The validation and potential use of mathematical models to estimate the shelf-life of refrigerated food exposed to temperature abuse and basing such estimations on microbial growth was analyzed. Combined heat transfer, microbial growth models, and non-parametric statistical procedures formed a computer-based predictive tool to assess shelf-life and estimate the accuracy of the prediction. Experiments were carried out to assess the precision of the combined model parameters. The different situations analyzed considered stepwise fluctuations in environmental temperature and a change in package characteristic (size and packaging material). Computer simulations showed that even when the temperature abuse period constitutes a small fraction of the total exposure time (2%-3%), shelf-life can be highly affected (20%-30%). To analyze the precision of the combined model response, two sources of variation were considered, microbial growth and heat transfer parameters. First order, pseudo-zero order kinetics and Arrhenius model formed the basis for the microbial model. The accuracy of lag and exponential phase of microbial growth for a mixture of three microorganisms (P. fluorescens, S. aureus, and A. Iwoffi) was assessed using a nonparametric statistical procedure based on the bootstrap method. The activation energy (E [subscript a]) and the logarithm of the frequency factor (InK₀) were found to be 109±3.4 J/mole and 48.3±1.5 for the exponential phase of this microbial mixture. The values for the exponential phase were 152±4 J/mole and 64.0±1.7, respectively. These parameters together with experimental values for the overall heat transfer coefficient were used to analyze the precision of the model response. This precision was not affected by a change in environmental temperature and packaging characteristics and remained constant at ±1 day. Two different temperature abuse situations yield estimated shelf-life of 4.8±1 and 8.9±1 day, respectively. This result can not be generalized as it depends on the particular examples analyzed. / Graduation date: 1993

Please read the abstract in the 00front part of this document / Dissertation (MSc (Food Science))--University of Pretoria, 2007. / Food Science / unrestricted

Shelf life is a parameter of the lifetime distribution of a food product, usually the time until a specified proportion (1-50%) of the product has spoiled according to taste. The data used to estimate shelf life typically come from a planned experiment with sampled food items observed at specified times. The observation times are usually selected adaptively using ‘staggered sampling.’ Ad-hoc methods based on linear regression have been recommended to estimate shelf life. However, other methods based on maximizing a likelihood (MLE) have been proposed, studied, and used. Both methods assume the Weibull distribution. The observed lifetimes in shelf life studies are censored, a fact that the ad-hoc methods largely ignore. One purpose of this project is to compare the statistical properties of the ad-hoc estimators and the maximum likelihood estimator. The simulation study showed that the MLE methods have higher coverage than the regression methods, better asymptotic properties in regards to bias, and have lower median squared errors (mese) values, especially when shelf life is defined by smaller percentiles. Thus, they should be used in practice. A genetic algorithm (Hamada et al. 2001) was used to find near-optimal sampling designs. This was successfully programmed for general shelf life estimation. The genetic algorithm generally produced designs that had much smaller median squared errors than the staggered design that is used commonly in practice. These designs were radically different than the standard designs. Thus, the genetic algorithm may be used to plan studies in the future that have good estimation properties.

