SUNScholar - Browsing by Author "Huysamer, M."

Browsing by Author "Huysamer, M."

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Berry abscission in vitis vinifera L. cv. Waltham Cross : changes in abscission-related factors during berry development
(South African Society for Enology and Viticulture, 2005) Burger, D. A.; Jacobs, G.; Huysamer, M.; Taylor, M. A.
During the 1999 season, changes in total soluble solids (TSS), titratable acids (TA), pedicel diameter, berry diameter, berry mass and fruit removal force (FRF) were determined at biweekly intervals from 27 until 111 days after full bloom (DAFB) for Waltham Cross table grapes. In addition, at each assessment stage, grape bunches were detached and held in the dark at about 25°C for 80 h. Thereafter, moisture loss, FRF, berry abscission potential as well as percentage berry abscission were determined. During stages I and II of fruit growth (27 to 54 DAFB), TSS did not change significantly, while TA increased. FRF increased significantly during this early stage of berry development, indicating a strengthening of the abscission zone tissue. During stage III (after 54 DAFB), a decline in FRF occurred, which coincided with a perceptible increase in TSS and a decrease in TA. Berry mass increased significantly from 27 to 111 DAFB. Pedicel diameter only increased significantly for the period 27 to 41 DAFB, while berry diameter increased significantly for the period 27 to 97 DAFB. Grapes sampled at 27 DAFB had a significantly lower FRF and significantly higher levels of berry abscission and moisture loss after the 80-hour period in the dark, compared with grapes sampled at a later stage. At 27 DAFB, the abscission zone developed between the pedicel and the rachis, thereafter it developed between the pedicel and the berry. Although FRF did not change significantly as berries ripened (from 83 to 111 DAFB), abscission potential and percentage berry abscission were significantly higher for grapes harvested at 83 DAFB at a TSS of 12.3°Brix than for grapes harvested more mature, at a higher TSS. Moisture loss correlated significantly (P<0.0001) with berry abscission, with a correlation coefficient of 0.84. Berry abscission also correlated significantly (P<0.0001) with abscission potential, pedicel and berry diameter, FRF (at sampling), FRF (after 80 h) and berry mass, but not with TSS or TA.
The effect of fruit maturity and storage duration on friction discolouration of Packham's Triumph and Doyenne du Comice pears
(International Society for Horticultural Science -- ISHS, 2005-04) Burger, G. E.; Griessel, H. M.; Huysamer, M.
Friction discolouration (FD) is causing the South African pear industry multi-million rand losses due to blemished fruit being rejected for the export market and being sold locally. The occurrence of FD was studied over two seasons using ‘Packham’s Triumph’ and ‘Doyenne du Comice’ (Pyrus communis) fruit. The influence of fruit maturity and storage duration were investigated by harvesting over three maturities and storing fruit for up to three months. FD was induced using a modified laboratory shaker that was shown to closely mimic pack line damage. Polyphenol oxidase (PPO) activity and total phenolics (TP) content were also evaluated. ‘Doyenne du Comice’ was more prone to FD than ‘Packham’s Triumph’. Harvest maturity significantly influenced FD susceptibility, with the middle picking maturity generally giving higher FD ratings. Increasing storage duration generally increased FD ratings, although not consistently. PPO activity was not influenced by harvest maturity, but was influenced by storage duration. In ‘Packham’s Triumph’, the TP content was not affected by harvest maturity or storage duration, whereas both these factors significantly influenced TP content in ‘Doyenne du Comice’. Susceptibility to development of FD symptoms is not easily linked to either PPO activity or TP content, and seasonal differences in susceptibility make prediction of possible levels of FD very difficult.
Extension of the storage life of plums (Prunus salicina) using controlled atmosphere shipping
(International Society for Horticultural Science -- ISHS, 2005-06) Mare, L.; Truter, A. B.; Kemp, A. T.; Dodd, M. C.; Holcroft, D. M.; Huysamer, M.
South Africa is an important supplier of stone fruit to the northern hemisphere in the months of November to March. The voyage by sea to the main markets in the UK and Continental Europe necessitates production of cultivars that are able to maintain an acceptable eating quality for a period of at least four weeks from the time of harvest. Four Japanese plum (Prunus salicina) cultivars were examined with the view to extend their storage life under regular atmosphere (RA) conditions at -0.5°C following either RA or controlled atmosphere (CA) shipping, using either the commercial dual temperature (-0.5°C, 7.5°C, -0.5°C) or a single high temperature (7.5°C) regime. The cultivars included the locally bred ‘Sapphire’, ‘Songold’ and ‘Laetitia’ as well as ‘Angeleno’ which is well known in plum producing countries internationally. Storage life of all four cultivars could be extended for an additional two to three weeks under RA conditions at -0.5°C without adverse effects on quality, provided that CA was applied during the shipping phase, either under the dual or single high temperature regimes. Fruit firmness was best retained under CA (dual temperature) conditions. These fruit also showed the lowest respiration rates, ethylene production rates and internal ethylene content. Skin colour development was better under single high than under dual temperature conditions, and also better under RA than CA shipping.
