Thesis (MSc Food Sc)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Nectar formulations containing red-fleshed plum pulp and varying amounts of red-fleshed plum skin
extract were developed. Red-fleshed plum nectar formulations containing 0, 8, 16, 24, and 32% skin
extract were benchmarked against twenty-two commercial beverages containing red, violet and blue
fruits. The total soluble solid content, pH, titratable acidity, colour, total polyphenolic, individual
polyphenolic, total anthocyanin, and ascorbic acid contents, as well as antioxidant activity (oxygen
radical antioxidant capacity (ORAC), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity,
and ferric reducing/antioxidant power (FRAP)) of the commercial beverages and plum formulations
were determined. The plum nectar formulations had similar or higher total polyphenolic content,
antioxidant activity, and colour values than the average for the commercial beverages. The individual
polyphenolic compounds analysed in the nectar formulations were cyanidin-3-glucoside, cyanidin-3-
rutinoside, quercetin-3-glucoside, quercetin-3-rutinoside, quercetin-3-xyloside, and neochlorogenic acid.
Increasing polyphenolic content and antioxidant activity was observed with an increase in skin extract
content of the formulations. The sensory attributes of the formulations were plum and plantlike aroma,
plum and plantlike flavour, sweetness, acidity, and astringency. Increases in plantlike aroma and
flavour, acidity, and astringency in conjunction with decreases in plum aroma, plum flavour, and
sweetness extract were observed with an increase in skin extract. Consumer analysis indicated that all
formulations were acceptable. The 0 and 16% skin extract formulations were most preferred, while the
32% skin extract formulation was least preferred. A shelf-life study was conducted in two phases. In
Phase 1, the 0, 16 and 24% skin extract formulations were stored at 0 and 5°C (analysis time points:
before pasteurisation, after pasteurisation (week 0), and after 1, 2, 4, 6, 8, 12, 16, 18, 20, and 24 weeks
of storage). Chemical analyses conducted included colour, total polyphenolic, individual polyphenolic
compound, and total anthocyanin contents, and antioxidant activity (DPPH• scavenging activity).
Results from Phase 1 indicated close associations between the 16 and 24% skin extract formulations,
and between these formulations and all chemical attributes. Regression analysis of results indicated
significant (P 0.05) decreases in red colour, total anthocyanins, cyanidin-3-glucoside, cyanidin-3-
rutinoside, DPPH• scavenging activity, total polyphenolic content, quercetin-3-rutinoside, and quercetin-
3-xyloside for formulations stored at 0°C. The total and red colour, total anthocyanins, cyanidin-3-
glucoside, and cyanidin-3-rutinoside in formulations stored at 5°C showed similar results. During Phase
2 of the shelf life study, sensory analysis was conducted on the 0 and 24% skin extract formulations
stored at 5°C (preparation time points: 0, 1, 2, and 3 months). Sensory attributes, including plum,
plantlike, and raisin flavour, sweetness, acidity, and astringency, were stable during storage. Chemical
results from Phase 2 were similar to those of Phase 1. The chemical and sensory stability of
formulations after 24 weeks of storage in Phase 1 and Phase 2 indicated that, with the exception of the
anthocyanin degradation, the formulations could be beneficial to juice industries. Thus, red-fleshed
plum nectars have the potential to compete with high-antioxidant fruit beverages. / AFRIKAANSE OPSOMMING: Nektarformulasies wat rooivleis pruimpulp en varieërende hoeveelhede rooivleis pruimskilekstrak bevat,
is ontwikkel en ondersoek. Rooivleis pruimnektarformulasies wat 0, 8, 16, 24, en 32% skilekstrak bevat,