Orientador: Benedito Carlos Benedetti / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agricola / Made available in DSpace on 2018-08-15T14:30:00Z (GMT). No. of bitstreams: 1 Amaral_RiviaDarlaAlvares_M.pdf: 2125836 bytes, checksum: b3ba028f24bb9878b2ec5bdd1f757773 (MD5) Previous issue date: 2010 / Resumo: O sucesso comercial dos produtos minimamente processados depende da manutenção do seu estado fresco, retardando ao máximo a perda de qualidade nutricional. Esses produtos devem ser microbiologicamente seguros e ter vida útil suficiente para tornar viável o seu consumo pelos consumidores. O método mais usado no Brasil para sanitização de frutas e hortaliças minimamente processadas é o químico, por meio de solução com hipoclorito de sódio, mas devido à produção de compostos orgânicos clorados e seu potencial carcinogênico, tem ocorrido a busca por alternativas a esse sanitizante. Duas possibilidades são os métodos físicos água ozonizada e radiação UV-C. Assim, esse trabalho teve como objetivo avaliar estes sanitizantes como possíveis substituintes ao hipoclorito de sódio e foi dividido em duas fases. Na primeira foram definidas as concentrações mais adequadas de água ozonizada e radiação UV-C, além da embalagem para serem usados na segunda fase. Nesta, comparou-se os tratamentos água ozonizada (1,6 mg L-1/1 min), radiação UV-C (11,3 kJ m-2) e hipoclorito de sódio (100 mg L-1/1 min) e água corrente. Melões amarelos previamente resfriados foram minimamente processados passando por seleção, caracterização inicial, lavagem em água corrente, drenagem, corte em fatias com retirada das sementes e cascas, sanitização, drenagem, acondicionamento e armazenagem a 5 ºC ± 2 ºC por 10 dias. Os produtos foram analisados logo após o corte, após a sanitização e aos 3, 6, 8 e 10 dias de armazenamento quanto a análises físico-químicas e microbiológicas. A concentração de água ozonizada e intensidade de radiação UV-C mais efetivas na redução microbiana de melão amarelo minimamente processado foram de 1,6 mg L-1/1 minuto e 11,3 kJ m-2, respectivamente. A maior modificação da atmosfera ocorreu nas fatias embaladas com PEBD, alcançando concentrações de 15,66% e 2,43% de O2 e CO2, respectivamente, no nono dia de armazenamento. Tanto a água ozonizada quanto a radiação UV-C foram eficientes na redução da carga microbiana do melão minimamente processado armazenado a 5 ± 2 ºC por 8 dias e podem ser substitutos do hipoclorito de sódio. Os sanitizantes avaliados não comprometeram a qualidade físico-química dos melões minimamente processados / Abstract:The commercial success of minimally processed products depends on the maintenance of fresh state, avoiding the loss of nutritional quality. These products must be microbiologically safe and an enough shelf life to make feasible its use by consumers. The method most used in Brazil to sanitize fruits and vegetables is the chemical, with a solution of sodium hypochlorite, but due the production of chlorinated organic compounds and its carcinogenic potential, has been occurring the search for alternatives methods. Two possibilities are the physical methods ozonated water and UV-C radiation. Thus, this study aimed to evaluate these sanitizers as possible substitutes for sodium hypochlorite and was divided into two phases. In the first set the concentrations of ozonated water (1,6 mg L-1 , 1,8 mg L-1 and 2,0 mg L-1), UV-C radiation (4,80 kJ m-2 and 11,3 kJ m-2) and packaging (PP, LDPE and PET) to be used in the second phase were defined. In this, it was compared the treatments ozonated water (1,6 mg L-1/1 min), UV-C radiation (11,3 kJ m-2) and sodium hypochlorite (100 mg L-1/1 min) and water. Cooled yellow melons were minimally processed through selection, initial characterization, washing in water, draining, cut into slices, sanitization, drainage (1 minute), packaging and storing at 5 ºC ± 2 ºC for 10 days. The products were analyzed immediately after cutting and at 3, 6, 8 and 10 days of storage on the physical-chemical and microbiological analysis. The concentration of ozonated water and intensity of UV-C radiation more effective in the microbial reduction of fresh-cut melon were 1,6 mg L-1 for 1 minute and 11,3 kJ m-2, respectively. Slices put in PET packages remained the gas composition similar to the atmospheric air, showing that this package is not suitable when the atmospheric modification is required. The higher atmosphere reduction was in slices packaged in LDPE, reaching concentrations of 15,66% and 2,43% of O2 and CO2, respectively, on the nine day of storage. Both UV-C radiation and ozonated water were effecitve in reducing microbial load of fresh-cut melons stored at 5 ºC ± 2 ºC for 8 days and can be substitutes for sodium hypochlorite. The sanitizers evaluated did not affect thephysical-chemical quality of fresh-cut melons / Mestrado / Tecnologia Pós-Colheita / Mestre em Engenharia Agrícola

