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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 Surface pasteurisation of fresh chicken meat using UV-C technology : 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) Philip, Arthur JonathanFresh chicken meat is highly susceptible to contamination by spoilage and pathogenic microorganisms due to its high-water activity and rich nutrients. Following processing, aerobic mesophilic count (AMCs) on the surface of fresh chicken samples ranges from 3.00 to 4.00 log CFU/cm2. The New Zealand food safety guidelines stipulate that aerobic mesophilic counts (AMCs) present on surfaces of fresh chicken portion should be <6 log CFU/cm2 by end of shelf-life (6-7 days) when stored at 4°C. Hence, the safety and shelf-life of fresh chicken meat pose challenges for the industry. The UV-C technology, is a novel food processing technique that has lethal germicidal capability at 280-290 nm. Therefore, the technology has a potential to decontaminate suitable food products including the surfaces of fresh poultry portions. This study investigated the effect of UV-C light processing on untreated fresh skinless and skin-on chicken portions. The study was conducted in 2 phases to optimise the processing technology and determine its effects on fresh chicken samples during storage (4°C). One day old fresh chicken samples (skinless breast fillet, skinless thigh fillet, skin-on breast fillet, and skin-on thigh fillet) were obtained from a commercial processing factory and transported to Massey University, Auckland Campus, under chilled conditions (4°C) within an hour. In phase one, the fresh chicken samples were treated with four UV-C dosages (50, 100, 200, and 300 mJ/cm2) at ambient temperature (20°C) using a commercial UV disinfection system. AMCs were determined by swabbing the fresh chicken samples using swabs and 5-cm2 templates. Suitable dilutions (10-1 up to 10-6) of the swabbed samples were enumerated on standard plate agar with incubation at 30°C/72 h and grown colonies were expressed as log CFU/cm2. Temperature of the chicken samples before and after UV-C treatments was measured using a 20-cm probe thermometer. Treatment time was recorded automatically by the UV-C equipment. Phase one results showed that 50 mJ/cm2 was capable of maximum microbial reduction (skinless: 1.69 log CFU/cm2; skin-on: 0.21 log CFU/cm2) with minimal temperature changes (skinless: 3.14°C; skin-on: 3.32°C) and lowest exposure times (skinless: 2.17 minutes; skin-on: 2.22 minutes.). Therefore, 50 mJ/cm2 was selected as the optimum dosage for skin-on and skinless fresh chicken samples. In phase 2, the effect of optimised UV-C light dosage (50 mJ/cm2) on fresh chicken samples stored at 4°C/7 days was investigated. Instrumental color analysis, AMCs and lipid oxidation were determined at 4 different time points (day 0, 3, 5, 7) during storage (4°C). AMCs were analysed as previously described. The detection of E.coli, S. aureus, L. monocytogenes, Campylobacter spp. and Salmonella spp. were conducted at 0 and 7 days of storage using standard methods, while colour was measured by a colorimeter. Lipid oxidation was analysed by the thiobarbituric acid (TBA) method. Consumer sensory evaluation was carried out to evaluate raw and cooked chicken samples during storage. Raw chicken samples were evaluated by a focus group consisting of 5 semi-trained panelists at days 1, 5, and 7 while cooked samples were evaluated on days 1 and 7 by 30 panelists using a 9-scale hedonic test. For cooked chicken portions, samples were cooked to an internal temperature of 75°C using a convection oven. The cooked chicken samples were cooled to between 30 – 40°C before being served to the sensory panelists. The result of phase 2 showed that the initial mean AMCs were 3.31 ± 0.11 (skin-on) and 3.80 ± 0.35 (skinless) log CFU/cm2. After UV-C treatment, the AMCs of UV-treated chicken samples were reduced to 1.87 ± 0.98 (skinless) and 3.07 ± 0.34 (skin-on) log CFU/cm2, indicating that the AMCs for skinless and skin-on chicken samples decreased by 1.93 log and 0.24 log CFU/cm2 after UV-C (50 mJ/cm2) treatment, respectively. At the end of storage, the AMCs on skin-on chicken breast samples were 8.57 ± 0.34 (untreated) and 7.48 ± 0.07 (UV- treated) log CFU/cm2. Whereas, AMCs on skinless breast fillet were 8.62 ± 0.35 (untreated) and 6.73 ± 1.10 (UV-treated) log CFU/cm2, respectively. The results indicated that the growth of AMCs on untreated chicken samples exceeded the recommended limit on day 5, while UV-treated chicken samples were higher than the recommended limit on day 6 (skin- on) and day 7 (skinless). In addition, the AMCs results suggested that UV-C treatment was more effective on skinless chicken portion. Furthermore, pathogenic bacteria (E.coli, S. aureus, L. monocytogenes, Campylobacter spp., and Salmonella spp.) were not detected on untreated and UV-treated chicken samples on days 0 and 7 of storage, indicating the effectiveness of the chlorinated chilling processing step. Based on the Hunter L*, a*, b* colour readings and TBA (TBARS) results, the applied UV-C dose (50 mJ/cm2) had minimal impact on the color and lipid oxidation of both skin-on and skinless chicken samples during storage. However, a faint burnt odor was detected by sensory panelists during evaluation of UV-C treated fresh (raw) chicken samples stored (4°C) for day 1. The