Massey Documents by Type

Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294

Browse

Start date: 2022Subject: search.filters.subject.Wheat

Search Results

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Insights into wheat grain microstructure and composition for the development of novel flour with slow digestion properties and enhanced functional characteristics : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand
    (Massey University, 2025) Abhilasha
    Wheat has been consumed as whole grains, broken grains, flattened format, and puffed format other than the flour format, which has a wide application in different types of food preparations. Wheat flour possesses a unique ability to form a cohesive dough that has viscoelastic properties. A range of products with wheat as their major ingredient are high glycaemic index (GI) foods as wheat flour contains highly digestible starch. However, the consumption of high GI foods is associated with chronic diseases such as diabetes, coronary heart disease, and obesity due to a rapid increase in blood glucose levels and secretion of insulin. The major objective of the research studies of this thesis included creating slowly digestible flour with improved functionality using slowly digested starch sources and non-starch components. Modifying wheat grain through different processing techniques alters the microstructure, and therefore, starch digestibility is impacted. Microstructure modification through various processing techniques, which can control the access of digestive enzymes to starch, could help develop products with controlled starch digestibility. To advance the understanding of the impact of wheat grain microstructure on starch hydrolysis, Chapter 3 explored a study on whole wheat grain in different commercially available forms (kibbled, cut grains, and flour) to understand the influence of microstructural changes on in vitro starch digestibility. The process of size reduction from raw intact grains to kibbled grains and flour caused an increase in overall starch hydrolysis (%) during simulated digestion in the order of flour>kibbled>cut>intact whole wheat grains. Cooking of these formats further increased their starch hydrolysis. However, both cooked cut and intact grains were low glycaemic with the expected glycaemic indices (eGI) of values of 54.08±0.03 and 41.98±0.04, respectively, revealing the role of intact microstructure in starch hydrolysis of wheat grains. Based on the role of intact microstructure, Chapter 4 investigated the possibility of reducing the starch hydrolysis in wheat grain formats (whole, flakes, and flour) by hydrothermal treatment and low-temperature storage of whole wheat grains. The extent of starch hydrolysis after oral-gastro-small intestinal digestion in vitro was significantly lower (p<0.05) in intact grains, flakes, and flours from the cold-stored grains than their non-cold-stored counterparts. In this study, scanning electron micrographs, pasting properties, water retention capacities, and relative crystallinity of the resulting flours revealed an enhanced degree of gelatinisation with the treatment temperature; however, cold-storage of treated grains resulted in a change in these properties due to the retrogradation of the starch. This study indicates that hydrothermal pre-treatment of grains followed by low-temperature storage for prolonged periods might help to reduce the starch digestibility of wheat grains and their resulting products and could be an effective strategy in developing reduced glycaemic impact grain products. However, in our preliminary trials, the flours from hydrothermally treated and low-temperature stored grains resulted in doughs of inferior viscoelastic properties. Furthermore, intending to create slowly digestible flour, Chapter 5 employed two approaches to modify a resistant starch: one involving soluble extracts from wheat flour and vital gluten (water solubles, salt-assisted water-solubles, and acid-solubles) and the other utilising hydrocolloids (guar gum, xanthan gum, locust bean gum, and carboxymethyl cellulose). Modifications from both approaches resulted in modified starch morphology with the formation of starch clusters mimicking the wheat flour. Moreover, the modification with hydrocolloids resulted in an improved pasting profile. Furthermore, in vitro digestion studies revealed that the starch hydrolysis rate was decreased for most of the cooked modified starches with wheat solubles and a slower starch hydrolysis profile until 60 min of simulated small intestinal digestion for most of the hydrocolloids used, carboxymethyl cellulose being the least effective in slowing the starch hydrolysis rate. Additionally, Chapter 6 evaluates the functionality and starch digestibility of a wheat flour system (dough and flatbread-chapatti) by utilising the modified starches created in Chapter 5 as low glycaemic ingredients. The interaction of the modified starches with vital gluten and wheat flour components resulted in improved viscosity of the functional flour. The microstructure of the functional flour dough indicated that the modified starches with wheat solubles (soluble extracts from wheat flour and vital gluten) and hydrocolloids improved the starch-protein matrix and gluten network. Furthermore, the in vitro digestion study revealed the overall starch hydrolysis of chapattis from all the functional flour formulations was significantly lower than the wheat flour chapatti. In conclusion, structural modifications of wheat grain could help reduce the overall starch hydrolysis of wheat grain products. Moreover, the wheat grain components have the potential to modify resistant starch sources to improve their functionality while retaining their slow digestion property. Also, utilising hydrocolloids to modify resistant starch sources could be an effective strategy to enhance the functionality of resistant starches in wheat-based systems. Modified resistant starches created using wheat solubles (soluble extracts from wheat flour and vital gluten) and hydrocolloids have potential applications with slow digestibility and improved functionality in wheat-based products.