Thesis (Ph.D.(Microbiology)) -- University of Limpopo, 2022 / Traditional sorghum juice is produced in many African countries for human consumption. The juice is very rich in calories, B-group vitamins including thiamine, folic acid, riboflavin, nicotinic acid, and essential amino acids such as lysine. Low earning income women at village level produce sorghum juice for home consumption and sale. The short shelf life (2 to 3 days) of sorghum juice is a major problem for both the brewers and consumers of this drink. The aim of the study was to use 12 Combretum plants to improve the microbiological quality and shelf life of sorghum juice. Fresh stems and leaves of C. caffrum, C. vendae, C. erythrophyllum, C. elaegnoides, C. apiculatum, C. imberbe, C. adenogdium, C. padoides, C. bracteosum, C. kraussii, C. mkuzense and C. zeyherii were collected at Nelspruit, National Botanical Gardens, Mpumalanga, South Africa. Voucher specimens and tree labels were used to verify the identity of the plants. The stems and bark collected were cut into pieces and air dried for 30 days. When dried, the plant material was ground to a fine powder and stored in paper bags at room temperature. The wood was burnt in an open fire; fuel was not used to minimise contamination. The qualitative phytochemical composition of both the leaves and stems of Combretum plants analysed in this study revealed the presence of saponins, tannins, terpenoids, steroids, cardiac glycosides and flavonoids. The following phytoconstituents were lost in the ashes; tannins with the exception of C. mkuzense and C. padoides; cardiac glycosides and flavonoids. The quantitative phytochemical analyses revealed that both the leaves, stems and some ashes such as C. apiculatum and C. vendae contained appreciable levels of phenolic compounds, tannins and flavonoids. Quantitative analysis of antioxidant activity, the 2, 2, diphenyl-1-picrylhydrazyl (DPPH) assay was used as a screen test for the radical scavenging ability of the compounds present in the different 36 70% acetone extracts. DPPH screening method indicated great scavenging activity with the 70% acetone leaf extracts of C. kraussii, C. zeyherii and C. mkuzense. The leaf and stem extracts showed substantial great antioxidant activity in a concentration-dependent manner. There was a significant decrease in the antioxidant activity in the ashes (p=001), when compared to both the leaves and the stems. The proximate and nutritional analysis of the 70% acetone extracts were performed by AOAC and ICPE protocols, respectively. The results indicated that all the extracts had substantial amounts of ash, moisture, protein and energy. Mineral content of the plant parts was analysed as well, calcium had the highest concentration, while zinc was lowest in concentration. The mineral content decreased significantly in the stems (p ≤ 0.05) when compared to the leaves. There was a further decrease in mineral content with regard to the ashes with the exception of calcium. Based on these findings, the leaves and ashes of C. adenogonium and C. apiculatum could provide a good source of calcium in the diet, while C. adenogonium, C. bracteosum and C. apiculatum had high levels of sodium. A serial micro-dilution assay was used to determine the minimum inhibitory concentration (MIC) values for 70% plant extracts using tetrazolium violet reduction as an indicator of growth. Two Gram-positive (Stapylococcus aureus ATCC 29213 and Enterobacter faecalis ATCC 29212) and two Gram-negative (Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853) bacterial strains were used in this study. The leaves had good antibacterial properties with the lowest MIC value being 0.04 mg/ml against E. coli and S. aureus. E. faecalis was found to be resistant against all the leaves with the exception of C. imberbe. The stem extracts of Combretum spp. tested in the study showed antimicrobial properties with the lowest MIC value being 0.04 mg/ml against E. coli shown by C. bracteosum. However, E. faecalis was resistant against all the 12 plants tested. All the test microorganisms showed resistance to the ashes, with the exception of S. aureus, which was found to be susceptible to 75% of the test ash extracts with the lowest MIC value of 0.16 mg/ml. Cytotoxicity and anticancer activity of the acetone extracts of the 12 Combretum plants were evaluated using tetrazolium-based colorimetric assay (MTT assay) on A549 lung