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Title: Determination of water and wheat bran interaction and their effect on dry cereal product
Author: Roozendaal , Hajo
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2012
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Bran is a composite material that is formed from different histological layers of the wheat kernel, and is a by-product of normal milling that, until recently, was mostly used as an animal feed. However, commercial wholegrain flour products are now becoming more widespread, due to widely reported beneficial effects with respect to the risk factors for developing several chronic diseases (e.g. diabetes, cardiovascular diseases and certain cancers). These effects are thought to be linked not only with the wholegrain dietary fibre, but also with the range of bioactive compounds present in the wholegrain. Unfortunately, the incorporation or fortification of cereal based fibres into white flour-based products is fraught with complications and poses significant technological problems for food manufacturers due to the multi› faceted functional properties of cereal bran leading to undesired effects on processing ability and end-product quality. Bran tends to be highly hygroscopic and on addition to a formulation results in a need for additional water to be added in order to compensate. On the other hand, bran has a low affinity for water and this results in it releasing most of its absorbed water "., when placed under stress (mechanical, gravimetrical or heat), hence causing its undesirable side effects. Although many studies have been performed on the inclusion of bran into a wide range of cereal based products, the cereal wafer baking area has being largely overlooked in research, probably due to the very nature of the application of wafers as a carrier base for the addition of other ingredients. As wafers originate from a wet batter formulation, additional water needs are often masked in the wet stage of processing. However, because of the bran having a low affinity for water, it will readily release water during the baking stage, due to heat stress, decompartmentalising and re-equalizing the amount of water present in the system. There would be apparently no additional water need in the system as normally seen in, for example, bread or cookies, but shelf life is still impacted and reduced, and sensory properties influenced. Therefore, bran from different millstreams and wheat origin were selected and investigated for their rehydration kinetics (wettability) properties, water holding and binding capacity in relation to mill stream and particle size. Also investigated was their ability to release water during heating (thermo gravimetric analysis) when wheat bran was suspended in wheat flour suspension. Further investigations looked into the effect of enzymatic treatment of wheat bran on its rehydration kinetics and thermo gravimetric drying characteristics and finally incorporation of wheat bran into a wafer and its effect on shelf life were investigated. The rehydration kinetics and the water holding and water binding parameters of bran particles in relationship to their mill stream origin and selection, showed that selections of bran particle size and millstream choice, combined with product production parameters, are important factors for consideration in the cereal industry and is therefore dependent on the end product needs. Thermo gravimetric analysis showed that bran has a high degree of influence their surroundings when incorporated into a cereal product. Bran disrupts the water distribution in the system, particularly with respect to functionally important components like starch and gluten. It was shown that incorporating bran up to 25% is the most critical stage of bran addition to a cereal based product, after which any subsequent addition does not have a major incremental impact. Enzymatic digestion of hemicelluloses and cellulose affects the surface of the bran particles, where the bran particles are broken due to the effect of grinding and therefore have the highest concentration of easy to reach hemicellulose and cellulose material. As a result, enzymatic digestion has the greatest effect on the first peak in deconvoluted thermograms observed via thermo gravimetric analysis, reducing the amount of water release associated with this peak. The incorporation of bran into plain wafers, showed significant changes to the wafer in both the shelf life and the individual perception of the samples. Both changes in the textural analysis of the wafers in relationship to their hardness (force) and fractureability (distance) and the headspace volatile compound analysis were determined. Staling was observed via texture analysis, which showed a weakening in the fld ratios, and by an increase in hexanal with onset points between the 4th to th month. Sensory investigations showed that particular attributes, like cardboard (stale) increased in all the bran incorporated wafers, with the malted milk, sweetness and toasted cereal decreasing. The oral and audio perception saw a decrease in cardboard (opposite to brittle), indicating that the wafers are losing cohesive structure, which is stronger in the freshly produced wafers than in the aged wafers.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available