Thesis (MScFoodSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Postharvest fruit loss is a major challenge in addressing food security, sustainable management of resources and profitability of agribusiness. The incidence of postharvest loss and changes in physico-chemical properties of three types of fruit (peaches, pears and oranges) were evaluated at retail and during post-purchase storage. The amount of physical loss at the three retail outlets studied ranged from 3.61% to 18.09% among the fruit types, with the highest incidence occurring in peaches. The estimated annual national physical loss at retail was 418 tons for pears, 1000 tons for oranges, and 7 240 tons for peaches. Based on the WHO recommended 146 kg per capita per year consumption of fruit, the total loss of the three types of fruit was sufficient to meet the dietary fruit requirements of 50 000 people per annum. Similarly, based on the recommended daily allowance of 50 mg of ascorbic acid, these losses could meet the annual vitamin C needs of 82 000 people. The estimated monetary value of the losses at retail ranged from R2.2 million to R96.87 million per annum depending on fruit type and retail outlet. The land wasted to produce lost fruits was 1965 ha while energy wasted was 32.77 x 106 MJ. Greenhouse gas emission of the losses was 2870 tons CO2eq and total water footprint 68 0000 m3. Losses were mainly due to the presence of severe physical damage, rots and physiological disorders. There were significant variations in physico-chemical properties of fruit of the same type from different retail outlet. Although ambient temperature storage improved fruit colour and some chemical constituents responsible for palatability, it was associated with high physical and nutritional (vitamin C) losses. Results from this study show that appropriate harvesting maturity, packaging and maximum care in fruit handling is essential in reducing postharvest losses. Efficient cold chain management and fruit inspection for rots and damages could help to reduce subsequent spoilage at retail and during post-purchase storage. Given that the incidence of postharvest fruit loss observed at retail is the result of cumulative effects along the supply chain, further studies are warranted to map fruit history and magnitude of losses along the value chain. / AFRIKAANSE OPSOMMING: Naoesvrugteverlies is ‟n groot uitdaging in die strewe na voedselsekerheid, volhoubare hulpbronbestuur en winsgewende landbousake. Die voorkoms van naoesverlies sowel as fisiko-chemiese naoesveranderinge by drie vrugtesoorte (perskes, pere en lemoene) is gevolglik by kleinhandelsafsetpunte én gedurende berging ná aankoop beoordeel. Die graad van fisiese verlies by die drie betrokke kleinhandelspunte het gewissel van 3,61% tot 18,09% tussen die vrugtesoorte, met die hoogste verlies by perskes. Die geraamde jaarlikse nasionale fisiese verlies by die kleinhandelspunte was 418 ton pere, 1 000 ton lemoene en 7 240 ton perskes. Op grond van die Wêreldgesondheidsorganisasie se aanbevole jaarlikse vrugte-inname van 146 kg per persoon, was die totale verlies van die drie vrugtesoorte genoeg om aan die vrugtedieetvereistes van 50 000 mense per jaar te voldoen. Op grond van die aanbevole daaglikse inname van 50 mg askorbiensuur, kan hierdie verlies eweneens in die jaarlikse vitamien C-behoeftes van 82 000 mense voorsien. Die geraamde geldwaarde van die verlies by die kleinhandelspunte strek van R2,2 miljoen tot R96,87 miljoen per jaar, na gelang van die vrugtesoort en bepaalde kleinhandelspunt. Die vermorste grond om die verlore vrugte te produseer, was 1 965 ha, terwyl energievermorsing op 32,77 x 106 MJ te staan gekom het. Kweekhuisgasvrystellings met betrekking tot die verlies was 2 870 ton CO2e, en die totale watervoetspoor 68 0000 m3. Vrugteverlies kon hoofsaaklik aan ernstige fisiese skade, verrotting en fisiologiese afwykings toegeskryf word. Daar was beduidende variasies in die fisiko-chemiese eienskappe van dieselfde vrugtesoort by verskillende kleinhandelaars. Hoewel berging by omgewingstemperatuur vrugtekleur en bepaalde chemiese komponente vir smaaklikheid verbeter, word dit ook met groot fisiese en voedingstof- (vitamien C-) verliese verbind. Die resultate van hierdie studie toon dat toepaslike oesrypheid, die regte verpakking en maksimum sorg in vrugtehantering noodsaaklik is om naoesverlies te verminder. Doeltreffende koelkettingbestuur en vrugte-inspeksie vir verrotting en skade kan latere bederf by kleinhandelsafsetpunte sowel as gedurende berging ná aankoop help beperk. Aangesien die naoesvrugteverlies wat by die kleinhandelspunte waargeneem is uit kumulatiewe faktore in die verskaffingsketting spruit, is verdere studies nodig om vrugtegeskiedenis na te spoor en die omvang van die verlies in die algehele waardeketting te bepaal.