is vergelyk met twee-en-twintig kommersiële drankies wat rooi, violet en blou vrugte bevat. Die totale
oplosbare vastestof, totale polifenoliese, individuele polifenoliese, totale antosianien- en askorbiensuur
inhoude, sowel as die pH, titreerbare suurheid, kleur, antioksidant aktiwiteit (suurstofradikale
antioksidantkapasiteit (ORAC), 2,2-difeniel-1-pikrielhidrasiel (DPPH) radikaal blussingsaktiwiteit, en
ysterreduserende/antikoksidantkrag (FRAP)) van die kommersiële drankies en pruimnektarformulasies,
is bepaal. Die pruimnektarformulasies het soortgelyke of hoër totale polifenoliese inhoud,
antioksidantaktiwiteit, en kleurwaardes gehad in vergelyking met die gemiddelde vir die kommersiële
drankies. Die individuele polifenoliese verbindings wat in die nektarformulasies geanaliseer is, was
sianidien-3-glukosied, sianidien-3-rutinosied, kwersetien-3-glukosied, kwersetien-3-rutinosied,
kwersetien-3-xylosied, en neochlorogeniese suur. ‘n Toenames in die kleurwaardes, polifenoliese
inhoud, en antioksidantaktiwiteit is waargeneem met ‘n toename in skilekstrak is in die formulasies. Die
sensoriese eienskappe van die formulasies was pruim- en plantagtige aroma, pruim- en plantagtige
geur, soetheid, suurheid, en frankheid. Toenames in plantagtige aroma en geur, suurheid en frankheid,
sowel as ‘n afname in pruimaroma, pruimgeur, en -soetheid, is met ‘n toename in skilekstrak
waargeneem. Verbruikersanalise het aangedui dat al die formulasies aanvaarbaar was. Die 0 en 16%
skilekstrakformulasies was die mees aanvaarbaarste, terwyl die 32% skilekstrakformulasie die minste
aanvaarbaar geag is. ‘n Rakleeftydstudie is in twee fases gedoen. In Fase 1 is die 0, 16, en 24%
skilekstrakformulasies by 0 en 5°C gestoor (analiseringstydpunte: voor pasturisasie, na pasturisasie
(week 0), en na 1, 2, 4, 6, 8, 12, 16, 18, 20, en 24 weke van berging). Chemiese analise wat gedoen is,
sluit totale polifenoliese, individuele polifenoliese verbinding, en totale antosianien inhoude, sowel as
kleur en antioksidantaktiwiteit (DPPH• blussingsaktiwiteit) in. Resultate van Fase 1 het ‘n nou verband
tussen die 16 en 24% skilekstrakformulasies, sowel as tussen hierdie formulasies en hul chemiese
kenmerke aangedui. Regressie-analise van resultate het betekenisvolle (P 0.05) afnames geïllustreer
in rooi kleurwaardes, DPPH• blussingsaktiwiteit, sowel as totale antosianiene, sianidien-3-glukosied,
sianidien-3-rutinosied, totale polifenoliese, kwersetien-3-rutinosied, en kwersetien-3-xylosied inhoude
van die formulasies wat by 0°C gestoor is. Die totale kleur-, rooi kleurwaardes, sowel as totale
antosianien, sianidien-3-glukosied, en sianidien-3-rutinosied in die formulasies wat by 5°C gestoor is,
het soortgelyke resultate gegee. Gedurend Fase 2 van die rakleeftydstudie is sensoriese analise op die
0 en 24% skilekstrakformulasies wat by 5°C gestoor is, gedoen (voorbereidingstydpunte: 0, 1, 2, en 3
maande). Sensoriese eienskappe, insluitend pruim-, plantagtige-, en rosyntjiesmake, soetheid,
suurheid, en frankheid, was stabiel gedurende berging. Chemiese resultate van Fase 2 was soortgelyk
aan dié van Fase 1. Die chemiese en sensoriese stabiliteit van die formulasies na 24 weke van
opberging in Fase 1 en Fase 2 nieteenstaande antosianienafname, het aangedui dat die formulasies
voordelig kan wees vir die vrugtedrankiebedryf. Dus het rooivleis pruimnektars die vermoeë om met
hoë antioksidant vrugtedrankies mee te ding.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/6861 |
| Date | 03 1900 |
| Creators | Steyn, Naomi |
| Contributors | De Beer, D., Muller, M., University of Stellenbosch. Faculty of AgriSciences. Dept. of Food Science. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 97 p. : ill. |
| Rights | University of Stellenbosch |
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