Thesis (MScFoodSc)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Perforation-mediated modified atmosphere packaging (PM-MAP) offers the possibility of optimising polymeric films in order to compensate for barrier limitations of conventional modified atmosphere packaging (MAP). The aim of this study was to investigate the effects of PM-MAP and storage duration on the physico-chemical quality attributes, microbial quality, phytochemicals (anthocyanins, phenolics and ascorbic acid) and antioxidant activities of arils from fresh minimally processed pomegranate (cv. Acco). The effects of number of perforations (0, 3, 6 and 9; Ø = 0.8 mm) and storage temperature (5, 10 and 15 ºC) on water vapour transmission rate (WVTR, g/m2.day) of synthetic ‘Polylid’ and biodegradable (Nature flexTM) polymeric films were investigated. The results showed that non-perforated biodegradable film had higher WVTR at all storage temperatures, and irrespective of film type, increasing the number of perforations (from P-3 to P-9) had higher impact on WVTR than increasing storage temperature (from 5 to 15 ºC).
Furthermore, this study investigated the effects of PM-MAP on the physico-chemical properties, phytochemicals components and antioxidant activities of fresh minimally processed arils. Arils (100 g) were packaged in polypropylene trays (10.6 x 15.1 cm2) and heat-sealed with a polymeric film POLYLID®. Perforations (0, 3, 6 and 9; Ø = 0.8 mm) were made on the top of the film and all samples were stored at 5 ± 1 ºC and 95 ± 2% relative humidity for 14 days. Samples were analysed at intervals of 3, 6, 9, 12 and 15 days. Microbial analysis included tests for Escherichia coli, aerobic mesophilic bacteria, yeast and moulds at days 0, 6, 10 and 14. The results showed that headspace gas composition was significantly influenced by the number of perforations, which helped balance the decrease in O2 with corresponding increase in CO2 levels, thus preventing anoxic conditions. Total soluble solids, titratable acidity and firmness of arils were slightly reduced by PM-MAP compared to clamshell trays. Colour attributes was generally maintained across all treatments and throughout the storage duration. The highest counts of aerobic mesophilic bacteria (5.5 log CFU/g), yeast and moulds (5.3 log CFU/g) were observed in P-0 and P-9 packages, respectively. Overall, P-3 and P-6 better maintained the physico-chemical properties and microbial quality of arils. Total phenolics and anthocyanin contents were higher in arils packaged in PM-MAP while ascorbic acid was slightly reduced. Antioxidant activities tested against FRAP and DPPH radical-scavenging activity increased across all types of MAP over storage duration. However, antioxidant activities were significantly higher in pomegranate arils packaged in PM-MAP due to O2-promoted biosynthesis of phenolics and anthocyanins which constitute the antioxidant properties.
Overall, the results reported in this study showed that the use of PM-MAP in cold chain could be suitable for the preservation of physico-chemical quality, phytochemical contents and antioxidant properties of arils packaged in passive PM-MAP compared to clamshell and non-perforated packages during postharvest handling and storage. Perforating MAP films showed potential in preventing the incidence of in-package moisture condensation which is a common problem during postharvest handling and storage of fresh produce packaged inside non-perforated MAP. The results also showed the importance of keeping PM-MAP packs in closed refrigerated shelves to avoid cross contamination or ingress of foodborne pathogens. / AFRIKAANSE OPSOMMING: Perforasie-bemiddelde gewysigde-verpakking (PM-MAP) maak dit moontlik om polimeer films te optimiseer en om sodoende te kompenseer vir die versperring beperkings van die konvensioneel-gewysigde atmosfeer verpakking (MAP). Die doelwit is om die effek van PM-MAP en die duur van stoor op die fisioko-chemiese gehalte kenmerke, mikrobiale gehalte, fitochemikale (antisianien, fenolies en askorbiensuur) en antioksidant aktiwiteite van granaatarils van vars, minimaal geprosesseerde granate, te ondersoek (cv. Acco). Die effek van die aantal perforasies (0, 3, 6 en 9; Ø =0.8 mm) en stoortemperatuur (5, 10 en 15 ºC) op die waterdamp transmissie koers (WVTR, g/m2.day) van sintetiese ‘Polylid’ en biodegradeerbare (Nature flexTM) polymeriese films is ondersoek. Die resultate het bewys dat nie-perforeerde biodegradeerbare film by alle stoortemperature ’n hoër WVTR het, en dat by alle tipes film, ’n verhoogde aantal perforasies (van P-3 tot P-9) ’n hoër impak op WVTR het as ’n verhoogde stoortemperatuur (van 5 tot 15 ºC).
