Thesis submitted in fulfilment of the requirements for the degree
Master of Technology: Food Technology
in the Faculty of Applied Sciences
at the Cape Peninsula University of Technology / The aim of this study was to evaluate bambara groundnut [BGN] non-starch polysaccharides
[NSP] subject to the incorporation into model and food systems with a view to establish their
functional and physicochemical properties.
BGN insoluble dietary fibre [BGNIF] and soluble dietary fibre [BGNSF] were
successfully extracted from four varieties (black-eye: BLE, red: RED, brown: BRN and
brown-eye: BRE). Physicochemical properties evaluated revealed the high bulk density of all
BGNIF and BGNSF varieties, which could contribute to cost-effective packaging. The
microstructures of BGNIFs were irregular in shape with different sizes. The colour
parameters (lightness, redness, yellowness, chroma and hue angle) differed significantly [p ≤
0.05] across all BGNIF and BGNSF varieties; and indicated a yellowish-red colour for
BGNIFs and a light yellow colour for BGNSFs. Negligible amounts of condensed tannins
[CT] were found in BGNIFs (0.014 – 0.160 mg.g-1). Higher amounts polyphenols [PP] were
present in BGNSFs (45.42 – 55.90 mg.g-1 gallic acid equivalents [GAE]) compared to the
amount PP in BGNIFs (6.14 – 15.56 mg.g-1 GAE). Major sugars identified were
arabinose/galactose, xylose and mannose in BGNIFs, and xylose and mannose in BGNSFs.
The functional properties evaluated revealed high swelling capacity of BGNIFs (6.37 – 7.72
ml.g-1) and no significant [p > 0.05] difference in water retention capacity. Fat absorption
capacity ranged from 1.38 – 1.52 g oil.g-1 dry weight for BGNIFs and 4.04 – 4.55 g oil.g-1 dry
weight for BGNSFs. Variability in BGNIF (91.2%) and BGNSF (79.4%) physicochemical and
functional properties could both be explained by two principal components (BGNIF
component 1: PP, redness, yield; and component 2: xylose, yellowness and chroma; BGNSF
component 1: yellowness, chroma, mannose content; and component 2: redness, fat
absorption and fructose content).
Following an IV optimal mixture design, an optimum white bread formulation was
obtained using 59.5% water, 4.3% yeast and 8.5% BGNIF. Bread enriched with the four
BGNIF varieties (BLE, RED, BRN and BRE) were tested for several physicochemical
properties. Significant [p ≤ 0.05] differences existed between the control and BGNIF
enriched loaves for crumb grain characteristics (including pore area distribution, feret angle,
circularity, roundness and aspect ratio). Specific loaf volume of BGNIF enriched loaves
ranged from 3.33 – 3.85 ml.g-1 and were significantly [p ≤ 0.05] lower compared to the control
bread (4.16 ml.g-1). Favourable texture characteristics obtained with the BGNIF enriched
breads were lower hardness, chewiness and gumminess compared to the control loaf. Crust
and crumb colour parameters (lightness, redness, yellowness, chroma and hue angle) were
significantly [p ≤ 0.05] different across all loaves. BRE BGNIF bread (3.43 ± 0.20) had the
significantly [p ≤ 0.05] lowest crumb colour difference compared to the control bread; whilst
BRN (1.72 ± 0.42) and BRE (2.44 ± 0.78) loaves had the lowest significant [p ≤ 0.05] crust colour difference compared to the control. Favourable chemical properties were the high
total dietary fibre [TDF] (7.14 – 8.33%) content of all BGNIF enriched loaves compared to the
control loaf (4.96%). Significant [p ≤ 0.05] differences were also observed for some loaves
for moisture content, condensed tannins and polyphenol content. Variability in bread
physicochemical properties was differentiated by three components (component 1: bread
textural properties; component 2: specific loaf volume and bread lightness; component 3:
crumb colour parameters) which accounted for a cumulative variation of 92.8%. All bread
loaves were also sensorially acceptable as rated moderately like to like very much (>3 rating
on a 5-point hedonic scale) by consumers for all parameters (appearance, crust and crumb
colour, aroma, taste, texture and overall acceptability) evaluated.
Furthermore, brown BGNSF was tested for stabilising effects in an orange beverage
emulsion. BGNSF and orange oil were varied at two levels each based on a 22 augmented
factorial design and the effects determined on the equilibrium backscattering [BS] flux as
emulsion stability indicator. The BS profiles which resulted from the Turbiscan stability
analysis revealed flocculation at low rates as the major destabilisation mechanism. The
optimal formulation producing a stable emulsion was identified as low oil (6%) and high
BGNSF (30%) concentrations. The objective of this study was therefore achieved and
showed that positive physicochemical and functional properties are associated with BGNIF
and BGNSF from black-eye, red, brown and brown-eye varieties. Furthermore, the
incorporation of BGN fibres in white bread and a beverage emulsion was shown to contribute
positive technological properties in these systems.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:cput/oai:localhost:20.500.11838/833 |
| Date | January 2014 |
| Creators | Diedericks, Claudine Florett |
| Contributors | Jideani, Victoria A., Prof |
| Publisher | Cape Peninsula University of Technology |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Rights | http://creativecommons.org/licenses/by-nc-sa/3.0/za/ |
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