panelists did not detect any unpleasant odor from the cooked chicken samples during storage. Therefore, the results suggested that UV-C light may offer good prospects for shelf-life extension of fresh chicken samples. In addition, the results also indicated that UV-C light surface pasteurisation was more effective for skinless chicken samples, compared to its skin-on counterparts.Item UV radiation as a new tool to control microalgal bio-product yield and quality : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Industrial Biotechnology at Massey University, Palmerston North, New Zealand(Massey University, 2018) Schaap, RolandWhile ultraviolet (UV) radiation is most commonly known as an abiotic stress, various studies have shown targeted UV exposure increases bioproduct and biomass yields in microalgae. Microalgal cultivation processes face significant limitations in achievable bioproduct and biomass yields and thus improvements offered by targeted UV treatments during large-scale microalgae cultivation provide an opportunity for development of a novel UV treatment tool. Growing demand in microalgae (bio)products indicate there may be a substantial market for such UV treatment tools. No initiatives that explore the development of targeted UV treatments during large-scale microalgae cultivation have been found in the literature or in the industry. In collaboration with industrial partner BioLumic, a company specializing in applying targeted UV treatments in plants as a tool in agriculture, this PhD research examined if specific treatments of UV radiation (i.e. specific in UV waveband, irradiance and exposure duration) can reliably increase carotenoid accumulation in the microalga Dunaliella salina and if this new understanding can be feasibly used to develop an industrial system for UV treatment of microalgae. The PhD research was conducted utilizing D.salina after evaluation in four commercially relevant microalgae species: Arthrospira platensis, Chlorella vulgaris, Haematococcus pluvialis and D.salina. A UV-A induced carotenoid accumulated response was identified in D.salina (strain UTEX 1644). Targeted UV-A treatments reliably induced carotenoid accumulation in this species, and the magnitude of the response depended on the UV-A wavelength, UV irradiance, UV exposure duration, and UV dose. The UV-A carotenoid accumulation response was induced within 6 hours and was largely complete in 96 hours (24 h·d⁻¹ UV exposure). The highest UV-A dose tested induced the highest carotenoid accumulation rates and the highest total carotenoid concentrations after continuous UV exposure (24 h·d⁻¹) at the highest UV-A irradiance tested (30 W·m⁻²). Total carotenoid concentration increases of up to 162% were thus observed after 72 hr of UV-A exposure. UV-A exposure was associated with slowed or stopped cell proliferation as well as increased D.salina cell size (up to 15%) and altered intracellular structural organization. Carotenoid accumulation ceased and cell proliferation increased when UV-A exposure was stopped, leading to a subsequent resumption of cell proliferation. UV-A induced carotenoid accumulation was improved 51% during UV-A exposure concomitant with non-UV carotegenic stimuli (high PAR intensity and salinity) compared to UV-A exposure alone. The observations from experiments carried out in the thesis served as inputs in a techno-economic analysis (TEA) model developed to assess feasibility of large-scale UV treatment. The TEA model was developed to allow assessment of the most critical areas for improving profitability of large-scale UV treatment technology, rather than provide absolute economical outputs for revenue and profit. The TEA was based on two reference cultivation systems currently used for commercial D.salina cultivation. The TEA analysis considered four locations for the UV treatment system applied along the cultivation process: pre-cultivation stage (i.e. inoculum), main cultivation stage, post-cultivation stage (i.e. immediately prior to harvest) and during fluid transfer between stages. A dedicated post-cultivation UV treatment stage was shown to have a number of advantages over other treatment options. A model cultivation system for the case-study of D.salina was developed assuming an annual β-carotene production of 1,000 kg. The developed TEA model cultivation system and TEA UV treatment system were able to identify a potential increase in profitability generated from the application targeted UV treatment during large-scale D.salina cultivation. The maximum increase in profitability was achieved using a broad wavelength UV treatment system (irradiance = 30 W·m⁻², exposure duration = 24 h·d⁻¹, surface area coverage = 100%) applied during an intensive cultivation post-cultivation system. A relatively small contribution of the UV treatment system to CAPEX and OPEX to overall β-carotene production cost (i.e. < 10%) combined with the large increase in β-carotene production (711 kg·y⁻¹ and 895 kg·y⁻¹ for fluorescent UV tube and UV LED systems, respectively) leads to potentially large increases in profitability. The TEA analysis identified the magnitude of the UV-A induced carotenoid accumulation response to be the most important factor to influence the potential profitability. Moreover, the TEA indicated the increases in profitability are strongly influenced by optical efficiency, electrical efficiency and maximum