indirect treatment, AFM1 contamination levels (0.1; 1 and 50 μg/L) and the volume of the sample (10, 20 and 30 mL). A reduction of 64.99 and 78.86% of AFM1 in skim milk after 20 min HVACP treatment using air and MA65, respectively, was achieved with the initial level of 1 μg/L. HVACP did not change the milk colour after 20 min treatment but a slight change in pH was observed. Different treatment times, different operating gases and voltages, direct and indirect treatments were found to have the most effect on AFM1 reduction. While AFM1 contamination levels (0.1; 1 and 50 μg/L) had an insignificant (P > 0.05) effect on AFM1 reduction in milk. A dielectric barrier discharge (DBD) cold plasma set up with small capacity high voltage generator was used to investigate the effects of other operating gases with different mixtures (5, 10 and 20% of air, pure oxygen and nitrogen in helium) and the effect of milk components (casein, lactose and whey protein) on AFM1 reduction. The degradation products of AFM1 after cold plasma treatment were determined. Although this small capability system reduced approximately 70-100% of AFM1 in water after 3 and 10 min treatment by using air/helium (10/90), the reduction of AFM1 in skim milk, whey and casein was much less, although 70% of AFM1 was reduced in lactose. The reduction of AFM1 in water was significantly (P < 0.05) improved by cold plasma with the increase in the concentration of air/pure oxygen in helium but it was unchanged regardless of the ratio of nitrogen in helium. The structure of three degradants of AFM1 after cold plasma treatment was elucidated with the confirmation of two of them resulting from damage to the furan ring of AFM1 molecules. The structure of the third one was proposed but another analysis technique is required to confirm.Item Does cold shock treatment extend the shelf life of avocado fruit? : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Palmerston North, New Zealand(Massey University, 2020) Vo, Dong HoaiAvocado ripens rapidly after harvest causing the difficulty for fruit export to distant markets. Cold storage at 4 – 6 °C is the most popular method to extend the shelf-life of avocado for 4 weeks. Chen et al. (2017) showed that cold shock treatment (CST) at 0 °C for 30 mins effectively delayed ripening-associated processes, reduced respiration rate, ethylene production and cell-wall enzyme activities. The objective of this thesis was to provide better insight into the effects of CST on delaying avocado ripening by observing the influence of CST on post-storage qualities of avocado. The experiments replicated the experimental work of Chen et al. (2017). Experiment 1 was to identify the suitable CST in a full matrix of three temperatures (0, 2 and 4 °C) and six durations (15, 30, 45, 60, 90 and 120 minutes). The effects of CST were not observed on firmness retention measured by puncture test, however, there was a consistent trend that colder temperatures and shorter treatments resulted in better firmness outcomes although there are not statistically significant, possibly due to the large fruit variability. Experiment 2 was to replicate the experiment 1 with increased sample size to 3 times to reduce the influence of fruit to fruit variation on the data analysis. The effects of CST on firmness retention were not seen. The large fruit variability still remained the big issue. Experiment 3 was designed to increase the sample size to 10 times compared to the previous experiment to minimise the large fruit variability using a selected single treatment (0 °C and 60 minutes). The effect of CST treatment on the ripening (including pulp softening, skin discolouration, respiration rate and ethylene production rate) was not statistically significant, however, the considerable reduction of ethylene production rate was observed. Experiment 4 was designed to provide better insight about the effects of CST on the overall qualities of avocado using 2 different methods for firmness measurements (destructive and non-destructive method). The effects of CST on the ripening was insignificant, however, ethylene production rate significantly reduced with treated fruit. Nevertheless, unlike the experiment results of Chen et al. (2017), in the current study, CST was not found to have any pronounced effects on fruit quality through 4 experiments.Item Microencapsulation of Lactobacillus reuteri DPC16 using spray-drying : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Auckland, New Zealand(Massey University, 2020) Wang, FangProbiotic microorganisms and the products containing the beneficial microorganisms are popular due to their ability to confer health benefits on consumer health. The majority of probiotics are delivered in liquid media which limit their shelf life and they are not convenient for the modern lifestyles. Thus, in this study, different wall materials for the microencapsulation of Lactobacillus (L.) reuteri DPC16 were investigated in Stage 1. The shelf-life tests of selected spray-dried powders were carried out in Stage 2 with different packaging materials. In Stage 1, L. reuteri DPC16 was encapsulated in 10% reconstituted skim milk (RSM), 10% gum Arabic, 10% maltodextrin, and 4:1 mixed wall material (2.5% whey protein isolate/ 2.5% gum Arabic/ 2.5% inulin/ 2.5% sucrose), (w/w) then spray-dried at 160 ℃/80 ℃ inlet/outlet temperatures. The