carcinoma cells. The assays revealed that 50% of the leaf extracts of tested plants showed cytotoxicity and cell proliferation inhibition in A549 lung carcinoma cells in a concentration-dependent manner. The A549 cells were more sensitive to the following plants: C. elaegnoides, C. erythrophyllum C. imberbe, C. kraussii and C. mkuzense. The following stems extract, C. adenogdium and C. caffrum did not have any anticancer activity, whereas C. apiculatum and C. bracteosum were only able to reduce cell viability to less than 60%. C. mkuzense, C. padoides, C. vendae and C. zeyherii acted in a concentration-depended manner with the greatest activity seen at the highest concentration (1000 µg/ml). The plants had activity at concentrations between 31.25 and 1000 µg/ml allowing only 20% and 50%, respectively, of the cells to remain viable. Ashes from C. mkuzense showed good anti-cancer activity at the highest concentration (1000 µg/ml) reducing cell viability to around 10%. Enterobacteriaceae, total coliform, S. aureus, B. cereus, E. coli and lactic acid bacteria viability were studied during the four weeks storage period of prepared sorghum juices. Juice samples were collected after preparation; the samples were serially diluted using peptone water. Tempo instrument (Biomereiux) was used to enumerate total coliform, total aerobic count, E. coli, S. aureus, lactic acid bacteria, enteric bacteria, yeast and mould using the most probable number following the manufacturers instruction. C. mkuzense and C. padoides plants were able to inhibit the growth of B. cereus, lactic acid bacteria and S. aureus during the first three weeks of storage. E. coli was not present throughout the four weeks storage time. Vitek 2 Compact (Biomereiux) was used for the characterisation and identification of the dominant bacterial isolates using biochemical reactions. The isolates were characterised by morphological differences. Sixty five percent of the isolates were the Enterobacter genus that are commonly found in soil, water, and sewage. The nutritional composition and sensory properties of the prepared sorghum juices treated with Combretum plants were investigated. All the juices had appreciable amounts of protein, ash and energy. Sorghum juice treated with ashes of C. caffrum, C. erythrophyllum and C. kraussii had the highest levels of proteins when compared with other treated sorghum juices. The sorghum juices prepared in the study had varying levels of trace element or minerals with potassium -(3, 55 – 104 mg/l) and calcium (3.2-148 mg/l). Similarly, cobalt (-1.22), coppr (-0.99), iron(-0.962), magnesium (0.004), sodium (-0.145), nickel (-2.7)) and zinc (-1.2)are present in very low amounts. The juices treated with ashes had relatively higher levels of calcium, potassium, magnesium and sodium. Sorghum juices treated with the ashes had better sensory and organoleptic properties when compared with those treated with the leaves. The juices treated with the ashes of C. caffrum and C. bracteseum were more accepted by most of the panellist when compared with other treated juices. Overall, this study presents valuable information on the phytochemical composition, nutritional composition and antioxidant properties of some Combretum species in South Africa. It recommended its use as food and in pharmaceutical preparations for the local industries. In addition, Combretum plants showing the effects tested in this study may be explored further for development into drugs. functional food as food preservatives and nutraceutical applications, beside their traditional use / University of Limpopo and Foodbev SETA

The use of Pulsed Energy (Flashbasttm) Technology (PET) to extend the shelf life of fresh fish fillets was studied. Unskinned fillets from fresh sea trout (Cynoscion regalis) and hybrid striped bass (Morone chrysops x ~ saxatilis) were treated with 7.45 Joules/cm² of PET, stored individually in sterile polyethylene bags, and kept in ice for 21 days at 3°C. Sensory data showed no significant differences (pâ ¤ 0.05) in the appearance, odor, texture, or taste of cooked samples from treated and control fillets, regardless of species. Raw sea trout fillets developed "alien" odors upon treatment which disappeared within the first week of storage and were not detected in cooked samples. These off-odors were significant (pâ ¤ 0.05) in the freshwater species only during the first three days post-treatment. Microbiological analyses revealed that PET reduced bacteria growing on the flesh surface and skin at significantly higher (pâ ¤ 0.05) rates than those in the flesh. Total coliforms were the most susceptible bacteria to PET. / Ph. D.