optical power. The profitability estimates from the current TEA indicate that UV treatment during commercial microalgae cultivation has potential and justifies further research. To our knowledge the exploration of the fundamental UV photobiology in microalgae required to develop UV treatment regimes from discrete UV wavebands, complemented with a commercial microalgal-engineering insight, to produce UV treatment regimes and UV treatment technology for application during large-scale microalgae cultivation, has never been attempted. The multidisciplinary approach employed during this PhD research explored for the first time the development of a UV treatment system from laboratory observations to commercial cultivation. The current research described for the first time the UV exposure behaviour of D.salina (strain UTEX 1644) to varying UV waveband, UV irradiance, UV exposure durations as well as UV response interaction with PAR and salinity. The case-study of UV treatment during large-scale D.salina cultivation in this PhD research allowed recommendations to be made to the industrial partner BioLumic on potential areas of focus for continued research and development.Item Influence of solar ultraviolet-B radiation in New Zealand on white clover (Trifolium repens L.), ryegrass (Lolium perenne L.) and pea (Pisum sativum L.) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Agricultural Science at Massey University, Palmerston North, New Zealand(Massey University, 2002) Hofmann, AngelikaNew Zealand pasture plants have been exposed to increasing levels of ultraviolet-B radiation (UV-B) as a result of stratospheric ozone depletion during recent years. Thus far, there has been only limited published information on UV-B effects on pasture plants growing under field conditions. This study set out to investigate effects of natural solar UV-B radiation in the field for the pasture species white clover (Trifolium repens L.) and ryegrass (Lolium perenne L.) and compared those with pea (Pisum sativum L.), another economically important crop. Contrasting UV-B levels were created with two filter systems, using UV-B-absorbing glasshouse polythene film and UV-B-transmitting perspex glass. A further treatment included open plots that were not covered by filters. Ambient UV-B irradiance levels were recorded daily during the experimental period in summer from early December 1995 to late February 1996. The pasture species were investigated in monoculture as well as in their typical association in an established sward that was regularly grazed by sheep. Morphological measurements included leaf expansion, leaf initiation, leaf senescence, stem elongation, above-ground biomass and aspects of plant reproduction. To identify possible responses related to UV-B protection, measurements included specific leaf mass (SLM), accumulation of UV-absoibing compounds and of anthocyanins. The highest UV-B levels occurred during the early- and midsummer period from mid December to late January. Clouding reduced UV-B irradiance by more than 70%. The UV-B-absorbing treatment reduced ambient UV-B levels by about 90%, and the transmitting filters by about 25%. Results from the monoculture trials revealed interspecific differences in UV-B sensitivity between the three plant species tested. Ryegrass and white clover appeared UV-B-sensitive in a number of vegetative morphological aspects, while pea generally displayed UV-B tolerance. Most features of UV-B sensitivity in the two pasture species were recorded during midsummer in January, with young plant pans particularly affected by the UV-B-transmitting treatments. The area of young white clover leaves was reduced by about 20%, and the length of young internodes by more than 25%. Solar UV-B increased the number of senescing ryegrass leaves in January and induced white clover inflorescence formation in February. Inflorescence numbers were also increased in pea under UV-B-transmitting filters. While there was no clear relationship between SLM and UV-B susceptibility, the biochemical studies suggest that the interspecific differences in UV-B sensitivity may be due to differences in the accumulation of UV-absorbing compounds and of anthocyanins. Average levels of UV-absorbing compounds across treatments were about 50% higher in pea than in the two pasture species. Furthermore and in contrast to the pasture species, pea showed the highest levels of anthocyanins under solar UV-B in January. The results from the sward trials were in general agreement with the findings from the monoculture studies, showing that morphological sensitivity under the UV-B-transmitting treatments could also be detected for white clover and ryegrass when grown in association. This was reflected in a reduction of white clover leaf area and of leaf elongation in mature ryegrass tillers by 13%, and by more than 20% in young ryegrass tillers. The effects on the two species under pasture conditions were also reflected in whole sward measurements, showing decreases in sward height of about 15% and in herbage accumulation of about 20% under UV-B-transmitting filters. In conclusion, the findings from this study show that near-ambient solar UV-B levels can affect the morphology of the two most commonly sown pasture plant species in New Zealand. In contrast, pea showed tolerance to UV-B and this may at least be partly due to higher intrinsic levels of UV-absorbing