Yasar Karakurt

The influence of foliar and soil fertilization of humic acid on yield and quality of pepper

Abstract Humic acid (HA) is the result of organic matter decomposition and is beneficial to plant growth and development. The objective of the study was to find the influence of foliar and soil HA application on fruit quality and yield of organically grown pepper. Pepper plants were treated with soil and foliar HA applications at various concentrations (0 ml/l, 10 ml/l, 20 ml/l, 30 ml/l, and 40 ml/l). Starting four weeks after planting, HA was applied via spraying and/or drenching to the plant root area three times during the growth period at 15-day intervals. HA treatments had no significant effect on fruit firmness, fruit length, or diameter. Total and reducing sugar contents significantly increased in response to both foliar and soil HA treatments. Moreover, HA application significantly influenced total chlorophyll content and this effect was mainly on chlorophyll b content. Foliar 20 ml/l and soil 20 ml/l HA application resulted in the highest total chlorophyll content. Foliar and soil HA applications also led to significantly higher mean fruit weight, and early and total yield than for control. The study demonstrates that both soil and foliar HA treatment might successfully be used to obtain higher fruit yield and can significantly enhance fruit quality in organically grown pepper.

Cell wall modification in 1-methylcyclopropene-treated post-climacteric fresh-cut and intact papaya fruit

Papaya is a climacteric fruit in which ripening is greatly regulated by ethylene often associated with stress responses such as wounding. The changes in cell wall compositions in papaya fruit at an advanced stage of ripening under stress conditions including chilling temperature of 5°C and wounding employed as fresh-cut and how these changes were affected by an ethylene action inhibitor of 1-methylcyclopropopene (1-MCP) were examined in the study. The recovery of ethanol-insoluble solids, total soluble sugars, water-soluble polyuronides, neutral hemicelluloses, and neutral sugars of rhamnose, arabinose, mannose and glucose were not affected by 1-MCP or fresh-cut processing. The fresh-cut processing, however, caused a higher loss of total polyuronides and the neutral sugar galactose while increasing the recovery of chelator-soluble polyuronides. Few significant differences due to 1-MCP application were recorded in the recoveries of alkali-soluble polyuronides, hemicellulosic polyuronides extracted with 4% KOH, and the neutral sugar xylose. Modifications of cell wall polyuronides and hemicelluloses in ripe fresh-cut papaya fruit exhibited mostly similar patterns to those in intact ripe papaya fruit under the chilling temperature of 5°C while minimally affected by 1-MCP.

Early Harvest Effects on Hydrophilic Phenolic Components of Extra Virgin Olive Oils Cvs. ‘Ayvalık,’ ‘Memecik,’ and ‘Topakaşı’

The study was conducted to determine the effects of cultivar, harvest period, and their interaction on the hydrophilic phenolic components extra virgin olive oils of the cultivars ‘Ayvalık,’ ‘Memecik,’ and ‘Topakaşı.’ Olives were collected at three different harvesting periods: (1) early harvest period-1 (Beginning of spotting), (2) early harvest period-2 (End of spotting), and (3) optimum harvest period. Oils were extracted using the Abencor system. HPLC (High-performance liquid chromatograph) technique was used to quantify the phenolic compounds including tyrosol (p-HPEA), hydroxytyrosol (3,4-DHPEA), luteolin, rutin, quercetin, catechin, sinapinic acid, p-coumaric acid, cinnamic acid, vanillin, vanillic acid, ferulic acid, and gallic acid. The results indicated that the effects of harvest period on the phenolic components were variety dependent. At the early harvest period-1, ‘Memecik’ and ‘Topakaşı’ had the highest efficiency in luteolin, cinnamic acid, vanillic acid, and ferulic acid contents, while ‘Ayvalık’ had the highest efficiency in hydroxytyrosol, sinapinic acid, p-coumaric, vanillin, and ferulic acid contents. At the optimum harvest period, ‘Ayvalık’ had the highest efficiency in luteolin, tyrosol, and gallic acid contents, while ‘Topakaşı’ had the highest efficiency in tyrosol, hydroxytyrosol, and rutin content. The highest phenolic content was detected in the early harvest period-1. The content of tyrosol linearly increased with the progress of maturity harvest period, whereas the contents of the sinapinic acid, vanillin, vanillic acid, and ferulic acid decreased. The oils of ‘Memecik’ variety had significantly higher phenolic content than those of ‘Ayvalık’ and ‘Topakaşı’ varieties.