An enzyme-linked immunosorbent assay (ELISA) using polyclonal antibodies has been developed for the detection of the fluorescing group of Pseudomonas. The assay was used as a rapid test (6h) for predicting the shelf-life of pasteurized fluid milk. Milk samples were held at 7°C and tested weekly until determined to be unacceptable by daily sensory evaluation. Sterile milk samples were inoculated with target concentrations of 0 (control), 100, and 1000 cells/ml of Pseudomonas fluorescens on day 0. Samples were tested before and after preliminary incubations. Preliminary incubations conducted include milk alone and milk with broth (1:1) for 18h at 21°C. ELISA and plate counts were performed before and after preliminary incubation to determine the number of pseudomonads present and the relationship between ELISA and plate counts. These numbers were correlated to the shelf-life of each sample, as determined by sensory evaluation. Samples undergoing a preliminary incubation with only milk gave the best correlation to shelf-life (R=0.86). / Master of Science

Orientador: Benedito Carlos Benedetti / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Agrícola / Made available in DSpace on 2018-08-15T21:08:21Z (GMT). No. of bitstreams: 1 Bachelli_MaraLigiaBiazotto_M.pdf: 1116172 bytes, checksum: a831f41eca24b6d23a6b8523017e708e (MD5) Previous issue date: 2010 / Resumo: Este trabalho teve como objetivo avaliar os compostos dióxido de cloro, ácido peracético e ozônio, como agentes sanitizantes alternativos para alface minimamente processada em comparação ao hipoclorito de sódio. O mesmo foi conduzido em duas etapas, sendo adotada em ambas a mesma metodologia para o processamento mínimo, que consistiu em seleção, pré-enxágüe, corte, sanitização e enxágüe, centrifugação e embalagem. Na primeira etapa definiram-se as concentrações mais adequadas de dióxido de sódio, ácido peracético e água ozonizada, para serem utilizadas na segunda etapa. Nesta etapa, comparouse os três tratamentos com o sanitizante hipoclorito de sódio na concentração de 150 mg L-1 e imersão por 15 min., além do tratamento com água potável (controle). Na segunda etapa, dois ensaios foram realizados, um em julho/2009 e outro em outubro/2009, e em ambos a alface minimamente processada foi armazenado a 2+1ºC e as amostras foram submetidas a análises microbiológicas, físico-químicas e sensorial, no dia zero (antes e após sanitização) e aos 3, 6, 9 e 12 dias, além do monitoramento da composição gasosa no interior das embalagens. Na primeira etapa, os melhores resultados foram: solução de dióxido de cloro na concentração de 60 mg L-1 por 10 min. de imersão; solução de ácido peracético com 100 mg L-1 por 15 min. De imersão e água ozonizada na concentração de ozônio de 1,2 mg L-1 com tempo de imersão de 1 min. Na segunda etapa, todos os tratamentos de sanitização reduziram a contagem microbiana em comparação com a matéria-prima antes do processamento. A lavagem com água potável foi capaz de reduzir 1 ciclo logarítmico na contagem total de microrganismos aeróbios mesófilos e psicrotróficos, bolores e leveduras no primeiro ensaio, mas não foi suficiente para a redução de coliformes totais; porém, o mesmo não aconteceu no segundo ensaio. O dióxido de cloro foi o tratamento mais eficiente nos dois ensaios para a redução de coliformes totais passando de >1,1x10³ UFC g-1 (antes do processo) para <3,0 UFC g-1 (após sanitização). O ácido peracético foi o sanitizante que apresentou a maior redução para mesófilos e psicrotróficos no dia zero em relação ao produto antes do processamento, chegando a reduzir até 5 ciclos logarítmicos; porém, na avaliação sensorial no 6º dia o produto foi rejeitado, por apresentar manchas nas folhas e sua impressão global da aparência receber uma nota média muito baixa (3,76). O tratamento com hipoclorito de sódio recebeu a segunda maior média (7,86). O uso de água ozonizada não se mostrou