compounds.Item Disinfestation of apple leaf-curling midge, Dasineura mali (Diptera: Cecidomyiidae) on post-harvest apple fruits by ultraviolet-C radiation : a thesis presented in partial fulfilment of the requirements for the degree of Master of AgriScience in Horticulture at Massey University, Palmerston North, New Zealand(Massey University, 2014) Yuan, DingApple leaf-curling midge (Dasineura mali Kieffer) (ALCM) is considered as an important quarantine pest of apple due to fresh fruit contamination by pupal cocoons. To meet the quarantine regulations of export markets and the expectations of customers, a series of non-chemical methods have been investigated for the potential to be applied to control insect pests. One approach, ultraviolet-C (UV-C) radiation, offers potential as a new disinfestation technique. However, the disinfestation effects of UV-C radiation in the control of ALCM have not been investigated previously. To investigate the disinfestation effect of UV-C radiation, two individual experiments were conducted. Apple fruit-attached and non-fruit attached cocoons of ALCM were treated with a series of UV-C radiation doses, and then maintained in temperature-controlled (daily mean temperature around 20 oC) dark conditions. For non-fruit attached cocoons, the groups treated with UV-C radiation had significantly higher mortality rates than that of the control groups. For fruit attached cocoons, although the sample size was small, results indicated that cocoons treated with 20 mins, which was the most prolonged UV-C radiation treatment, exhibited the highest mortality rate. The insignificant mortality rate of cocooned larvae when comparing those groups treated with lower UV-C doses and control groups suggests that attachment of cocoons to the apple calyx may be a significant factor in limiting the effect of UV-C for the control of ALCM. To obtain understanding of the effects of UV-C radiation on the potential fecundity of female ALCM, a third experiment was conducted, where adult insects were reared following UV-C treatment of cocoons as before, and egg numbers carried by newly emerged adult females were assessed. Interestingly, although the difference in the egg quantity of female adult ALCM between treatments was not significant, it revealed that the UV-C treated group had a potential higher egg capacity with increased body size than the control group. It is possible that the short duration of UV-C radiation treatments might lead to increased egg capacity of female ALCM, and these effects are worthy of future investigation. Equally, the possibilities to provide greatly increased UV-C doses to potentially kill ALCM cocooned larvae during apple processing should be explored further.Item Population studies of ultraviolet-B radiation responses in white clover (Trifolium repens L.) : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Biology at Massey University, Palmerston North, New Zealand(Massey University, 2000) Hofmann, Rainer W.; Hofmann, Rainer W.White clover growing in New Zealand is experiencing increasing levels of ultraviolet-B (UV-B) radiation as a result of ozone depletion. This thesis reports a series of investigations on morphological and physiological responses to UV-B in various white clover populations. In addition, these studies examined UV-B responsiveness in combination with drought and consequences for insect herbivores. Plants were grown in controlled environment rooms with and without supplemental UV-B radiation at a dose of 13.3 kJ m-2 d-1, corresponding to a 25% mid-summer ozone depletion above Palmerston North, New Zealand. Morphological measurements included numerous attributes of plant growth and morphogenesis as well as several aspects of leaf structure. Physiological studies investigated both primary and secondary metabolic functions. In general, UV-B reduced components of white clover growth. The white clover populations showed a number of constitutive and UV-B-induced differences in many morphological and physiological attributes. UV-B sensitivity was mitigated by drought and was less pronounced with increasing duration of UV-B exposure. Bioassays revealed differential dietary effects of UV-B-treated foliage on the performance of lepidopteran insects. UV-B effects were also apparent under frequent defoliation. Comparisons of morphological and physiological features showed that white clover UV-B responsiveness was mainly linked to inherent differences in morphology and growth among the populations, while on a physiological level it was more the UV-B-induced differences that conferred UV-B tolerance. In particular, UV-B tolerance of the white clover populations was related to lower constitutive productivity. This was further linked to several constitutive leaf attributes, including small leaf size, small and lens-shaped epidermal cells as well as low leaf water potential. UV-B-induced features linked to UV-B tolerance included high percentage of leaf dry mass, accumulation of UV-absorbing compounds and of total flavonols (particularly quercetin glycosides) as well as increases in leaf water potential. UV-B tolerance was greatest in white clover populations adapted to multiple and severe stresses in the habitat of origin. This series of investigations was used to propose a functional framework, linking UV-B responsiveness to underlying specialisation of the white clover populations.