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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 An integrated experimental and numerical approach to understand and address airflow and cooling variation in refrigerated shipping containers with kiwifruit pallets : 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. EMBARGOED until 16 December 2026.(Massey University, 2024-11-26) Alaka, AbdulquadriNew Zealand's kiwifruit industry has been the most significant contributor to the country’s horticultural export value for many years. Despite facing recent unseasonable weather conditions and labour shortage challenges, the kiwifruit industry contributed approximately 38.5 % to New Zealand's total horticultural export value in 2023. NZ kiwifruit and other horticultural produce earnings largely come from distant markets such as Europe, Japan and China, representing one of the longest supply chains in the world. NZ's expanding kiwifruit export volume heavily relies on refrigerated containers to preserve and maintain fruit quality along the supply chain. This is vital to ensure that the industry continues supplying its overseas customers with high-quality products and attracting significant export earnings. Refrigerated containers are designed to maintain cargo temperature throughout transit. However, sub-optimal airflow distribution inside containers when fully loaded with pallets of fruit often results in temperature variation within the cargo. Unfortunately, such temperature variation comes with a significant economic disadvantage as it results in fruit losses via chilling and, or freezing injury as well as senescence. It also leads to variations in the quality of fruit of the same batches, complicating inventory management along the supply chain. Improving the airflow distribution within stowed refrigerated containers can go a long way in improving temperature or cooling uniformity within the system. This project combined experimental and computational approaches to understand and improve airflow and cooling uniformity inside containers stowed with kiwifruit pallets.--Shortened abstractItem Model-based packaging design for minimising environmental impact of horticultural packaging systems : a thesis presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, New Zealand. EMBARGOED until 13 November 2026.(Massey University , 2024) Lozano, RaquelPackaging systems are instrumental in delivering high-quality food products to consumers. Food industries grapple with losses throughout the supply chain, resulting in both product and monetary setbacks. When considering the embodied resources in food production, including raw materials, energy, water, and emissions, minimising losses in any stage of the food supply chain is crucial. The New Zealand kiwifruit industry faces several constraints which include short harvest seasons, considerable distance to markets and year-round consumer demand. Packaging and storage plays a role in overcoming these factors by preventing undesirable quality loss traits. Establishing the link between packaging systems, supply chain conditions, and kiwifruit quality (specifically shrivel) provides a basis for evaluating the trade-off between over-packaging and excessing fruit loss. In this thesis, an integrated-mathematical model was developed to aid decision-making in for kiwifruit packaging, aiming to minimise the overall environmental impact throughout the kiwifruit supply chains from packhouse to purchase. This integrated-mathematical model facilitates exploratory analysis of both current and future supply chains and packaging systems. Four models were integrated: mass balance, moisture loss prediction, shrivel loss prediction and an optimisation engine. The mass balance model captured the kiwifruit and packaging masses and associated environmental impacts within kiwifruit supply chains. This model, applicable to any environmental metric, was developed to facilitate the prediction of kiwifruit losses. To validate its accuracy, the framework was applied in assessment examples, comparing its performance against existing research for kiwifruit supply chains. The absolute difference between predicted and actual emissions of CO2eq were less than 1% of the actual mean emissions at different stages of the supply chain. The moisture loss model was used to estimate kiwifruit weight loss both on a packaging unit and individual kiwifruit basis. The model demonstrated close agreement between weight loss predictions and experimental data for average packaging weight loss scenarios. Further refinement is needed to predict individual kiwifruit weight loss, specifically considering the impacts of packaging features on internal packaging water vapour distributions. The shrivel prediction model revealed that predicting kiwifruit losses due to shrivel posed challenges, primarily due to the current knowledge gap regarding the development of shrivel in kiwifruit under storage conditions. While increases in shrivel has been correlated to weight loss in existing literature, the reference state (at orchard, packhouse etc.) is arbitrary. Ideally shrivel would be related to an intrinsic property that could be measured at any point in time without requiring knowledge of this prior history of the fruit. The prediction of losses based on a non-relative starting point represents a knowledge gap addressed in this