  • Thumbnail Image
    Item
    Value added wheat through applied genomic prediction : a genomic approach for breeding low gluten epitope wheat : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Plant Breeding and Genetics at Massey University, Palmerston North, New Zealand. EMBARGOED until 24 July 2026.
    (Massey University, 2023) Macalister, Jamie
    Gluten epitopes are known to trigger coeliac disease (CD) in affected consumers and are believed to be linked to some cases of gluten intolerance. Research suggests that if consumers were exposed to wheat with reduced concentrations of gluten epitopes, the incidence of CD and gluten intolerance may be reduced. Methods have recently been developed allowing researchers to measure gluten epitope concentrations in wheat. This offers wheat breeders the potential to select towards varieties with lower epitope concentrations than existing cultivars. However, the methods for measuring epitope concentrations remain costly and time consuming. Therefore, it is proposed that a genomic based approach for breeding low epitope wheat lines is a more practical method than traditional phenotype-based selections. The genetic factors associated with epitope concentrations remain poorly understood. In this thesis, heritability estimates of between 0.37-0.93 are reported for concentrations of 6 distinct gluten epitopes. The associations between epitope concentrations and baking quality are also assessed and are shown to range from being near zero for some epitopes to strong positive correlations between other epitopes and particular baking quality characteristics. A Genome Wide Association Study and a model for genomic prediction are employed to determine the genetic factors associated with epitope concentrations. In these analyses, 3 significant genomic windows are identified as being associated with concentrations of 3 particular epitopes. Empirical prediction accuracies of between 0.16-0.53 are observed for predictions of epitope concentrations in a breeding population. Additionally, accuracies of between 0.37-0.67 are achieved by adjusting the population structure to represent the ideal circumstances that breeders would aim to achieve in their training and target populations. These results demonstrate that genomic selection (GS) will be an effective method for breeding low gluten epitope wheat. The outcome of this thesis will allow implementation of GS in the New Zealand Institute for Plant & Food Research wheat breeding program where epitope concentrations will be established as a new breeding target. This is expected to lead to the release of niche, low epitope cultivars with a value-add component that benefits growers, industry and consumers.
  • Thumbnail Image
    Item
    Breakdown of rice and wheat-based foods during gastric digestion and its implications on glycemic response : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand
    (Massey University, 2022) Nadia, Joanna
    The composition and structure of starch-based foods determine their breakdown behavior in the digestive tract and consequently their glycemic response. The glycemic response of starch-based foods is known to be influenced by their gastric emptying rate. However, the role of gastric digestion in regulating this process has not been well-understood, especially on how food breakdown behavior in the stomach may be related to the glycemic response. In this project, the link between food structure, food breakdown during gastric digestion, gastric emptying, and glycemic response was investigated in vivo using a growing pig model. Durum wheat- and white rice-based foods of varying physical structures (semolina porridge, rice- and wheat couscous, rice grain, rice noodle and wheat noodle/pasta) were studied. It was found that the foods with smaller-sized particles (semolina porridge and couscous products) had faster gastric breakdown rate and gastric emptying rate, resulting in higher glycemic impact (maximum change from the baseline and the overall impact) compared to the foods with larger-sized particles (rice grain and noodle products). The faster gastric breakdown rate of the smaller-sized foods was related to their acidification rate in the stomach, which caused their dilution or dissolution by gastric secretions. For larger-sized foods, their gastric breakdown rate and gastric acidification rate were slower, which extended their contact time with salivary amylase in the proximal stomach. To elucidate further the role of the proximal and distal phases of gastric digestion in solid food breakdown, a static in vitro digestion was conducted with the same food products. In the smaller-sized foods, both the proximal and distal phases led to their dissolution. Meanwhile, for the larger-sized foods, the extended contact time with α-amylase in the proximal phase contributed to the leaching of starch particles from the food, which was important to aid their breakdown during gastric digestion. The distal phase contributed to the softening of the larger-sized foods, but its softening effect was limited. The knowledge on the contributions of the phases of gastric digestion and the identified link between food structure, gastric digestion, and glycemic response in this thesis may be useful for structuring starch-based foods with controlled glycemic properties.