Improvement of fruit product quality and shelf life by changing temperature conditions during transport and storage

PhD ThesisThe present study aimed to investigate whether the temperatures usually applied in the supply chain during transport and storage may be too low for optimal sensory and nutritional quality at the time of purchase and after various post-sale periods in a range of fruit. This research began by investigating the effect of temperature on the quality of ten shop bought fruit (peaches, plums, nectarines, strawberries, red grapes, green grapes, mandarins, plum tomatoes, cherry tomatoes and round salad tomatoes) by keeping them at either refrigerator (6°C) or room (22°C) temperature, such as a consumer would after purchase. These fruit were chosen as they were either ASDA’s top 10 sold species in 2011, or they had been reported problematic in terms of shelf life (peaches, plums and nectarines). This experiment showed that refrigerator temperatures improved fruit firmness and reduced weight loss, but had a negative effect on the taste of round salad tomatoes, grapes and nectarines, most likely as a symptom of otherwise asymptomatic chilling injury (CI). The research that followed investigated the effects of keeping round salad tomatoes at a room temperature (RT) of 23°C, ASDA’s actual supply chain (SC) temperatures (average 12˚C) or an intermediate temperature of 15˚C (IT) for 7 days. Fruits from each treatment were then either kept at post-sale treatment RT (SCRT/RTRT/ITRT) or kept cold at 5°C (F) (SCF/RTF/ITF), until the end of their shelf life (any visible signs of pathogen infection or more than 15% skin wrinkling). Results showed clear differences in consumer preference after 7 days storage, with consumer scores for SC tomatoes always being significantly lower than those for RT tomatoes in all sensory categories (colour, ripeness, moistness, aroma, sweetness, acidity, flavour, overall opinion), except acidity, firmness and crunchiness. IT treatment delayed the onset of ripening with respect to colour, firmness (instrumental and sensorial) and weight loss compared with RT treatment, and IT treatment improved consumer preferences scores compared with the results of SC tomatoes; however, this was not on par with those from RT treatment. RT treatment also produced the highest lycopene accumulation compared with SC or IT tomatoes during the pre-sale storage phase and refrigeration temperatures during post-sale storage, although IT pre-sale treatment did improve lycopene accumulation compared to SC pre-sale treatment. iv After 11 or 15 days in storage, tomatoes from the coldest treatment (SCF) were consistently scored significantly lower in sensory preference than those that had any form of RT storage, showing the detrimental effects of too low temperatures on tomato sensory outcome. Post-sale F treatment also always reduced tomato disease resistance compared with post-sale RT treatment, and those from the coldest treatment SCF always had the lowest shelf life throughout this study, while tomatoes from SCRT or RTRT treatment had the longest shelf life in terms of resistance to disease infection. The results from this study can be used to update recommendations concerning optimal handling temperatures and highlights the importance of keeping tomatoes out of the refrigerator after purchase. This research demonstrates the need for further exploration into the optimisation of the temperatures used for post-harvest storage of fruit, and suggests that the optimal temperatures for the storage and transport of tomatoes during the supply chain are somewhere between 15°C and 23°C, or above.unrestricted educational donation from ASDA and by the University of Newcastle Agricultural Society (UNAS