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Does a Vegetable-enriched Nothing Else™ Bread Have Benefits to Health?

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Date

2020

Authors

Supervisor

Rush, Elaine Carolyn
Cairncross, Carolyn

Item type

Thesis

Degree name

Doctor of Philosophy

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Publisher

Auckland University of Technology

Abstract

Bread is one of the most consumed foods, world-wide and in New Zealand. Currently, the paradigm of new bread and functional food development offers the opportunity for incorporation into wheat flour plant-based ingredients such as vegetables, seeds and whole grains to allow for the making of health claim on a food product. In addition, there is a call for food to be less processed and to contain sustainable ingredients, and for food labels to be simplified and clean. The Auckland University of Technology (AUT) Nothing Else™ front-of-pack brand can only be used on products with eight or fewer wholesome ingredients and would be appropriate for a healthier bread. The overarching research question that drove this research was “How can food science and nutrition inform the development of a vegetable-enriched Nothing Else™ bread, accepted by consumers, with potentially verifiable health claims?” Six chapters describe the body-of-work undertaken to answer this question. The first part of the review of literature (Chapter 2) focuses on the effect of the enrichment of bread with functional ingredients on its physical and sensory attributes, including the swallowing of bread. Swallowing was investigated because as a population ages the prevalence of chewing and swallowing difficulties increases. In addition, many older people have discretionary funds which potentially increase their ability to buy palatable and nourishing bread which is easy to swallow. In collaboration with an advisory support group, two breads (VB75 and VB100) were formulated and produced in-house at the AUT School of Hospitality kitchens with eight ingredients including drum-dried pumpkin and sweet corn flours, flaxseed, and sprouted wheat and wholemeal wheat flours (Chapter 3). The first experimental study (Chapter 4) evaluated the physical, subjective ease of chewing and swallowing and sensory attributes for four breads of increasing healthiness: commercial white (WB) and wheatmeal (WMB) $1 breads, and the two in-house breads enriched with mixes of pumpkin and sweet corn flours (VB75 and VB100). Objective texture measures (TA.XT.plus texture analyser, Stable Microsystems, Surrey, UK) were assessed for four 11.5 mm thick bread crumb slices of the WB, WMB, VB75 and VB100 breads. Fifty physically active volunteers aged 50+ years rated on Likert scales liking and ease of bite and getting the bread into the mouth, ease of chewing and swallowing, and ease of bread bolus movement through the throat. Number of chews before swallowing were also recorded. The VB75 and VB100 were liked almost twice as much as the WB and WMB in all the sensory attributes assessed. Overall liking of all breads was correlated with ease of swallowing: VB75 r=0.597, 95% CI (0.382, 0.751); VB100 r=0.665, 95% CI (0.474, 0.796); WB r=0.422, 95% CI (0.163, 0.627); and WMB r=0.475, 95% CI (0.227, 0.665). Objectively, the breads were not different in hardness but differed in measures of chewiness, resilience, cohesion, springiness and gumminess. Subjectively and objectively, WB and WMB recorded the highest chewiness values (50% higher than VB75 and VB100). The vegetable-enriched breads required less chewing and were rated twice as easy to chew by the participants. After swallowing, the vegetable-enriched breads were perceived by the participants to move almost twice as easily through the throat compared to the commercial breads. The second literature review (Chapter 5) was a systematic search for published literature in the databases PubMed, Web of Science and Cochrane Library via Wiley and OVID on reports of the validation of “health claims” or “health effects” of bread enrichment with “functional ingredients”. The main published finding was that functional bread has the potential to attenuate glycaemic response and reduce appetite which may reduce risk for diet-related non-communicable diseases. In the second experimental study (Chapter 6), the VB75 (VB) from the first study (Chapter 4) was selected and investigated for its glycaemic and appetite suppression potential when compared with commercial WMB and WB over a 120-minute period. After an overnight fast, 10 apparently healthy, young participants (23±7 years, 70% Pacific) received in random order on three separate days, 75g of the three breads WB, WMB and VB. Blood was sampled before and 15, 30, 45, 60, 90 and 120 minutes after the bread consumption. The incremental-area-under-the-curve (iAUC) for glucose and insulin was determined and an appetite questionnaire completed by participants at each timepoint. The mean glucose iAUC were not different among breads. However, the mean insulin iAUC for the VB was significantly less than for the WB and WMB; VB and WB 12415pmol/L*minutes (95% CI 1918, 22912pmol/L*minutes, p=0.025) and VB and WMB 13800pmol/L*minutes (95% CI 1623, 25976 p=0.031). Over the 120-minute period following consumption, compared to the WB and WMB, VB stimulated a stronger fullness feeling in the participants. The VB (β-carotene 236.78µg/100g and fibre= 7.2/100g) could be an effective carrier for the delivery of carotenoids and fibre if consumed every day. The third and final experimental pilot study (Chapter 7) primarily sought to investigate whether this vegetable-enriched bread, when consumed every day (200g/day) over two weeks, would increase plasma carotenoid concentration and improve lipid profile. A secondary analysis was carried out for criterion validation of the Veggie meter™ reflection spectroscopy measures of skin carotenoid scores against laboratory-based plasma carotenoid concentration, and for construct validation against a six-item carotenoid food frequency questionnaire. The daily consumption of 200g of VB over two weeks showed no measurable change in the plasma carotenoids or lipid concentrations. There was a strong correlation (r=0.845 and 95% CI 0.697, 0.924) between the plasma carotenoid concentration and the Veggie meter™ scores (n=30). A positive correlation was observed for participants (n=10) average baseline and post-intervention vegetable intake and their plasma carotenoid measure (r=0.446, 95% CI -0.255, 0.840 and r=0.255, 95% CI -0.446, 0.762 respectively) and skin carotenoid reflection score (ρ=0.489 and Ϯ=0.689). Reported compliance with consumption of the bread was 100%. In conclusion, this proof-of-principle work (Chapter 8) has demonstrated that, when compared to WB and WMB, vegetable-enriched breads have the potential to improve nutrition status and ‘ease of swallowing’ especially in older people and those who are susceptible to dysphagia. The consumption of VB was associated with a lower insulin release and higher satiety which may be related to the higher fibre and less-chewy texture of the VB. Finally, the consumption of 200g VB for two weeks caused no substantial changes in plasma carotenoid and lipid concentrations. Future works should focus on the long term consumption of the VB and its association with any changes in glucose tolerance, weight, lipid profile and gut microbiome. Additionally, the need to investigate the economics and commercial viability of bread production using novel functional ingredients such as dried vegetables and clean-label branding such as the Nothing Else™ brand is encouraged.

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Keywords

Vegetable-enriched bread, White bread, Wheatmeal bread, Physical quality, Liking, Swallowing, Glycaemic response, Appetite suppression, Carotenoids, Lipid profile, Veggie meter™

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Permanent link

https://hdl.handle.net/10292/13587

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Doctoral Theses