D. Tech. Chemistry / The avocado oil contains compounds with potency against ailments caused by some bacteria, fungi, viruses as well as some insects and parasites. Present in the oil are long aliphatic hydrocarbons (acetogenins) documented to have a wide range of biological activities such as anticancer, antibacterial, antifungal, insecticidal and nematocidal properties and as a result the oil is fast gaining popularity amongst consumers. The demand and popularity of the oil makes it a target for contamination and adulteration of with cheaper oils. Chromatographic techniques such as Gas chromatography (GC) and High performance liquid chromatography (HPLC) are the frequently used methods of oil analysis to safe guard against adulteration. Derivatization of acetogenins uniquely found in avocado oil would provide derivatives which can be used as markers for authentication of the oil, an alternative method to fatty acid methyl ester analysis.

Background: Oil yield from avocado fruit may be influenced by fruit pre-treatment and extraction method. Unripe and ripe avocado fruit pieces were deep-frozen at −20 ◦C and either freeze-dried or oven-dried (80 ◦C). Oil yield from these samples was determined after extraction with hexane and supercritical carbon dioxide (SC-CO2). The fruit samples were examined using scanning electron microscopy before and after oil extraction. RESULTS: Average oil yield from ripe fruit (freeze-dried and oven-dried combined) was 72 g kg−1 higher than from unripe fruit for SC-CO2 extracts and 61 g kg−1 higher for hexane extracts. This may be due to enzymatic degradation of parenchyma cell walls during ripening, thus making the oil more available for extraction. Freezedried samples had a mean oil yield 55 g kg−1 greater than oven-dried samples for SC-CO2 extracts and 31 g kg−1 higher for hexane extracts. However, oil yields from ripe fruit (freeze-dried and oven-dried) subjected to hexane extraction were not significantly different. All hexane extracts combined had a mean oil yield 93 g kg−1 higher than SC-CO2 extracts. CONCLUSION: SC-CO2 may be more selective and may create paths of least resistance through the plant material. Hexane, on the other hand, is less selective and permeates the whole plant material, leading to more complete extraction and higher oil yields under the experimental conditions.

Zugl.: Braunschweig, Techn. Univ., Diss., 2007

Thesis (Ph.D.) -- University of Western Sydney, Hawkesbury, 1998. / Thesis submitted for the degree of doctor of philosophy. Includes bibliographical references (leaves153-167).

Thesis (MSc)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Historically the storage of South African plum fruit involved cold storage at single low temperatures (-O.5°C). The ever present problem of internal breakdown, however, led to the development of the dual temperature storage regime (a type of intermittent warming) which was found to restrict the level of internal breakdown. However, this temperature regime led to the development of or unmasking of gel breakdown (GB). During season one it was proposed that 'Songold' and 'Angeleno' plums could be stored at a single high temperature (7.5°C) during the shipping period (18 days) in combination with controlled atmospheres (CA). This was compared to the commercially used dual temperature regime (10 days at -O.5°C and eight days at 7.5°C). During season two the temperature regimes were adjusted to mirror the storage of the fruit from the date of harvest until the fruit is purchased. During the shipping period the dual temperature regime and the single high temperature regime were still compared. It was hypothesised that the fruit could be stored at the higher temperature in combination with CA during shipping, and this would allow the ripening of the fruit to be retarded, retaining good quality without exposure to the low, chilling inducing temperatures associated with the dual temperature regime. The storage of both plum cultivars at the single high temperature in combination with CA had a positive influence on delaying the ripening of the fruit. Most noticeable was the delay of fruit softening and the restriction of colour and GB development of the 'Songold' plums. Most importantly, these results were achieved without the fruit being exposed to the low, injurious temperatures associated with the dual temperature regime. It was, however, concluded that due to the suppressed climacteric trait of these plums more benefit could be gained from the higher temperature storage in combination with CA on climacteric plums which display stronger ripening patterns. In contrast to the plum industry, the use of CA in the storage of avocado fruit has risen to about 95% of the exported fruit. CA storage of avocados has shown positive results in retaining fruit firmness, restricting disorder development and extending the shelf life. Recently, research with l-methylcyclopropene (l-MCP) storage of avocados has been found to be as successful as CA storage and there is a belief that it will be the answer to storage for the avocado industry once registered