The role of harvest time and maturity, orchard and simulated wind on postharvest quality of 'Triumph' persimmon fruit and the potential of NIR as non-destructive sorting tool

Zanamwe, Pesanai (2014-12)

Thesis (MScAgric)--Stellenbosch University, 2014.

Thesis

ENGLISH ABSTRACT: Production of the South African ‘Triumph’ persimmon grown as a counter season supply to European markets declined from 740 ha in 2008 to 550 ha in 2011 due to, among other factors, quality variation observed when the fruit arrives at the market. Variation in fruit quality affects acceptability, hence profitability. The aim of this study was to investigate the effects of time of maturity (influenced by region and paclobutrazol treatment), stage of maturity at harvest (colour), orchard differences and wind on ‘Triumph’ persimmon storage potential (6.5 weeks at -0.5 oC and after 4 days shelf-life at 20 oC) as well as evaluation of near-infrared spectroscopy (NIRs) as an objective tool to sort fruit of various maturity stages. The first study compared storage potential of fruit from an early region treated with paclobutrazol, an untreated early region and a late region harvested at 4 stages of maturity determined by the Perishable Product and Inspection Services (PPIS) persimmon colour chart. Harvesting South African ‘Triumph’ persimmon at colour group 3 (PPIS colour chart values 5-6 compared to commercial harvest at 4-5) demonstrated the potential to improve fruit storage potential regardless of the maturity time. The second trial compared storage potential of fruit harvested at colour group 3 from 4 orchards on each maturity time in the 2012 season and 5 orchards on adjacent farms in the 2013 season. The results demonstrated that, although harvesting fruit at PPIS colour chart values 5-6 improved the general post-harvest quality, significant quality variation resulting from orchard factors could occur. The third trial investigated the effect of wind on storage potential of ‘Triumph’ persimmon fruit by simulating wind and wind damage by blowing trees for 10 min, shaking trees for 2 min, defoliating half of the trees and twisting fruit stalks. Wind simulations increased soft fruit after cold storage, decreased titratable acidity (TA) and total soluble solids (TSS) after shelf-life and delayed fruit colour development after storage and after shelf-life. The effect of wind simulation and simulated damage on storage potential varied per season and should be studied further in more detail. However, orchard practices that reduce wind power may improve quality of stored ‘Triumph’ persimmon fruit. The fourth trial investigated the possibility of using near infra-red spectroscopy (NIRs) as an alternative or complimentary non-destructive fruit sorting tool. Near infra-red (NIR) spectra were obtained over the wavelength range of 800-2500 nm. Flesh firmness, Sinclair (IQ) firmness, TSS, TA and fruit colour were determined using conventional methods after spectral measurements. All measured quality parameters showed that PPIS colour chart alone may not categorise fruits into precise distinctive maturity stages. NIR calibration and validation models proved that NIRs predicts TSS and fruit colour throughout post-harvest storage of ‘Triumph’ persimmon fruit. In conclusion, this study found that harvesting South African ‘Triumph’ persimmon at PPIS colour chart values 5-6, orchard management for post-harvest quality, reducing wind damage and using NIRs as complimentary maturity indexing tool may improve storage potential of the South African ‘Triumph’ persimmon fruit.

AFRIKKANSE OPSOMMING: Die produksie van Suid-Afrikaanse ‘Triumph’ persimmons om die Europese markte te voorsien gedurende die tyd van die jaar wanneer daar geen vrugte op die mark is nie, het afgeneem vanaf 740 ha in 2008 tot 550 ha in 2011. Een van die faktore wat ‘n rol gespeel het in die afname van produksie is die variërende kwaliteit van vrugte op die mark. Vrugkwaliteit variasie affekteer die bemarkbaarheid van vrugte, en dus winsgewendheid. Die doel van die studie was om die effek van tyd van oesrypheid (soos bepaal deur kleur en beïnvloed deur produksie area en paclobutrazol behandeling), boordvariasie en wind op ‘Triumph’ persimmon opberging (6 weke en 3 dae by -0.5 oC) en rakleeftyd (4 dae by 20 oC) te bepaal. Die studie het ook die geskiktheid van naby-infrarooi spektroskopie (NIRs) as ‘n objektiewe sorteringsinstrument van verskeie rypheidsstadia getoets. Die eerste proef vergelyk opbergingspotensiaal van vrugte uit ‘n vroeë produksie area behandel met paclobutrazol, onbehandelde vrugte uit ‘n vroeë produksie area, en vrugte uit ‘n laat produksie area geoes by 4 verskillende stadia van rypwording soos bepaal deur die Bederfbare Produkte en Inspeksie Dienste (Perishable Product and Inspection Services (PPIS)) se persimmonkleurkaart. Die oes van Suid-Afrikaanse persimmons by kleurkaartgroep 3 (PPIS kleurkaart waardes 5-6 in vergelyking met kommersiële oes by 4-5) het die potensiaal om vrugopbergbaarheid te verbeter onafhanklik van produksie area. Die tweede proef vergelyk opbergbaarheid van vrugte van 4 boorde in elke rypwordings tyd / area (2012 seisoen) en 5 boorde op aangrensende plase (2013 seisoen) wat by kleurgroep 3 geoes is. Die resultate demonstreer dat alhoewel vrugkwaliteit na-oes beter behou word wanneer vrugte by PPIS kleurkaartwaardes van 5-6 ge-oes word, betekenisvolle kwaliteitsvariasie bestaan as gevolg van boordverskille. Die derde proef ondersoek die effek van gesimuleerde wind en windskade op die opbergbaarheid van ‘Triumph’ persimmonvrugte. Dit is gedoen deur bome vir 10 min te blaas met lug met behulp van ‘n kommersiële boordspuitpomp, hard te skud vir 2 min, deur die helfte van die blare te stroop, en deur die vrugstele te wring. Windsimulering verhoog die persentasie sagte vrugte na koueopberging, verminder titreerbare sure (TS) en totale oplosbare vastestowwe (TOVS) na rakleeftyd en vertraag vrugkleurontwikkeling na opberging en rakleeftyd. Die effek van windsimulering en geassosieerde skade op opbergbaarheid het baie gevarieer tussen seisoene en moet verder en in meer detail bestudeer word. Boordpraktyke wat windkrag verminder mag egter ‘n verbetering in die kwaliteit van ‘Triumph’ persimmonvrugte tot gevolg hê. Die vierde proef bestudeer die geskiktheid van NIRs as ‘n alternatiewe of aanvullende niedestruktiewe vrugsorteringsapparaat. NIR spektra is ingesamel tussen 800-2500 nm. Fermheid, Sinclair (IQ) fermheid, TOVS, TA en vrugkleur is bepaal deur konvensionele metodes na spektrale metings. Alle vrugkwaliteitsparameters het gewys dat die PPIS kleurkaart nie alleen die vrugte in presiese rypheidsklasse kan indeel nie. NIR kalibrasie en validasie modelle bewys dat NIRs TOVS en vrugkleur ‘Triumph’ persimmon na-oes kwaliteit kan voorspel. In gevolgtrekking het die studie bevind dat die oes van Suid-Afrikaanse persimmonvrugte by PPIS kleurkaartwaardes van 5-6, boordbestuurspraktyke vir die behoud van na-oes kwaliteit, windskade vermindering en die gebruik van NIRs as ‘n aanvullende rypheidsindekseringsapparaat die opbergingsvermoë van Suid Afrikaanse ‘Triumph’ persimmons mag verbeter.

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