The influence of storage duration and elevation of storage temperature on the development of berry split and berry abscission in vitis vinifera L. cv. Thompson seedless table grapes
(South African Society for Enology and Viticulture, 2005) Burger, D. A.; Jacobs, G.; Huysamer, M.; Taylor, M. A.
Thompson Seedless grapes, packed in non-perforated low density polyethylene bags, were cold stored at -0.5°C and RH 83% for 0, 1, 2, 4 and 8 weeks. After storage at -0.5°C for these periods, the grapes were stored for another 2 or 5 days at -0.5°C , or the grapes were transferred and stored at 10°C and RH 88% for 2 or 5 days. The polyliners were kept closed during the different storage periods. Fruit quality examinations were conducted after the specified periods at -0.5°C, and after each additional 2 and 5 days at both temperatures. Berry split increased with prolonged storage at -0.5°C. A linear function (y = 0.58x - 1.14; R2 = 0.97) described this increase in berry split over 61 days storage at -0.5°C. Transferring the grapes from -0.5°C to 10°C resulted in a further increase in berry split. Grapes stored for 0, 1, 2 and 4 weeks at -0.5°C followed by 5 days at 10°C, showed a significant increase in berry split, compared with grapes stored only at -0.5°C for the same period. Although significant differences in berry abscission occurred, no definite trend was observed that could be ascribed to storage period at -0.5°C or to an elevation in storage temperature from -0.5°C to 10°C.
Mealiness of Forelle pears - Quo vadis
(International Society for Horticultural Science -- ISHS, 2005-04) Crouch, E. M.; Holcroft, D. M.; Huysamer, M.
‘Forelle’ (Pyrus communis), a late season blushed pear cultivar grown in South Africa, requires a minimum of 12-weeks cold storage (-0.5 °C) to ripen evenly. Mealiness, a dry texture disorder, may develop at this time. In contrast to other pear cultivars, longer cold storage periods result in less mealiness. This could be related to insufficient total ACC build up and ethylene production, during the first 12 weeks of cold storage, for juicy texture development, during ripening. ‘Forelle’ pears were stored for 3 weeks at -0.5°C, treated with ethylene (100 μL L-1, 24h, 20°C), stored at 20°C for 2 days and thereafter 3 weeks at -0.5°C. Ethylene treatment led to an increase in mealiness after this period. However there were no differences in treated and control fruit following further ripening at 15°C for 7 days. Mealiness could not be linked to insufficient ethylene during shorter storage periods. Harvest maturity, a factor known to influence mealiness, was tested by harvesting fruit 2 weeks prior to commercial harvest, during commercial harvest, and 2 and 4 weeks after commercial harvest. Mealiness occurred at all harvest dates after 6 weeks at -0.5°C and 7 days at 15°C. Storage temperature was also tested as another factor influencing mealiness. Fruit were stored at -0.5°C, 4°C and 7.5°C for 6 weeks and ripened for 7 days at 15°C. Fruit stored at 4°C and 7.5°C ripened with 0 and 8% mealiness, respectively, in contrast to 70% in control fruit. Results could, however, not be confirmed in 2002 and 2003 as all treatments exhibited low mealiness levels (<4%). As high temperatures prior to harvest may influence mealiness, overhead evaporative cooling was applied during 2003 from early fruit development or from 2 weeks prior to harvest. Little to no mealiness developed in all treatments making it difficult to conclude if cooling prior to harvest affects mealiness.
Postharvest calyx retention of citrus fruit
(Acta Horticulturae, 2005-06) Cronje, P. J. R.; Crouch, E. M.; Huysamer, M.