for commercial use. During the first experiment, 'Fuerte' and 'Hass' avocados were treated with CO2 shocks (C02 levels which greatly exceed the initial intercellular concentrations of CO2 are known as CO2 shock treatments). These shock treatments were done over a series of three time periods and four CO2 concentrations for the 'Fuerte' avocados and two time periods and two concentrations for the 'Hass' avocados. Results were disappointing, as the fruit treated with CO2 were not able to retain their quality. For the second experiment, 'Fuerte' and 'Hass' avocados were treated with either CA or I-MCP, or CA and I-MCP in combination. Previous research had identified a positive synergistic effect when CA and I-MCP were combined, due to the fact that the treatments act at different points in the ethylene production process. Both the CA and I-MCP treatments, whether alone or in combination, had positive results in retaining firmness and extending the shelf life of the fruit. The treatments were also able to retain the quality of the 'Fuerte' avocados in terms of internal and, external physiological disorders. 'Hass' avocados, however, are known to be of excellent internal quality and none of the treatments had a greater percentage of sound fruit than the fruit which were stored in air. The extended ripening gained by treatment with I-MCP outweighed any increased loss due to fruit quality and in terms of the ease of application makes it superior to CA storage. However, before large-scale commercial application of I-MCP begins, much still needs to be learned about its use on avocados. Relative humidity (RH) control, forms an integral part of the storage of many fruit and vegetables. However, the difficulty in controlling and measuring RH has resulted in it being largely ignored. Research has shown that storage of fruit and vegetables at RH levels close to 95% has been able to restrict ripening and chilling injury development by decreasing the water stress on the fresh commodities during storage. During the final experiment, 'Fuerte' and 'Hass' avocados were placed at the commercial storage temperature and a chilling temperature. At each temperature, the fruit were either stored under a high or a low RH. Results were inconclusive, as the higher RH showed no signs of restricting chilling injury or any other disorders in the fruit. / AFRIKAANSE OPSOMMING: In die verlede is pruime in Suid Afrika opgeberg volgens 'n enkeltemperatuur-regime (-0.5°C). Interne verval (IV) van die pruime was 'n probleem en het gelei tot die ontwikkeling van die dubbeltemperatuur-opberging regime wat IV verhoed het. Dit het egter gelei tot die ontwikkeling of ontmaskering vanjelverval (IV). Vir seisoen een is voorgestel dat die opberging van 'Songold' en 'Angeleno' pruime gedurende die verskepingstyd (18 dae), teen 'n hoë enkeltemperatuur van 7.5°C gekombineerd met beheerde atmosfeer (BA) geskied. Dit is vergelyk met die kommersiële dubbeltemperatuur-opberging regime (10 dae by -0.5°C en agt dae by 7.5°C). Vir seisoen twee is die temperatuur regime aangepas om die opberging van die vrug vanaf die oesdatum totdat dit deur die verbruiker gekoop word, na te boots. Tydens die verskepingstyd is die dubbeltemperatuur-opberging regime steeds vergelyk met die enkeltemperatuur opberging. Die gestelde hipotese is dat die vrugte gedurende verskeping by hoë enkeltemperatuur gekombineerd met BA opgeberg kon word. Sodoende word rypwording vertraag en die kwaliteit van die vrug behou sonder dat die vrugte blootgestel word aan temperature wat koueskade sal veroorsaak. By beide kultivars het 'n hoë enkeltemperatuur, gekombineer met BA opberging, die rypwording van die vrugte vertraag. Mees opmerklik was die vertraging van die sagwording van altwee kultivars asook die vertraging van kleur ontwikkeling en JV van die 'Songold' pruime. Wat van belang is, is dat die resultate bereik is sonder dat die vrugte blootgestel was aan die lae temperature wat koueskade veroorsaak. Die onderdrukte klimakterium wat met 'Songold' en 'Angeleno' pruime verkry is toon dat pruim kultivars met sterker rypwordingspatrone meer sal baat deur opberging by hoë temperature saam met BA. In teenstelling met die pruim bedryf, word omtrent 95% van die avokado vrugte wat deur Suid Afrika uitgevoer word onder BA verskeep. BA opberging toon vir baie jare al dat dit 'n positiewe invloed op die vertraging van sagwording, die behoud van gehalte en die verlenging van die raklewe van avokados het. Onlangse navorsing het aangetoon dat I-metielsiklopropeen (I-MCP) 'n produk is wat BA opberging se plek kan inneem. Daar word geglo dit is die antwoord vir avokado opberging in Suid Afrika. Vir die eerste eksperiment het 'Fuerte' en 'Hass' avokados 'n CO2 skok behandeling ontvang (C02 vlakke wat die interne sellulêre konsentrasie van C02 oorskrei). Die skok behandelings was oor drie tydperke en vier konsentrasie vlakke gedoen vir die 'Fuerte' avokados en oor twee tydperke en twee konsentrasies vir die 'Hass' avokados. Die resultate was teleurstellend omdat die vrugte wat met die C02 behandel is nie hul gehalte kon behou nie. Gedurende die tweede eksperiment, was 'Fuerte' en 'Hass' avokados met BA of I-MCP, alleen of in kombinasie behandel. Navorsing het bewys dat daar 'n dubbelle effek is as BA en I-MCP saam gebruik word, omdat hulle etileen produksie deur verskillende maniere beheer word. Beide die BA en I-MCP behandelings, alleen of in kombinasie, het 'n positiewe effek uitgeoefen op die vrug deurdat dit fermheid behou en die raklewe verleng het. Die behandelinge het ook die kwaliteit van die 'Fuerte' avokados behou. 