Please read the abstract in the section 00front of this document / Dissertation (MSc (Agric) Food Sience and Technology)--University of Pretoria, 2005. / Food Science / unrestricted

The South African fresh fruit industry is a significant exporter, accounting for approximately 45% of the country’s agricultural exports. Of the total exported fruit in the 2005/06 season, 60% was subtropical fruit. However, certain physiological rind disorders such as mango lenticel damage and citrus rind pitting are frequently observed, reducing the commercial value of the fruit. This thesis deals with the epidemiology of these rind physiological disorders, in an attempt to obtain basic information that could serve as a guideline to predict and manage the fruit susceptibility to these disorders. The study further investigated the relative effects that certain pre-harvest factors have on the postharvest development of these disorders. Factors of particular interest were harvest maturity, climate and the mineral content of the fruit. Rind pitting is a physiological disorder of citrus that develops during storage. A study was conducted to investigate the relative effects that certain pre-harvest factors have on the post-harvest development of superficial rind pitting in ‘Benny Valencia’ oranges. Factors of particular interest were harvest maturity, climate and the mineral content of the fruit. In addition, trees were treated with two different formulations of nitrogen viz. limestone ammonium nitrate (LAN) and a slow release nitrogen fertilizer (Horticote®), during March 2006. The fruit were then sampled on a two-weekly basis over a period of three months. On each sampling date a set of quality related readings, such as juice sugar and titratable acid concentration were taken, after which the mineral concentration of the exocarp and mesocarp was measured. Fruit were also stored under export simulation conditions. The results indicate that fruit from trees that received additional N were more susceptible to rind pitting than those from control trees. Of the two N applications, fruit from trees that received slow release N were more susceptible to rind pitting than fruit from trees that received the LAN treatment. Another important observation made was that the nitrogen concentration of oranges from trees that received extra nitrogen fertilizer was lower than that from the controls. In addition, experimental fruit were smaller than control fruit. Fruit from trees that received the slow release nitrogen treatment were smallest. A sink/source hypothesis aimed at explaining this phenomenon has been formulated and is currently being investigated. A number of control mechanisms are also being explored. Mango lenticel damage is a serious defect that occurs on the rind of the fruit. This condition causes fruit to attain a speckled appearance and become unattractive to the buyer. Each season, the disorder reduces the packout of fresh fruit by about 16%. Several preharvest factors play a critical role in the postharvest development of lenticel damage. Preliminary studies have shown that the incidence of lenticel damage has some relationship to fruit moisture and fruit nutrient concentration, depending on which of these factors first achieve a critical threshold. A study was conducted to develop appropriate skin moisture content parameters to predict lenticel damage potential before harvest. The study further aimed to provide certain biological markers regarding appropriate nitrogen fertilization practices to reduce lenticel damage. To do this, two trials were conducted approximately a month before harvest. Firstly, a plastic ground cover to restrict water supply was laid under ‘Tommy Atkins’ trees at Numbi Estates in the Hazyview area of the Mpumalanga province, South Africa. Secondly, additional nitrogen was applied as three different formulations, viz. limestone ammonium nitrate (LAN), potassium nitrate (KNO3), and a slow release nitrogen fertilizer under trade name Horticote®, to two ‘Tommy Atkins’ and two ‘Keitt’ orchards at Bavaria Estates in the Hoedspruit area of the Limpopo province, South Africa. Fruit samples were harvested, packed and stored at different intervals after rain during January 2006. With regard to lenticel damage on ’Tommy Atkins’ fruit from Numbi, there was no significant difference between the control and plastic cover treatments. However, when compared to fruit from other localities, the Numbi fruit had the highest incidence of lenticel damage, followed by the conventional orchard at Bavaria. The Numbi fruit, which had the highest incidence of lenticel damage, also had the highest pulp and skin nitrogen concentration. Of the four treatments at Bavaria, the LAN treatment had the highest incidence of lenticel damage, but the pulp and skin nitrogen concentrations of this treatment were comparable with the other treatments. The organic fruit had significantly lower lenticel damage incidence and also had the lowest pulp and rind nitrogen concentrations. Similarly, ‘Keitt’ results showed that the intensity of lenticel damage was significantly higher in the orchard that received additional nitrogen in the form of LAN. From the results it was, however, not possible to formulate nitrogen-lenticel damage correlations. The study failed to prove the case for a direct relationship between the disorder and with nitrogen, as there were no significant or consistent correlations with nitrogen content. An interesting relationship was nevertheless observed between lenticel damage and the time of harvest before and after rainfall. The results indicated that both ‘Tommy Atkins’ and ‘Keitt’ fruit become more susceptible to lenticel damage when harvested a day after rainfall and this gradually reduces afterwards. The effect of rainfall in this regard and a sink-source hypothesis arising from these observations are also discussed. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.