Browsing by Author "Meyer, Marjolaine D."

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    Biochemical and textural ripeness assessment of avocado fruit from different origins
    (Ishs; 1999, 2010-10-06T00:00:00Z) Landahl, Sandra; Meyer, Marjolaine D.; Terry, Leon A; Herppich, W. B.
    Stage of ripeness and quality of avocado is notoriously difficult to assess by conventional methods. Texture is a very important determinant of avocado fruit quality and can change radically during storage. The difficulties in determining avocado quality are related, in part, to the spatial heterogeneity of fruit characteristics during ripening. The aim of this study was to assess the discriminatory capabilities of physiochemical properties to determine ripeness of imported 'Hass' avocado fruit. Fruit were stored at 12°C and sampled at regular intervals. Using a previously unreported method, the texture of different slices from individual fruit was measured during ripening. Maximum load, elasticity and viscosity of fruit tissue were measured using a universal testing machine fitted with a 500N or 5N load cell. The same tissue slice was then further processed prior to subsequent quantification of non-structural carbohydrates (NSCs) and fatty acid methyl esters using standard high performance liquid chromatography coupled to evaporative light scattering detection and gas chromatography coupled to flame ionisation detection, respectively. Spatio-temporal differences in maximum load, elasticity, viscosity, NSCs and fatty acid composition were found in avocados from different origins. Results of measured texture and target analytes were used to differentiate avocado fruit into definable groups using partial least squares discriminant analysis.
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    Effect of controlling ethylene on ripening of avocado cv. hass fruit
    (Cranfield University, 2010-05) Meyer, Marjolaine D.; Terry, Leon A.
    Rigorous control of ethylene inside storage atmosphere is cardinal to maintain quality of climacteric fruit, including avocado cv. Hass. This can be achieved using the ethylene action inhibitor, 1-methylcyclopropene (1-MCP). The recent development of a novel palladium (Pd)-based ethylene scavenger, e+® Ethylene Remover, provides a new opportunity to delay avocado fruit ripening. A new method was developed to sequentially extract and quantify both lipids and sugars from the same avocado mesocarp tissue sample. Extraction by homogenization with hexane yielded slightly less oil than the standard Soxhlet technique whilst the fatty acid profiles of the oil extracts were similar. Extraction of the resulting filter residue with methanol (62.5%, v/v) better recovered sucrose, perseitol and mannoheptulose as compared to ethanol (80%, v/v). The new method has a shorter extraction time, lower extraction temperature and requires less solvent. Presence of e+® Ethylene Remover in storage atmosphere removed all ethylene and accordingly delayed the ripening of avocado cv. Hass stored at low temperature. 1-MCP also inhibited ripening, yet, unlike e+® Ethylene Remover it impaired subsequent ripening. It was possible to slow down the ripening rate after the climacteric has been induced by removing ethylene below 1 μL L-1 in presence of e+® Ethylene Remover, and the scavenger was effective in combination with modified atmosphere packaging (MAP). Blocking ethylene action or removing ethylene did very slightly affect the fatty acid composition of the mesocarp oil. Depending on the origin and maturity of the fruit, 1-MCP and e+® Ethylene Remover better maintained seven-carbon sugars concentrations in mesocarp. Results support the view that mannoheptulose and perseitol could be important features of the avocado ripening process but more research is necessary to elucidate their exact function. Mesocarp abscisic acid (ABA) was quantified using a newly developed LC-ESIMS/ MS method. ABA increased as fruit ripened but appeared to be at least partly regulated by ethylene. Whether ABA influences the ethylene-associated ripening in avocado cv. Hass remains to be determined in future.
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    Investigation into the role of endogenous abscisic acid during ripening of imported avocado cv. Hass
    (Wiley, 2017-02-23) Meyer, Marjolaine D.; Chope, Gemma A.; Terry, Leon A
    BACKGROUND The importance of ethylene in avocado ripening has been extensively studied. In contrast, little is known about the possible role of abscisic acid (ABA). The present work studied the effect of 1-methylcyclopropene (1-MCP) (0.3 μL L−1), e+® Ethylene Remover and the combination thereof on the quality of imported avocado cv. Hass fruit stored for 7 days at 12 °C. Ethylene production, respiration, firmness, colour, heptose (C7) sugars and ABA concentrations in mesocarp tissue were measured throughout storage. RESULTS Treatment with e+® Ethylene Remover reduced ethylene production, respiration rate and physiological ripening compared with controls. Fruit treated with 1-MCP + e+® Ethylene Remover and, to a lesser extent 1-MCP alone, had the lowest ethylene production and respiration rate and hence the best quality. Major sugars measured in mesocarp tissue were mannoheptulose and perseitol, and their content was not correlated with ripening parameters. Mesocarp ABA concentration, as determined by mass spectrometry, increased as fruit ripened and was negatively correlated with fruit firmness. CONCLUSIONS Results suggest a relationship between ABA and ethylene metabolism since blocking ethylene, and to a larger extent blocking and removing ethylene, resulted in lower ABA concentrations. Whether ABA influences avocado fruit ripening needs to be determined in future research. © 2017 Society of Chemical Industry
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    Spatio-temporal postharvest changes in texture and fatty acid profiles in avocado fruit from different origins
    (2008-06-29T00:00:00Z) Landahl, Sandra; Terry, Leon A; Meyer, Marjolaine D.
    The degree of ripeness of many climacteric fruits, such as avocado, can be correlated with fleshfirmness and other rheological properties. However, there remains a paucity of information on not only thepostharvest changes in texture of avocado fruit from different origins, but also on the spatial variation in texturewithin individual fruit. In addition, the relationship between changes in texture and lipid profile of fruit tissueduring postharvest ripening is unknown.The aim of the present study was to assess and discriminate between avocado cv. Hass fruit from threedifferent origins (viz. Spain, Peru and Chile) on the basis of temporal and spatial changes in both texture andfatty acid profiles of fruit flesh. Texture of different horizontally-cut slices from individual fruit within aconsignment was measured during ripening using a previously unreported technique. Maximum load, elasticityand viscosity of fruit tissue was measured using an Instron 5542 universal testing machine fitted with either a500 N or 5 N load cell. The same fruit slice was immediately snap-frozen in liquid nitrogen and freeze-driedprior to subsequent extraction, identification and determination of fatty acid methyl esters (FAME) profiles usinggas chromatography coupled to flame ionization detection (GC-FID). The results were used to differentiate avocado fruit into definable groups using partial least squares discriminant analysis. Significant differences inmaximum load, elasticity, viscosity were found in avocado fruit flesh during ripening, and between origins andto a lesser extent between different locations within the fruit. Lipid profiles showed dissimilar compositionaccording to origin and changed slightly from apex to base. The textural changes and lipid profile in avocadofruit is therefore related to origin and the spatial variation within individual fruit.