'Hass' is 'n avokado wat alreeds 'n baie goeie interne kwaliteit het. Vir dié rede het die vrugte wat net in lug opgeberg was die beste interne kwaliteit gehad. Maar die verlengde raklewe agv. die I-MCP behandeling is van groter belang as die kwaliteit wat verloor is. Dit, saam met die feit dat die toepassing van I-MCP behandeling baie makliker is as BA, maak dit die beter opsie. Voordat I-MCP kommersiël geregistreer is moet daar egter nog baie geleer word oor die produk sodat dit so effektief as moontlik gebruik kan word vir die opberging van avokados. Die beheer van relatiewe humiditeit (RH) word beskou as 'n groot veranderlike in die opberging van vrugte en groente. RH word egter meestal geïgnoreer in opberging omdat die beheer en meet daarvan moeilik is. Navorsing het al getoon dat indien die RH vlakke, gedurende opberging, nabyaan 95% gehou word, kan koueskade verlaag word deur die water dampdruk tekorte op die vars produkte te verlaag. Vir die finale eksperiment was 'Fuerte' en 'Hass' avokados opgeberg teen die kommersiële temperatuur sowel as 'n laer temperatuur. By beide temperature was die RH gewysig om laag of hoog te wees. Resultate was egter teleurstellend omdat die hoër RH nie koue skade of ander fisiologiese skade vertraag het nie.

The seasonality of avocado production leads to over-supplied markets during peak periods followed by shortages of fruit during other periods. The production of out of season avocado fruit was seen by Westfalia Estate as an opportunity to increase their profits. As the Estate is committed to supply Woolworths with fruit for 12 months of the year, this study was undertaken to investigate the production of out of season avocado fruit through chemical and physical manipulation of trees. Gibberellins (GA) are known to have many regulatory functions on various processes in plants, including flowering. Trials were conducted during 1999 in which the effect of gibberellic acid (G3) sprays on flowering of avocado was evaluated. A microscopic study revealed that the first signs of inflorescence development were already present in 'Hass' buds sampled in mid March. Secondary inflorescence axis meristems could be seen as small axillary meristems in the axils of the inner terminal bud bracts. GAJ sprays delayed the development of these secondary inflorescence axis meristems. In a more comprehensive study, the effect of single and multiple GAJ treatments (50 and 250 mg.L-1) on flowering of potted 'Fuerte', 'Hass' and 'Ryan' trees was evaluated. Depending on the timing of the application, single GA3 treatments did not affect (February), delayed (mid March and early April) or enhanced (late April and May) inflorescence development of avocado trees. However, none of these effects were significant. Multiple GA3 treatments applied over a four month period significantly inhibited inflorescence development. The effect on inflorescence development tended to increase with increasing number of sprays applied and with an increase in the concentration used. Timing of GA3 sprays proved to be crucial and determined what kind of effect was obtained. In order to inhibit flowering reliably, the first application must be applied before floral initiation and the last application during advanced stages of inflorescence development. In another trial, 'Fuerte' trees were de-flowered during the normal flowering period (August/September 1999) by the application of an Ethrel® spray. Three months after the de-flowering treatment, out of season flowering was induced by cincturing the trees. Out of season flowering and fruit set were observed in January/February 2000. Normal season fruit were harvested in April 2000 at a moisture content of 70%, whereas the out of season fruit were harvested in November 2000 at a moisture content of 62%. Although, the out of season yield (17.7 kg.tree-1) was significantly lower than the normal season yield (45.8 kg. tree-1), the extremely good prices obtained out of season makes this a highly profitable venture. Out of season fruit quality proved to be equal to or even better than the normal season fruit quality. The de-flowering treatment resulted in unnecessary stress being inflicted onto the trees and may be a limiting factor in the long term sustainability of out of season fruit production. In this regard, the use of G3 sprays to inhibit flowering during the normal season may eliminate the problems associated with the de-flowering treatment. / Dissertation (MSc (Agric) Horticultural Science)--University of Pretoria, 2005. / Plant Production and Soil Science / unrestricted

