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Tesi etd-03222012-144617

Thesis type
Tesi di dottorato di ricerca
Pre- and post-harvest factors influencing quality, organoleptics, nutrition properties and physiology of fresh-cut fruits
Settore scientifico disciplinare
Corso di studi
tutor Prof.ssa Guidi, Lucia
commissario Dott. Pardossi, Alberto
commissario Dott. De Pinto, Maria Concetta
commissario Dott. Lenzi, Anna
commissario Dott. Tomás Barberán, Francisco A.
tutor Prof. Massai, Rossano
Parole chiave
  • softening
  • fresh-cut
  • Malus domestica
  • bioavailability
  • cold storage
  • bioactive compounds
  • Actinidia deliciosa var. Hayward
Data inizio appello
Riassunto analitico
Food is anylonger considered just a source of nutrients indeed the protective and functional meaning it has assumed during times is strictly linked to the concepts of maintenance and implementation of human well-being. Oxygen hides in itself the concept of life underlying the fact that most of the organisms cannot live in absence of oxygen. However, its use is also associated with the generation of reactive oxygen species (ROS) that are the radicals generated by the organism known to be responsible for the oxidative damage of biological macromolecules such as DNA, carbohydrates and proteins. Biological damages prevention and detoxification processes are enzymatically or non-enzymatically antioxidant systems that can be activated by the organism determining a significative delay or inhibition of ROSs. These antioxidants substances are highly concentrated in plant tissues and represent the preferential target for oxidants and free radicals thus exerting a cells protective role against oxidative stress, for both humans and animals. Moreover, they are very important in food preservation, slowing down processes like deterioration or colour loss due to oxidation processes. The most preeminent representative compounds exherting an antioxidant activity in human diet are ascorbate (vitamin C), tocopherols (vitamin E), carotenoids and flavonoids.
Ready-to-eat foods like fruit and vegetables, are quick products, time saving, fresh, highly nutritious and low priced, all reasons why they are considered products with several added values, full of benefits. However, in respect to entire fruits or vegetables, fresh-cut products have a shorter shelf-life due to the higher metabolic activity which is stimulated by a tissues’ wounding. In fact, even if these kinds of products undergo a minimal processing, operations like peeling, cutting, slicing, are the causes of mechanical tissue injuries that are responsible for a reduced life. Moreover, the recent awareness of the existence of a large group of organic bioactive compounds, that are not strictly required in the diet but that can promote good health and prevent diseases, led consumers to look for good quality parameters such as texture, flavor and health-promoting compounds, that are all considered important internal quality attributes. Fruit quality, as well as vegetable one, can be improved by accurate selection on genotype, agricultural practices, such as water management, fertilization, and environmental conditions, in terms of light exposition, temperature and air composition. Because of the fact that there are several factors belonging to both the periods before and after harvest that are involved in fruit development and in fruit quality determination, the general aim of the studies conducted was the evaluation of the influence of pre- and post-harvest factors over quality, organoleptics, nutrition properties and physiology of fresh-cut products made from apples and kiwifruits.
Regarding apple fruit, a study evaluating the effects of the cold-storage on nutritional and organoleptics quality of slices prepared from Red Delicious and Granny Smith apples was carried out. In addition to, evaluations on the influence of ClO2 and/or ascorbic acid treatments as preserving strategies for fresh-cut products quality improvement were also examined. The study led to the conclusion that qualitative intrinsic characters of whole fruits as well as sanitizing and antioxidant treatments used for fresh-cut apple fruits had a statistically significant influence on product shelf life and aspect, in terms of flesh firmness, flavor, tissue browning and phytochemical content.
From a different perspective, the effect of 1-MCP treatment and two different holding times for short-term post-controlled air storage (PCAAS) treatment were considered to evaluate quality retaining capacity and physiology of fresh-cut slices made from apples belonging to AmbrosiaTM cultivar. The most dramatic effect of the PCAAS treatments was to reduce the accumulations of soluble phenolics, which is likely the reason that o-quinone accumulations were also inhibited in treated fruit. The consequent reduction in browning potential may be the explanation as to why PCAAS treatment has been shown to reduce fresh apple slice browning in previous work. In this study polyphenol oxidase (PPO) activity was not detected in slices treated with calcium ascorbate (CaAsc).
In addition, bioaccessibility in the small intestine of dietary polyphenols was estimated considering four different apple varieties. The study was conducted in order to quantify the total oxyradical scavenging of the original samples compared to the potentially bioavailable residues of the enzymatic in vitro digestion process. This part of the study also focused on the determination of dietary fiber content in the attempt to understand the amount of polyphenols associated to the indigestible fraction. Significant differences in reducing capacity (total phenolics content) of the four cultivars were observed when intact apples were measured, however, digestion of the apples resulted in significantly reduced reducing capacity in the dialyzable soluble fraction of all cultivars. Differences between the cultivars were not great for reducing capacity after digestion, suggesting that breeding for higher phenolics may not lead to significantly healthier outcomes for consumers. Similar results were seen in the peroxyl radical (TOSC) capacity analyses, which were again highly correlated to phenolic contents. Further analysis determined that one of the mechanisms for loss of soluble phenolics could be attributed to binding with insoluble fiber during digestion.
In regards to kiwifruit, the evaluation of organoleptics and nutritional characteristics at different times of cold storage was performed. Moreover, kiwifruit quality parameters were analyzed after minimal processing in order to understand the effect of the storage conditions and of the light or shade incidence – dependent on fruit canopy position - on the shelf life of fresh-cut kiwifruit. Even when stored for the longest period (150 d) kiwifruit preserved good quality parameters. In the attempt to evaluate together the influences of storage time, light influence and minimal processing we observed that when processed as fresh-cut over both storage periods, 75 and 150 d, kiwifruits were characterized by a decrease in organoleptic parameters that was evident also for nutritional aspects only after 24 hours from minimal processing. The best quality and nutritional retention was found for fruits grown in light condition after 75 d of cold storage. Differently, when vitamin C content was considered it was possible to reach the conclusion that the longest the storage period the worse the influence on this molecule retention, much more than the impact of light/shade conditions. Sunlight fruit exposure resulted to have a great influence particularly on enzymatic activities directly involved in softening processes. In conclusion, data suggests that the quality of kiwifruits and their capability to be stored as fresh-cut products is influenced by pre-harvest factors. The answer is complicated by the fact that organoleptics and nutritional indices did not respond in the same manner to these factors.