spray-dried DPC16 microcapsules were characterised for viable cells of the probiotic, water activity and morphology. Viable cell counts were measured using standard plate count method, water activity using a water activity meter (AquaLab, Series 3, New Zealand) and the morphology of the powder particles was scanned by the electron microscope (FEI Electron Optics, Quanta 200, The Netherlands). Results of Stage 1 showed that at the inlet/outlet temperatures of 160 ℃/80 ℃, the RSM as an encapsulation wall material had the highest cell counts (98.06%±0.86%) with 0.284±0.005, water activity followed by the mixed wall material which contained cells of 93.97%±1.49% log CFU/g with water activity of 0.196±0.010. The powder made from gum Arabic had the lowest viable cells (90.63%±3.08%) with 0.170±0.005, water activity. Thus, RSM showed good potential to maintain high cell viability during spray-drying although the water activity was higher than the expected range of <0.25. For all the treatments, particle sizes of the powders were well below 100 μm which is ideal for addition to food products as they do not affect mouthfeel. Most of the powder particles were spherical with variable sizes and dented surfaces. Thus, RSM and the mixed wall materials were selected for encapsulating DPC16 in the storage trials. In stage 2, DPC16 were encapsulated using selected wall materials (RSM and the mixed wall material) and vacuum-packed in PET/EVOH/PE co-ex topweb FOC films (Multivac New Zealand Ltd) and aluminium foil bags (ALFW5-18, PBAG, China), then stored at 25 ℃ and 55 ℃ for four weeks. During storage, viable cells of the DPC16, water activity, colour, moisture content, and morphology of the powder were determined. Colour was measured by the Minolta Colourimeter (Minolta, Japan), moisture content was determined by the oven-dry method, bulk density was determined by the measuring cylinder method and the other characteristics of the powders were determined as previously described. The survival of DPC16 cells encapsulated in skim milk and vacuum-packed in aluminium bags were higher and more stable during storage at 25 ℃. Water activity, moisture content, bulk density, colour and morphology of the powder were all relatively more stable than in other treatments. Water activity (mean) and moisture content (mean) were within the expected ranges for the product. When stored at 55 ℃, the viable cell counts of DPC16 encapsulated in RSM and vacuum-packed powder in PET/EVOJ/PE co-ex topweb FOC film decreased to <106 CFU/g by end storage which was below the FAO/WHO, 2003 recommended level. The moisture content (0.0246±0.0003) was also below recommended levels (0.028 – 0.056), although water activity (0.102±0.007) was within expected levels (<0.25). Low moisture levels are critically important for the survival of encapsulated spray-dried probiotic microorganisms. High moisture initiates chemical reactions within the carrier materials leading to cell death and also affects colour stability. However, storage temperature is also important to cell survival. In conclusion, the present study showed that spray-drying encapsulated L. reuteri DPC16 in 10% RSM at 160°C/80°C, followed by vacuum-packaging in aluminium bags showed potential to maintain cell viability during storage (25 °C) for four weeks. It is desirable to check the performance of the encapsulated DPC16 powders in the simulated gastrointestinal tract and its ability to target-release the cells in the colon.Item An exploratory analysis of the factors impacting on Chinese consumer trust in lactic acid bacteria preserved beef and its mediation impact on purchase intention : a thesis presented in partial fulfillment of the requirement of the degree Masters in Agricommerce, Massey University, Palmerston North, New Zealand(Massey University, 2019) Chen, JinyaEvery year, worldwide, millions of people die and many are hospitalized due to food-borne diseases and illnesses caused by the consumption of contaminated food. Food safety has continued to be a concern for consumers, the food industry, and regulatory agencies. In China, there is almost a constant stream of reports about various food safety issues. Chinese consumers are concerned about the need for healthier and safer food. The development of science has provided more opportunities and possibilities to change the way we live. However, consumers’ overall confidence in Chinese food is not high and they are increasingly skeptical about new food. This research focuses on a new and not yet launched biological food, Lactic Acid Bacteria preserved vacuum-sealed chilled beef (LAB beef), as an example to examine what factors would have a significant correlation with consumers’ trust in this product and to examine if trust is the key factor impacting on consumers’ purchase intention. In order to complete the study objectives, a self-completed social survey was conducted in Shanghai City and Chengdu City, totaling 514 respondents. The analysis methods used included a measure of correlation, Gamma, principal component analysis and structural equation modeling. SPSS, Excel and Amos software were used. One outcome of this research was the finding that a number of socio-demographic factors were not strongly correlated with consumer trust in LAB beef, unlike some previous research that found such relationships with trust in new food technologies. Personal