Please read the abstract in the section 00front of this document / Dissertation (M Inst Agrar ( Food Processing))--University of Pretoria, 2006. / Food Science / unrestricted

There is increasing interest in special heptose carbohydrates, their multifunctional roles from a plant physiological view point in fruit growth and development as well as in the whole plant in general due to their potential in mitigating photo-oxidative injury to the whole plant system and the image of avocado as ‘health fruit’. Studies have been carried out to investigate the role of avocado heptoses, rare carbohydrates predominantly produced in avocado. Several authors have documented various research findings and speculated on multifunctional roles of avocado special sugars. However, few reports have made an attempt to elucidate the multifunctional roles of avocado heptose carbohydrates as: ‘sources of energy’, storage and phloem-mobile transport sugars, and precursors for formation of antioxidants. Assessing the avocado carbohydrates over the plant growth and development during ontogeny may, therefore, offer clues to better understand whole plant behaviour. Plant sampling was carried out over different developmental stages. Using plants grown in the light versus etiolated seedlings; sugar determinations were also done to determine what sugar is produced from which storage organs. The sugars were extracted and analysed by isocratic HPLC/RID. The embryo had 47.11 % hexose and 52.96 % heptose sugars. The seed, however, also released significant amounts of D-mannoheptulose (7.09 ± 1.44 mg g-1 d. wt) and perseitol (5.36 ± 0.61 mg g-1 d. wt). Similarly fruit and leaf tissues had significant amounts of heptoses relative to hexoses at specific phenological stages. In postharvest ‘readyto-eat’ fruit the following carbohydrate concentrations were as follows:exocarp heptoses 13 ± 0.8; hexoses 4.37 ± 1.6 mg g-1 d. wt, mesocarp heptoses 8 ± 0.2; hexoses 3.55 ± 0.12 mg g-1 d. wt), seed heptoses (only perseitol) 13 ± 1.1; hexoses 5.79 ± 0.53 mg g-1 d. wt. The results of this experiment was the first to demonstrate that the heptoses D-mannoheptulose, and its polyol form, perseitol, are found in all tissues/organs at various phenological stages of avocado growth and development. Secondly, heptoses, as well as starch are carbohydrate reserves that are found in avocado. The heptoses, beyond being abundantly produced in the avocado plant, are also found in phloem and xylem saps as mobile sugars. The study also presents data on the interconversion of the C7 sugars Dmannoheptulose and perseitol. It is deduced that D-mannoheptulose can be reduced to perseitol, and perseitol can also be oxidized to D-mannoheptulose by enzymes present in a protein extract of the mesocarp. The potential catalyzing enzyme is proposed to be an aldolase, as electrophoretic determinations prove the presence of such an enzyme during various stages of development in various plant organs. Avocado heptoses play an important role in plant growth and development and in fruit in particular. Moreover, they are reported as sources of anti-oxidants, and contribute significantly to fruit physiology if they function in coordination with other anti-oxidants in fruit tissues. To evaluate the presence of anti-oxidant systems throughout avocado fruit development, various tissues were analysed for their total and specific anti-oxidant compositions. Total anti-oxidant levels were found to be higher in the exocarp and in seed tissue than in the mesocarp. While seed tissues contained predominantly ascorbic acid (AsA) and total phenolics (TP), the anti-oxidant composition of the mesocarp was characterised by the C7 sugar, D-mannoheptulose. Among the anti-oxidant enzymes assayed, peroxidase (POX) and catalase (CAT) were present in higher concentrations than superoxide dismutase (SOD) in mesocarp tissue. Different anti-oxidant systems seem to be dominant within the various fruit tissues. Carbohydrates are the universal source of carbon for cell metabolism and provide the precursors for the biosynthesis of secondary metabolites, for example via the shikimic acid pathway for phenols. The preharvest free and membrane-bound phenols, catechin and epicatechin, are distributed differently in the various fruit tissues. Membrane-bound and free phenols also play a role as anti-oxidants, with free ones being more important. KSil (potassium silicate) application to fruit as postharvest treatment was used to facilitate the release of conjugates to free phenols via lysis. This treatment improved fruit shelf life. Western blotting also revealed that postharvest Si treatment affects the expression of enzymatic anti-oxidant-catalase (CAT). Overall the thesis results revealed that C7 sugars have anti-oxidant properties and that D-mannoheptulose is the important anti-oxidant in the edible portion of the avocado fruit. Dmannoheptulose is furthermore of paramount importance as a transport sugar. Perseitol on the other hand acts as the storage product of D-mannoheptulose, which can be easily converted into D-mannoheptulose. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2009.