eficiente na redução da carga microbiana, necessitando outros estudos em concentrações diferentes. De acordo com as análises microbiológicas a alface minimamente processada apresentou ausência de E.coli e de Salmonella spp. em todas as amostras. Tomando como base que níveis populacionais maiores que 105 UFC g-1 já são indicadores de final de vida de prateleira, pode-se concluir que, sob refrigeração a 2ºC, a durabilidade da alface minimamente processada foi de seis dias para os tratamentos utilizados / Abstract: This study aimed to evaluate the compounds chlorine dioxide, peracetic acid and ozone as alternative sanitizers for minimally processed lettuce as compared to sodium hypochlorite. The study was conducted in two stages, in both adopted the same methodology for the minimal processing, consisting of selection, pre-rinse, cut, sanitize and rinse, centrifugation and packaging. The first stage outlined the most appropriate concentrations of sodium dioxide, peracetic acid and ozonated water to be used in the second stage. In this step, it was compared the three treatments with sodium hypochlorite sanitizer at a concentration of 150 mg L-1 and immersion for 15 min. In addition to treatment with water (control). In the second stage, two experiments were conducted, one in July/2009 and another in October/2009, and in both the minimally processed lettuce was stored at 2 +1°C and the samples were subjected to microbiological, physicochemical and sensory analysis, in day zero (before and after sanitization) and at 3, 6, 9 and 12 days, in addition to monitoring the gas composition inside the package. In the first stage, the best results were: solution of chlorine dioxide at 60 mg L-1 for 10 min immersion; peracetic acid solution with 100 mg L-1 for 15 min immersion and ozonated water at 1.2 mg L-1 for 1 min immersion. In the second step, all sanitation treatments reduced the microbial count in comparison with the raw material before processing. Rinsing with water was able to reduce 1 log cycle in the total count of aerobic mesophilic and psychrotrophic bacteria, yeasts and molds in the first test, but was not sufficient to reduce total coliform, but it did not happen in the second test. Chlorine dioxide was the most effective treatment in two trials to reduce total coliform passing of> 1.1 x 10 ³ CFU g-1 (before trial) to <3.0 CFU g-1 (after sanitization). Peracetic acid was the sanitizer that showed the greatest reduction in bacteria mesophilic and psychrotrophic bacteria on day zero for the product before processing to reduce reaching 5 log cycles, but the sensory evaluation on the 6th day the product was rejected by presenting spots on the leaves, and overall bad aspect, which caused to receive a very low average score (3.76). Treatment with sodium hypochlorite received the second highest average (7.86). The use of ozonated water was not efficient in reducing microbial load, requiring further studies in different concentrations. According to the microbiological analysis, minimally processed lettuce showed absence of E.coli and Salmonella spp. in all samples. Based on that population levels greater than 105 UFC g-1 are already indicators of the end of shelf life, it can be concluded that, under refrigeration at 2°C, the durability of minimally processed lettuce was six days for all treatments / Mestrado / Tecnologia Pós-Colheita / Mestre em Engenharia Agrícola