Verder is die effek van PM-MAP op die fisiko-chemiese kenmerke, fitochemikale komponente en antioksidant aktiwiteite van vars, minimaal-geprosesseerde granaatarils bestudeer. Die granaatarils (100 g) is verpak in in polipropilien (PP) platkissies (10.6 x 15.1 cm2) en verseël met polimeer film, POLYLID®. Perforasies (0, 3, 6 en 9; Ø =0.8 mm) is aan die bo-end van die film aangebring en alle voorbeelde is vir 14 dae teen 5 ± 1 ºC en 95 ± 2 % relatiewe humiditeit. Die voorbeelde is met tussenposes van 3, 6, 9, 12 en 15 dae ontleed. Die ontleding het toetse vir Escherichia coli, aerobiese mesofiliese bakterië, suurdeeg en skimmel op tussernposes van 0, 6, 10 en 14 dae ingesluit. Die resultate bewys dat die komposisie van die gas beïnvloed word deur die aantal perforasies. Dit help om die vermindering in O2 met ’n ooreenkomstige toename in CO2 vlakke te balanseer en om dus toestande wat deur ’n gebrek aan suurstof veroorsaak is, te verhoed. Die totaal van oplosbare vaste stowwe, titreerbare suurgehalte en fermheid van die granaatarils is deur die PM-MAP verminder veral as dit vergelyk word met “clamshell trays”. Die kleur kenmerke het oor die algemeen dieselfde gebly by al die behandelings en dwarsdeur die stoortydperk. Die hoogste aantal aerobiese mesofiliese bakterië (5.5 log CFU/g), gis en skimmel (5.3 log CFU/g) is in die P-0 en P-9 verpakkings onderskeidelik opgemerk. Oor die algemeen is P-3 en P-6 beter in staat om die fisioko-chemiese kenmerke en mikrobiale gehalte van die granaatarils te behou. Die totaal van die fenoliese and antosianiin inhoud was hoër in granaatarils wat verpak is in PM-MAP maar die askorbiensuur was effens laer. Antioksdant aktiwiteite is getoets teen FRAP en DPPH aktiwiteite het by al die tipes van MAP tydens stoor vermeerder. Antioksidant aktiwiteite was egter heelwat hoër in granate wat in PM-MAP verpak is. Dit is die gevolg van die biosintese van fenolies en antosianins wat deur O2 in die hand gewerk word en wat die basis van antioksidant kenmerke vorm.
Oor die algemeen toon die resultate van hierdie studie dat die gebruik van PM-MAP in die koue ketting geskik is vir die behoud van fisieko-chemiese gehalte, fitochemiese inhoud en antioksidant kenmerke van granaatarils wat in passiewe MAP verpak is, veral as dit vergelyk word met die vrugte wat in ‘clamshell’ en nie-geperforeerde verpakking tydens hantering na die oes en tydens stoor verpak is. Die perforeer van MAP films kan die voorkoms van die kondensasie in die verpakking verminder. Hierdie kondensasie is ’n algemene probleem tydens die hantering en stoor van vars vrugte wat in MAP sonder gaatjies verpak is. Die resultate toon ook hoe belangrik dit is om die PM-MAP verpakking in toe, verkoelde rakke te hou en om sodoende kruis-kontaminasie asook kontaminasie deur kieme wat in vrugte teenwoordig is, te voorkom.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/96079 |
| Date | 12 1900 |
| Creators | Hussein, Zaharan |
| Contributors | Opara, Umezuruike Linus, Marena, Manley, Caleb, James Oluwafemi, Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | viii, 122 p. : col. ill. |
| Rights | Stellenbosch University |
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