Effect of oven and forced convection continuous tumble (FCCT) roasting on the microstructure and dry milling properties of white maize. (December 2017)

• Record Type: Journal Article
• Authors: Schoeman, Letitia; du Plessis, Anton; Verboven, Pieter; Nicolaï, Bart M.; Cantre, Dennis; Manley, Marena
• Is Part Of: Innovative food science & emerging technologies. Volume 44(2017)
• Page Start: 54
• Page End: 66
• Publication Date: 2017-12
• Subjects: Maize kernels -- X-ray micro-computed tomography -- Image analysis -- Milling yield -- Kernel hardness -- Material density; Food -- Biotechnology -- Periodicals; Food industry and trade -- Technological innovations -- Periodicals; Aliments -- Biotechnologie -- Périodiques; Food -- Biotechnology; Periodicals; Electronic journals; 664.005
• DOI: 10.1016/j.ifset.2017.07.021
• Languages: English
• ISSNs: 1466-8564

Abstract

Abstract: The effect of oven and forced convection continuous tumble (FCCT) roasting on the microstructure of whole maize kernels was characterised and quantified using X-ray micro-computed tomography (μCT). The three-dimensional (3-D) volumes, reconstructed from the two-dimensional (2-D) images, were segmented into regions of interests (ROIs), i.e. air, germ, floury and vitreous endosperm, and each region quantified. Oven roasting was associated with a larger increase in total kernel volume (10.8%) than FCCT roasting (3.4%) as well as a significant (P ≤ 0.05) decrease in whole kernel relative density (oven = 6.3%; FCCT = 1.9%). FCCT roasting had almost no effect on material density, in contrast to a significant (P ≤ 0.05) decrease of 5.0% during oven roasting. Subsequent validation of the dry milling properties, i.e. percentage hominy chop, milling yield and hectolitre mass (HLM), indicated no significantly (P > 0.05) detrimental effect by either of the roasting methods. Industrial relevance: Roasting of maize can improve sensory, shelf life, nutritional and antioxidant properties with subsequent use in ready-to-eat foods and breakfast cereals. Roasting will inevitably affect the structure of maize, which in turn will affect the quality of the end product. This prompted the demand for non-destructive techniques that directly measure microstructural properties of food in order to link structure with quality. X-ray μCT in combination with image analysis uniquely illustrated the microstructural changes occurring during conventional oven and innovative FCCT roasting respectively. Furthermore, dry milling properties are important indicators of quality characteristics for the dry milling industry. The method described in this article can be applied to any food material to investigate structural properties. Highlights: Forced convection continuous tumble roasting is less destructive than oven roasting. Milling properties remained unaffected during both roasting methods. Roasted maize can be characterised using X-ray micro-computed tomography (μCT). X-ray μCT allows quantitative evaluation of different regions-of-interests (ROIs).