Oral processing of heterogeneous foods : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Science at Massey University, New Zealand
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Date
2011
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Massey University
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Abstract
Food manufacturers could potentially benefit from foods designed to influence
mastication and the breakdown of food into a bolus. Mastication and the properties of
the food bolus have been linked to the sensory and nutritional properties of foods. This
research aimed to investigate the mastication and particle size distribution of the food
bolus of heterogeneous food systems, where one food component is combined with
another, with a view to indentifying parameters that influence mastication and the food
bolus. A range of matrices of contrasting physical properties, which were embedded
with peanut pieces of contrasting physical properties, were investigated.
Trials involved serving these heterogeneous foods to subjects standardized by volume
(concluded as the most suitable serving method following an investigation of natural
bite size). Subjects were asked to chew and expectorate the bolus (where the number of
chews and chewing time were recorded) before the matrix of the expectorated bolus was
washed away to isolate the peanut particles, and the peanut particle size distributions
determined using image analysis. A Rosin-Rammler function was fitted to the
cumulative distribution data of each bolus to derive peanut particle size parameters (d50
and broadness (b)).
Results demonstrated that in heterogeneous food systems the presence of one food
component (the matrices) can alter the breakdown of another food component (the
peanuts) embedded inside that matrix. The properties of the matrix influenced
mastication, the rate of peanut particle size reduction, and the spread of the distribution
of peanut particle size inside the matrix, but did not influence the d50 of the peanut
particle size distribution inside the bolus. Peanut properties did not influence
mastication, but influenced the d50 of the peanut particle size distribution, the rate of
particle size reduction, and the retention of peanuts in the bolus. It is postulated that the
properties of the matrices largely influence the probability teeth contact peanut particles
(known as the selection function), and the properties of the peanuts largely influence
particle fracture per chew (known as the breakage function).
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Keywords
Mastication, Food properties, Peanuts