Thesis (M.Sc. Agriculture (Horticulture)) -- University of Limpopo, 2022 / The most common postharvest limitation of litchi fruit is pericarp browning, which leads to consumer rejection of the solid fruit in the market even when the edible portion is not affected. Previously, sulphur dioxide (SO2) fumigation was used to control the browning and extend shelf life of litchi fruit. However, SO2 fumigation leaves undesirable residues, alters the fruit taste and may results in health hazards for consumers. An alternative method, namely, minimal processing was used to control pericarp browning and curb postharvest losses in litchi. Litchi fruit were harvested at two maturity stages (early harvest; 120 days after full bloom (DAFB), late harvest; 130 DAFB), peeled and immersed for two (2) minutes in three (3) solutions that represented treatments, namely 1) 1% citric acid 2) 1% calcium lactate and 3) a combination of citric acid and calcium lactate both at 1% measure. The untreated arils were dipped in sodium hypochloride (NaOCl) solution for 1 minute and represented the control samples. The treated arils were packed in sterilized clamshell containers and stored at 1±0.5°C and 95% relative humidity for 12 days, then held at 10±0.5°C for 2 days for shelf life study. As a result of the interaction effect of harvest stages and postharvest pre-treatments, least mass loss percentage (1.32%), juice leakage (1.8 ml per 120 g of fruit) and pH (4.18) was observed in litchi arils harvested late and treated with 1% citric acid only under cold storage. Under shelf life study, H2 control samples presented lower mass loss (2.8%) and juice leakage (4.2 ml per 120 g of fruit). At the end of cold storage, litchi arils harvested early and treated with 1% citric acid combined with 1% calcium lactate presented better tissue strength (56.0 N) and radical scavenging activity (36.6 mmol AAE/mL), while those harvested late presented higher ascorbic acid content (72.9 µg/mL), least microbial population and total colour change (3.5). However, at the end of shelf life storage, litchi arils harvested early and treated with 1% citric acid combined with 1% calcium lactate presented lower (3.1) total change in colour. Overall, harvesting the fruit late and treating with citric acid alone or combined with calcium lactate showed the potential of maintaining better aril quality with least microbial population for up to 12 days under 1±0.5°C storage, whereas harvesteing the fruit early and treating with citric acid alone or combined with calcium lactate showed the potential of maintaining better aril quality under shelf life storage. Keywords: Litchi chinesis sonn; calcium lactate; citric acid; maturity; fresh-cut. / Agricultural Research Council (ARC), National Research Foundation (NRF) and Agri-Seta

Thesis (M.Sc. (Horticulture)) -- University of Limpopo, 2022 / Cold storage is commonly used to prolong papaya fruit storability. Furthermore, the optimal recommended storage temperature is below 10℃ for export and distant market. However, chilling injury (CI) occurs at 10℃ or lower during prolonged cold storage. This condition hampered consumer acceptance, resulting in economic losses for producers and exporters. Therefore, the study aimed to investigate the potential of postharvest polyamine dips and storage conditions to improve the quality and shelf life of ‘Solo’ papaya fruit. The experiment was conducted as 4 x 2 factorial arranged in a completely randomised design (CRD) with eight replications. The fruits were treated with putrescine (PUT) (0 (control), 1, 2 and 3 mM) before storage for 21 days at 7.5 and 13℃ plus 5 days storage at ambient temperature. Additionally, the PUT effect on quality attributes and shelf-life were studied. The results showed that physiological and pathological disorders increased with progressive storage, irrespective of storage temperature. However, PUT treatment reduced the incidence of chilling injury and anthracnose at both 7.5 and 13℃. Additionally, the interaction of treatment and cold storage temperature significantly affected ‘Solo’ papaya fruit physical and biochemical quality attributes. Furthermore, treatment with 2 and 3 mM PUT concentration reduced changes in colour, mass, firmness, TA, and TSS compared to control. In conclusion, postharvest PUT improved ‘Solo’ papaya fruit quality and prolonged shelf-life. / AgriSETA (Agricultural Sector Training Authority)