beef consumption habits, consumers’ past purchase experience with current used beef, products, product knowledge and food safety concerns based on their awareness, experience and media exposure were found to be important in establishing trust in LAB beef. The second outcome of this research is the confirmation of the importance of trust in determining consumers’ willingness to buy LAB beef, as well as the confirmation of the mediation effect of trust in explaining the underlying causal relationship between a number of independent variables and the dependent variable, willingness to buy.Item The signal-based microbial spoilage on New Zealand export lamb : thesis submitted to Massey University for the degree of Doctor of Philosophy(Massey University, 2019) Zhang, YufengLamb is one of New Zealand’s primary exports; however, the spoilage of lamb causes considerable financial loss. Psychrotolerant, anaerobically growing spoilage bacteria are responsible for the spoilage of fresh chilled vacuum-packaged lamb exported from New Zealand. These spoilage bacteria interact with through a system called “quorum sensing”. Different types of quorum sensing signals are produced by spoilage bacteria in response to the bacterial cell population. Through this cell-to-cell interaction, the expression of certain genes is regulated, followed by changes in bacterial activity. The main objective of this research was to determine the influence of quorum sensing signals produced by those psychrotolerant, anaerobically growing spoilage bacteria on the spoilage of New Zealand lamb. Quorum sensing of psychrotolerant, anaerobically growing spoilage bacteria was studied using in vitro and ex vivo methods. Two types of in vitro quorum sensing signals (Type-I and Type-II) were identified for New Zealand reference type strains Hafnia alvei and Serratia liquefaciens, and Type-II quorum sensing signal was found from a lamb isolate Carnobacterium divergens. These two types of signals were also discovered in spoiled chilled vacuum-packed lamb. After random EZ-Tn5 transposon mutagenesis to luxI/R-type genes and luxS genes, which are responsible for Type-I and Type-II signals respectively in H. alvei, S. liquefaciens, and C. divergens, wild type and mutant strains were compared. Type-I quorum sensing signaling molecules influenced the expression of lipB that regulates the secretion of hydrolytic enzymes produced by H. alvei and S. liquefaciens. These enzymes are believed to contribute to lamb spoilage. Cinnamaldehyde added to fresh vacuum-packed New Zealand lamb as an inhibitor of quorum sensing enabled an extension of the shelf-life of lamb by 2-8 days, through deactivating the Type-I quorum sensing system. Inhibition of quorum sensing has the potential in lamb preservation.Item 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 KwambokaExport 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.Item Characterising texture and cellular level responses of 'Centurion' blueberries during storage in different weight loss conditions : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Albany, New Zealand(Massey University, 2019) Franklin, Deena KelseyPostharvest blueberry softening hinders consumer acceptance and correlates with high moisture loss during storage. Such textural variations have been attributed to factors such as turgor, cell wall modifications and other microstructural changes in the outer cell layers of the fruit. This thesis investigated the impact of moisture loss on blueberry quality, as well as the structure/function relationships associated with fruit texture characteristics during postharvest using an integrated physical and microstructural approach. Four different weight loss conditions (62%, 76%, 93% and 98% RH) were evaluated over a three week postharvest storage period to assess blueberry texture parameters using a texture analyser, where microstructural changes were assessed by light microscopy and optical coherence tomography (OCT). Under high weight loss conditions there was an increase in berry softening and a decrease in texture characteristics whereas an increase in berry firmness, hardness and gumminess was observed during storage under low weight loss conditions. Light microscopy clearly illustrated microstructural differences among ‘Centurion’ blueberries stored in different weight loss conditions, in retention of cell shape, degree of cell to cell wall contact, the amount of space between cells and cell wall integrity. When berries lost moisture during storage, epidermal and subepidermal cells retained their integrity, and parenchyma cells lost integrity leading to collapse which may contribute to overall fruit quality during postharvest. 3D OCT images showed no obvious differentiation between large cells at each weight loss treatment, however significant differences were observed in the microstructure between each storage period. In general the microstructure of medium to large cells in the parenchyma tissue showed an increase in average surface area and total surface area after each storage period. In summary, low weight loss storage conditions help to preserve blueberry texture and quality, whilst maintaining cellular structure and integrity during postharvest storage. It is recommended blueberries are stored between 95 – 99% RH and at a low temperatures to prevent moisture loss during postharvest.