‘Fuerte’ makes up 25% of the avocados exported from South Africa to European markets and requires shipping periods of up to 28 days and a correctly managed cold chain. A temperature of 5.5°C and expensive CA and 1-MCP treatments are currently used to delay ripening over this lengthy cold chain; however, fruit still appear on the European market showing signs of softening and physiological disorders. Increased competition on the global market and the disadvantage of a particularly long distance to the European market has challenged the South African export industry. These challenges have necessitated improved road and sea transport logistics, co-ordination with producing countries which supply fruit to European markets over similar periods as South Africa, and research into ultra-low temperature storage to possibly enable future access to new lucrative markets in the USA, China and Japan. It is also known that there are various ‘weak links’ in this cold chain and that cold chain breaks are detrimental to fruit quality, but further research into the negative effects of these cold chain breaks at ultra-low temperatures was needed. Thus, the objective of the study was to determine the potential for shipping ‘Fuerte’ avocados at temperatures of 2°C as well as determining the effects of cold chain breaks on fruit quality, throughout the growing season and possibly for an extended period of 56 days. ‘Fuerte’ avocados were harvested at three different maturity stages reflecting early-, mid- and late-season fruit, with moisture contents of 74%, 68% and 63%, respectively. Fruit were stored at 2°C or 5.5°C, treated with 1-MCP and waxed. Additionally cold chain breaks (24 hour delay and break at 14 days) were implemented. Fruit softening, mass loss, days-to-ripening, external and internal quality as well as antioxidant levels and total sugar levels were determined. The first aim was to determine whether a lower than currently used storage temperature could be a successful alternative to 1-MCP use. A storage temperature of 2°C provided good internal quality as well as reduced mass loss and fruit softening, which is related to the slightly reduced use of C7 sugars at 2°C compared with 5.5°C. Although the overall occurrence of external chilling injury was relatively low, 2°C storage caused a notably higher occurrence of external chilling injury than 5.5°C storage, particularly early in the season, but extended the days-to-ripening. Unfortunately, no correlation between the anti-oxidants in the exocarp and external damage was found. Waxing significantly reduced the external damage on fruit stored at 2°C, so much so, that the treatment combinations of ‘2°C, no 1-MCP, waxed’ showed no external chilling injury throughout the season. Further, waxing fruit at 2°C could eliminate the need for 1-MCP, delivering a product of the required shelf-life and quality. Best results were achieved for mid-season fruit stored at 2°C. Late-season fruit would potentially be the most profitable to store at this low temperature, however, body rots (anthracnose and stem-end rot) were more common in the late-season. Storage at 2°C can therefore maintain the internal quality over a storage period of 28 days and be a potential alternative to 1-MCP use as the season progresses. The effect of cold chain breaks on fruit quality was then investigated and showed that both a delay and a break in the cold chain increased mass loss and fruit softening, reduced days-to-ripening and increased external chilling injury, especially early in the season. Water loss was the main contributor to the decreased fruit quality which resulted from the delay in cooling, increasing external damage significantly, particularly early in the season. The break at 14 days had a marked effect on physiological activity of fruit during storage, seen mainly in the increased metabolic activity, resulting in increased fruit softening and water loss during storage and a decrease in C7 sugars and thus shelf-life, particularly for fruit stored at 5.5°C. Importantly, 1-MCP use and storage at 2°C reduced the effects of cold chain breaks with respect to fruit softening, however, lowering the storage temperature had a greater negating effect than 1-MCP and could be a successful alternative to the use of 1-MCP. The internal quality throughout the experiment was very good, with few internal disorders and no significant treatment effects on internal quality and C7 sugar concentrations. Overall, a break in the cold chain, before and during cold storage, resulted in a marked reduction in fruit quality. The storage temperature of 5.5°C should not be used for a 56 day storage period as it resulted in significant fruit softening during storage, even when 1-MCP was used, and resulted in significantly more external chilling injury in the mid- and