Abscission is an active developmental process occurring at the abscission zone of the fruit peduncle. The target cells in the abscission zone, which are involved in the process of separation, are located in the separation layer, which is organized in a few cellular layers. In general, it is accepted that the increase in ethylene production in the fruit is followed by increased sensitivity of these cells to ethylene, which would lead to abscission. The abscission process is divided into two phases with respect to sensitivity to auxin and ethylene. The auxin, 2,4-D (2,4-dichlorophenoxy acetic acid), has been used as a postharvest packhouse treatment to retard calyx abscission (to repress postharvest decay). Commercially the sodium salt 2,4-D (Deccomone®) is applied to the fruit in a dip treatment at 500 ppm. The aim of this experiment was to test three agrochemicals (aminoethoxyvinylglycine (AVG), 1-naphthylacetic acid (NAA) and 1-methylcyclopropene (1-MCP)) that could possibly replace the postharvest application of the auxin 2,4-D. AVG had a fruit firming effect but no significant effect on calyx retention. NAA resulted in a high percentage of abscission, probably due to auxin overdose. The 1-MCP at low concentrations of 100 ppb and 250 ppb resulted in calyx retention but had a desiccating effect on the calyx whereas at a high concentration of 500 ppb there was a significant increase in calyx abscission. There was no loss of internal quality or colour. To conclude, according to what is known about the role of ethylene in abscission, 1-MCP and AVG should have prevented abscission of the calyx. Unfortunately, the results show that this complex plant mechanism is not so readily manipulated and 2,4-D remains the best product to inhibit calyx abscission of citrus fruit.
Status of the pear industry in Africa, with specific reference to South Africa
(Acta Horticulturae, 2005-04) Ferrandi, C. H.; Van der Merwe, P. W.; Huysamer, M.
In the context of global production, Africa as a continent is a very small producer of Pyrus communis pears, with roughly 3% of global hectares and production. South Africa produces 56% of Africa’s total crop, followed by Algeria (16%), Tunisia (11%), Egypt (9%) and Morocco (8%). With the exception of very small volumes at high elevations in Kenya and Zimbabwe, production is located around 33-35° north and south of the equator. Since the early 1980’s, plantings in South Africa have increased from approximately 7 000 to 13 000 hectares. The main cultivars are ‘Packham’s Triumph’, ‘Bon Chrétien’, ‘Forelle’, ‘Rosemarie’ and ‘Beurre Bosc’. Planting densities have increased from 740 trees per hectare in 1980 to an average of 1 746 trees per hectare in 1995. Roughly 45% of the current orchards are on clonal BP1 and BP3 rootstocks with the remaining, mainly older, orchards on seedling rootstocks. About 38% of the production is packed for export, 44% used for processing (canning and juice) and 18% for local fresh market consumption. Exports have increased from approximately 6 million cartons (12.5 kg) in 1990 to 10 million cartons in 2003. The continental EU accounts for approximately 45% of exports, followed by the United Kingdom (41%), Far East (8%), North America (3%), Middle East (2%) and Africa (1%). The pear industry in South Africa experienced a ‘golden era’ in the early 1990’s, but has since been struggling to maintain profitability, primarily due to exchange rate fluctuations and the overall worldwide market negativity for deciduous fruit.
Temperature variances in a 12 m integral reefer container carrying plums under a dual temperature shipping regime
(International Society for Horticultural Science -- ISHS, 2005-07) Punt, H.; Huysamer, M.
The South African plum industry is an important supplier of fresh fruit to the northern hemisphere from December to April. Extensive use is made of a dual- temperature shipping regime, which is a form of intermittent warming, in order to limit the occurrence of chilling-related internal defects like gel breakdown (GB) and internal browning (IB). The perception in industry is that use of the 12 m integral reefer containers leads to more quality defects than are experienced in conventional reefer vessels using the same temperature regimes. It was hypothesised that there are significant temperature variances in the integral reefers and three pallets of Sapphire plums were therefore wired with thermocouples to log pulp and air temperatures during commercial shipping to the United Kingdom. Results indicated that the delivery air temperature (DAT) was very close to the set point, and that the container therefore had the refrigeration capacity to maintain the DAT within acceptable tole- rances. Air temperatures within the pallets, however, varied significantly, with peaks of up to 12°C at a set point of 7.5°C. The fruit pulp temperatures showed similar deviations. As expected, fruit in the pallet closest to the doors showed the slowest reaction to changes in temperature, and those in the pallet closest to the cooling unit, the most rapid. Fruit in the 4th layer on the pallet, closest to the base of the pallet, reacted fastest to changes in set point, and fruit in the 10th layer, close to the middle of the pallet, generally reacted the slowest. All fruit were deemed ‘ripe and ready to eat’ upon arrival, and no IB ir GB were found. Mention was made, however, of significant levels of shrivel, which may have been aggravated by the fairly low relative humidity in the container. Further trials are underway to investigate the relationship between fruit quality and the temperature gradients in reefer containers, using cultivars with differing metabolic rates.

Browsing by Author "Huysamer, M."

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