work, with potential improvements identified for future model iterations. This phase of the model development heavily relied on data collection to establish a mathematical relationship between weight loss and shrivel. The moisture loss and shrivel model served as the foundation for the development of an optimisation engine, enabling the identification of the optimal use of packaging. This model sought a balance between packaging mass and kiwifruit losses, employing various environmental impact categories as performance metrics. The success of this approach was evident as optimal packaging points were identified across (i) different packaging materials, (ii) different packaging materials and formats and (iii) different environmental impact categories. It was found that each optimum point for materials were unique to the ambient conditions of the supply chain, packaging format and material. This work revealed trade-offs between the environmental impact of the packaging material and amount of kiwifruit loss, numerically demonstrating what so far has only been presented as a theoretical concept in other research. Then, this integrated-model was applied to a range of real-life supply chain scenarios showcasing its versatility in addressing possible questions such as ‘what if ?’, ‘can we ?’ and ‘when can we ?. The application of the model to real-life scenarios demonstrated its utility for decision-making with respect to packaging materials and formats. This model is poised to offer crucial support for future packaging materials and supply chains. The limitation of this model lies in fruit loss predictions. To further model applicability, there remains further investigation of hypotheses developed during shrivel model development to refine the kiwifruit loss model. There also remains the opportunity to integrate more prediction models that account for the impact of packaging on other drivers of fruit loss, such as ethylene concentrations within the pack. While the integrated model developed in this thesis has some limitations in accurately predicting kiwifruit losses, this study highlights the significance of linking packaging performance and kiwifruit quality when evaluating environmental impacts. Although kiwifruit served as the focus in this work, the model created here paves the way for exploring the application of optimised packaging systems for other food commodities.Item Application of UV-C technology in extending the shelf life of fresh blueberries : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology at Massey University, Albany, New Zealand. EMBARGOED until 1st August 2027(Massey University, 2024) Akram, SidraFresh blueberry fruit is highly perishable and susceptible to spoilage by bacteria and fungi resulting in a short postharvest shelf life. Ultraviolet light treatment (UV-C) in the range is considered an emerging novel food processing technique that can be used to improve fruit quality and thus prolong the shelf life. The study investigated the impact of UV-C light treatment on untreated fresh blueberry farthing variety. The study was conducted in three phases to analyse and optimize the most suitable dosages to be applied to the sample and determine its effects on the fruit sample during the 14 days of storage at 4°C. The fruit sample was collected from a local blueberry farm and transported to the Massey University, Auckland campus. In phase one, the fresh blueberry fruit was treated with different dosages of UV-C (50, 100, 200, 300, 400, 600 mJ/cm²) using a JouleSafe disinfection system. Focus group sensory evaluation was used to analyse the consumer acceptance of the UV-C treated fruit alongside the microbial enumeration to narrow down the range of dosages.--Shortened abstract.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 Sustainable food packaging : potential of using fibres from hemp hurd for thermoformed moulded pulp food packaging : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology, Massey University, Auckland, New Zealand. EMBARGOED until 20 July 2026.(Massey University, 2021) Lo, Chi HouThere is currently high demand for sustainable packaging solutions, and also for new, sustainable fibre sources beyond traditional wood-based options. The aim of the work in this thesis was to evaluate whether hemp hurd fibre, a low value waste stream from the hemp industry, could be used to manufacture moulded pulp trays for food serviceware as a replacement for the single use plastic tray currently used. The hemp hurd was pulped and mixed in varying ratios with pine pulp to form handsheets. The handsheets were treated using different thermoforming conditions and the resulting performance determined. Handsheets based on mechanically pulped pine fibre and chemically pulped hemp hurd fibres were investigated, and characterised by several tests including tensile, tearing, bursting, short-span compression, ring crush, Gurley, contact angle and Cobb testing. The handsheets made from hemp hurd had promising mechanical properties and barrier performance compared to mechanically pulped pine fibres which were chosen to represent the relatively cheap pine pulps used in moulded fibre products industrially. This difference in performance is because the collapsed fibres in chemically pulped hemp hurd resulted in larger bonded areas.--Shortened abstractItem 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.