late-season than at 2°C. Storage of 1-MCP treated, waxed fruit at 2°C, resulted in the best shelf-life and fruit quality, particularly mid-season fruit which had negligible external chilling injury and 100% sound fruit. Early-season fruit suffered significant external chilling injury at 2°C and late-season fruit had the highest body-rots and internal disorders at this storage temperature. Although mid-season fruit could be successfully stored at 2°C for 56 days, the use of a 56 day storage period is not recommended as a practical storage period, due to the high risk of external damage, particularly if maturity levels are not optimum and trees and fruit are not of the highest quality. Overall this thesis has shown that 1-MCP treatment can play an important role early in the season when fruit are susceptible to external damage, however, storage at 2°C results in good quality fruit and, when used in conjunction with waxing, appears to be a viable alternative to the use of 1-MCP, particularly later in the season. Further, the negative effects of cold chain breaks on fruit quality have been demonstrated and, importantly, the storage temperature of 2°C negates the fruit softening effects of these breaks, even if 1-MCP is not used. / Thesis (M.Sc.Agric.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Thesis (MSc. Agriculture (Horticulture)) -- University of Limpopo, 2016 / The Agricultural Research Council-Institute for Tropical and Subtropical Crops (ARC-ITSC) is continuously developing new avocado selections, in order for the South African Avocado Industry (SAAI) to remain competitive in various international avocado markets. However, information on the response of some of these selections, including ‘Fuerte 2 and 4’, ‘BL1058’ and ‘H287’ to low temperature storage and ripening physiology, has not been investigated. Thus, the objective of this study was to evaluate the effect of harvest season and ripening duration on the physico-chemical properties of newly developed ‘Fuerte-type’ avocado fruit selections during ripening. ‘Fuerte-type’ avocado fruit were indexed for maturity using moisture content, thereafter harvested and stored at 5.5°C for 28 days during the 2014 and 2015 harvest seasons. The experiment comprised five treatments: control (commercial ‘Fuerte’), ‘Fuerte 2 and 4’, ‘BL1058’ and ‘H287’ arranged as a factorial in a completely randomised design (RCD) with 3 replicates. The treatment factors were: (i) 2 x harvest seasons, (ii) 5 x selections and (iii) 6 x ripening days. After withdrawal from low storage temperature, fruit were ripened at ambient temperature. During ripening, the following physico-chemical properties were evaluated; external chilling injury, electrolyte leakage, mass loss, firmness, respiration rate and peel colour. Results showed that selections and harvest seasons had no significant effect (P=0.668) on the moisture content of the evaluated ‘Fuerte-type’ avocado fruit. After withdrawal from low storage temperature, there was a significant interaction (P˂0.05) between selections and harvest seasons on external chilling injury and electrolyte leakage. Results further showed that external chilling injury correlated with electrolyte leakage during both harvest seasons. Treatment factors had no significant effect (P=0.997) on mass loss. Similarly, treatment factors had no significant effect (P=0.139) on firmness. However, selection ‘H287’ had hard skin with an average firmness of 83.44 densimeter units during ripening in both harvest seasons. Treatment factors were highly significant (P˂0.05) on respiration rate. Respiration rate followed a climacteric pattern and the magnitude of climacteric peak and day of occurrence varied amongst selections during both harvest seasons. Ripening percentage differed significantly (P˂0.05) amongst harvest seasons, selections and ripening days. Treatment factors had no significant effect on lightness (P=0.711), chroma (P=0.378) and hue angle (P=0.536) skin colour parameters,however, variations were recorded as a result of the cold damage black spots. The results indicated that the ‘Fuerte-type’ avocado selections had poor storage qualities. Further studies are required to evaluate physico-chemical properties during low storage temperature and the effect of season, production conditions and maturity level on development of chilling injury. In addition, studies on application of treatments to reduce chilling injury symptoms and analysis of bioactive compounds should be considered for conclusive recommendations. Thereafter, the selections can be planted in different production regions to assess and select the best producing and quality combinations for a given region as part of phase III of the project / Agricultural Sector Education Training Authority (AgriSeta) and National Research Foundation (NRF)