Effect of substituting baking water with brewer's spent grain supernatant on the micro-structure and crumb structure of white wheat flour bread

Van Zyl, Nicola Jean (2019-04)

Thesis (MScFoodSc)--Stellenbosch University, 2019.

Thesis

ENGLISH ABSTRACT: The ubiquitous opinion regarding brewer’s spent grain (BSG), is that it is currently underutilised, based on its residual nutritional contents and potential for re-use. This is a process by-product that is available throughout the year, in most countries, at a very low cost from micro- to industrial-sized breweries. For this research assignment, freshly produced BSG was processed using a screw-press which enabled the extraction of BSG-supernatant, a liquid consisting of 98% water. Using the supernatant would require less energy-intensive processing, compared to preparing a composite-flour from the spent grain through drying and milling of BSG. Very little research has been undertaken with the objective of determining the effect on bread quality parameters when using an alternative baking water. The functional role of baking water in producing a quality bread product was reviewed. The knowledge gained therefrom enabled the evaluation of the potential of BSG-supernatant as an alternative baking water in white bread formulations. The experimental design and research objectives of this investigation were employed in order to review the proposed removal of the excess moisture within fresh BSG. The liquid fraction is separated from its solid, fibrous origin and clarified through the gravimetric sedimentation of suspended fibrous-particulates. The BSG-supernatant’s effect on the dough’s rheological behaviour and quality scores were evaluated according to bread industry standards and regulations. Macro- and micro-structural properties of the bread samples were evaluated using Texture Analysis (TA), C-Cell Visual Analysis (2D) and X-ray micro-Computed Tomography (3D) across a shelf-life period (Days 2, 3 and 4). The micro-structural properties of bread loaves were evaluated in terms of their cell properties within the crumb-structure, as well as its porosity and water holding capacity (WHC). BSGsupernatant was determined to have no significant effect on the micro-structural properties of the bread loaf, although the crumb-structure of the BSG-supernatant breads had a greater WHC than did that of the control formulations. The control- and treatment formulations were compared on a 5% significance level and it was concluded that BSG-supernatant can be used as an alternative baking water, for white bread formulations, without being detrimental to loaf quality.

AFRIKAANSE OPSOMMING: Die alomteenwoordige opinie aangaande BSG, is dat dit tans onderbenut word, gebasseer op die oorblywende voedingsinhoud, en BSG se potensiaal vir hergebruik. Dit is tans 'n afvalproduk wat dwarsdeur die jaar beskikbaar is in meeste nasies, vanaf mikro- en industriële brouerye teen 'n baie lae tarief. Vir hierdie ondersoek is vars geproduseerde BSG verwerk met behulp van 'n skroefpers wat die ekstraksie van BSG-supernatant, 'n vloeistof wat uit 98% water bestaan, moontlik gemaak het. Die gebruik van die supernatant benodig minder energie-intensiewe prosessering, in vergelyking met die voorbereiding van BSG-meel deur die dehidrasie en maal van vars BSG. Baie min navorsing is beskikbaar, met betrekking tot die effek op broodkwaliteits eienskappe wanneer ‘n alternatiewe bakwater gebruik word om brood to produseer. 'n Omvattende literatuuroorsig is saamgestel om vas te stel wat die funksionele eienskappe is wat water bied in ‘n brood formulasie en produksie prosedures. Die funksionele rol van bakwater in die vervaardiging van 'n goeie gehalte broodproduk is as gevolg hersien. Die kennis wat in die proses versamel is, het die evaluering van die potensiaal van BSG-supernatant as 'n alternatiewe bakwater gerealiseer. Die eksperimentele ontwerp en navorsingsdoelwitte van hierdie ondersoek is in diens geneem om die ekstraksie van die oortollige vog (water) binne vars BSG te oorweeg as ‘n alternatiewe bakwater. Die BSG-supernatant is geskei van die gesuspendeerde veselagtige materiaal, deur die vloeistof te laat staan. Die BSG-supernatant se effek op die broodmeel se rheologiese eienskappe en brood kwaliteit is geëvalueer volgens broodbedryf-standaarde en regulasies. Makro- en mikrostruktuur eienskappe van broodmonsters, van beide ‘n oorspronklike en BSGsupernatant brood formulasies, is geëvalueer met behulp van Tekstuur-analise (TA), C-Cell Visuele Analise (2D) en X-ray micro-Computed Tomography (X-ray μCT) tydens 'n brood se rakleeftydperk (Dae 2, 3 en 4 na- produksie). Die mikrostrukturele eienskappe en veranderinge tydens ‘n vasgestelde rakleeftyd, was evalueer deur die sel-struktuur binne-in die brood se krummel-struktuur te vergelyk met die van die kontrole s’n. Die mikrostruktuur van die brode was ook evelueer deur te kyk na die porositeit van die brood se spons-struuktuur. Dit was bepaal dat die BSG-supernatant geen negatiewe invloed op die mikrostruktuur van ‘n witbrood het nie. Daar is tog ‘n merkwaardige gevolgtrekking gemaak, dat die WHC van die BSGsupernatant brode ‘n verbeterde krummel-struktuur WHC gehad het. Die BSG-supernatant en oorspronklike wit-brood formulasie was vergelyk op ‘n 5% betekenisvlak, waartydens die gevolgtrekking gemaak is dat die BSG-supernatant as ‘n effektiewe, alternatiewe bakwater benut kan word in wit-brood formulasies, sonder om die kwaliteit van die finale brood produk te benadeel.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/106026
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