Effects of postharvest handling on nutritional quality of pomegranate (Punica granatum) Arils

O'Grady, Lizanne (2012-12)

Thesis (MScFoodSc)--Stellenbosch University, 2012.

Thesis

ENGLISH ABSTRACT: The aim of this study was to investigate the effects of storage temperature and duration on the proximate composition, physico-chemical properties and selected bioactive components (vitamin C, anthocyanins and β-carotene) of arils from three pomegranate cultivars (‘Arakta’, ‘Bahgwa’ and ‘Ruby’). Pomegranates were hand-peeled and stored at three different temperatures (1°, 4° and 8°C) at 95% relative humidity (RH) for 14 days, with an additional day at ambient conditions (~21°C). Physico-chemical attributes, anthocyanins, ascorbic acid and proximate composition was measured on day 0, 7, 14 and 15. O2 consumption and CO2 production increased at elevated temperatures. No visual mould growth was detected in ‘Arakta’ and ‘Bahgwa’ arils after 14 days at 1°C 95% RH and after 7 days at 4°C 95% RH. Higher storage temperature negatively affected the proximate composition, physico-chemical attributes and bioactive components. The physico-chemical properties and selected bioactive components (anthocyanins, ascorbic acid, β-carotene) of pomegranate arils (‘Arakta’, ‘Bahgwa’ and ‘Ruby’) packed in three punnets made of polyethylene terephthalate (PET1 - clampshell; PET2 - tub and lid) or polypropylene (PP - tub and lid) material were studied for a period of 14 days at 5°C 95% RH. Packaging did not have a major effect on the physico-chemical and bioactive components of pomegranate arils, although PET2 had relatively stable headspace gas composition within the punnets. Storage duration caused a rise in pH and a decline in titratable acidity irrespective of packaging type. No visual mould growth was detected in ‘Arakta’ arils after 7 days irrespective of the type of packaging, while mould growth was detected in all ‘Ruby’ in all types of packaging. The earlier onset of visual microbial growth lead to a baseline microbiological study evaluating the effect of pre-storage water dipping of whole fruit on the microbiological quality of pomegranate arils stored for 8 days at 5°C 95% RH. Freshly harvested pomegranate fruit (‘Bahgwa’) were dipped in distilled water and air-dried (dipped fruit) or stored without postharvest dipping (dry fruit) at 7°C 95% RH for 15 weeks. Arils were extracted, packaged and stored at 5°C 95±8.34% RH for 8 days. Total viable aerobic mesophillic bacteria, yeasts and moulds, Escherichia coli and Staphylococcus aureus were enumerated. After 8 days at 5°C 95% RH no microbial growth was detected on arils from ‘dry fruit’, while ‘dipped fruit’ showed increased yeast and mould counts (4.74 log cfu.g-1) and total viable aerobic mesophillic bacteria count (3.73 log cfu.g-1). In conclusion storage temperature affects the nutritional quality of pomegranate arils and is best maintained at 1°C for 14 days or 4°C for 7 days at 95% RH. Current South African packaging used to market pomegranate arils don’t have a major effect on the nutritional quality of pomegranate arils, although the headspace gas composition was most stable in PET2 packaging. Pre-storage water dipping of whole pomegranates should be avoided as this could reduce the shelf life of extracted pomegranate arils.

AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die gevolge van bergingstemperatuur en -tydperk op die proksimale samestelling, fisies-chemiese eienskappe en geselekteerde bio-aktiewe komponente (vitamien C, antosianiene en β-karoteen) van granaatpitte van drie kultivars ('Arakta’, ‘Bahgwa’ en ‘Ruby’) te ondersoek. Granaatpitte is geberg by drie temperature (1°, 4° en 8°C) 95% RH vir 14 dae plus ‘n addisionele dag by kamertemperatuur (~21°C). Fisies-chemiese eienskappe, antosianiene, askorbiensuur en proksimale samestelling is gemeet op dag 0, 7, 14 en 15. Die granaatpitte se O2-verbruik en CO2-produksie het toegeneem by hoër bergingstemperature. Geen swamgroei was sigbaar na 7 dae by 1°C 95% RH sowel as 14 dae 4°C 95% RH. Hoër bergingstemperatuur het die proksimale samestelling, fisies-chemiese eienskappe en bio-aktiewe komponente negatief beïnvloed. Die fisies-chemiese eienskappe en geselekteerde bio-aktiewe komponente (antosianiene, askorbiensuur, β-karoteen) van granaatpitte ('Arakta’, ‘Bahgwa’ en ‘Ruby’) is verpak in drie bakkies vervaardig van polyethyleentereftalaat (PET1 – klamp-bakkie, PET2 – bakkie en deksel) of polipropileen (PP – bakkie en deksel) en bestudeer vir 14 dae by 5°C 95% RH. Heel granate was onderworpe aan 10-14 weke bergingstydperk by 7°C 95% RH voor die granate geskil en verpak is. Die bakkie tipe het nie 'n duidelike uitwerking op die fisies-chemiese en bio-aktiewe komponente van die granaatpitte gehad nie, alhoewel die gas samestelling in die kopspasie van PET2 bakkies relatief onveranderd gebly het. Gedurende die bergingstydperk het die pH gestyg en die titreerbare suur gedaal ongeag die bakkie tipe. Geen visuele swamgroei was sigbaar in ‘Arakta’ granaatpitte na 7 dae by 5°C 95% RH terwyl ‘Ruby’ granaatpitte wel swamgroei getoon het ongeag die bakkie tipe. Die vroeë aanvang van sigbare swamgroei het tot ‘n verdere mikrobiologiese basislynstudie gelei. Die uitwerking van voorbergingswaterdompeling van heel granate is geëvalueer op die mikrobiologiese gehalte van die granaatpitte wat gestoor was vir 8 dae by 5°C 95% RH. Vars ge-oesde ‘Bahgwa' granate is in water gedompel en gelugdroog (gedompelde granate) of glad nie in water gedompel nie (droë granate) en geberg by 7°C 95% RH vir 15 weke. Granate is ontpit, verpak en geberg by 5°C 95±8.34% RH vir 8 dae. Totale lewensvatbare aërobiese mesofilliese bakterieë, giste en swamme, Escherichia coli en Staphylococcus aureus telling is vervat. Granaatpitte van ‘droë granate’ was vry van enige mikrobiese groei na 8 dae. Die ‘gedompelde granate’ het ‘n toename in giste en swamme (4,74 log cfu.g-1) en totale lewensvatbare aërobiese mesofilliese bakterieë (3,73 log cfu.g-1) getoon. Hierdie studie maan dus teen waterdompeling van heel granate voor ‘n bergingsperiode van 10-15 weke. Ten slotte word die voedingswaarde van granaatpitte wel beïnvloed deur ‘n hoër bergingstemperatuur en sal die granaatpitte se gehalte behou word by 1°C vir 14 dae of 4°C vir 7 dae by 95% RH. Die voedingswaarde van granaatpitte word nie beïnvloed deur kommersiële verpakking wat tans in Suid-Afrika gebruik word om granaatpitte te adverteer nie, alhoewel PET2 bakkies se gas samestelling in die kopspasie onveranderd gebly het. Waterdompeling van heel granate voor ‘n verlengde bergingstydperk moet eerder vermy word aangesien dit die raklewe van granaatpitte verminder.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/71973
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