Effect of Quality of Wheat and Maize Flour in Tempura Batter

Abstract

Tempura batters are stand-alone systems that are not further breaded. They provide a protective coating which can range in texture from crispy/crunchy to cake-like. Recipes for batter systems are adjusted empirically, and the choice of ingredients, especially flour, will determine the quality and acceptability of coating. This study aims to characterise wheat and maize flours that would optimise fried tempura quality, and to study their effect on behaviour of batters, and quality of fried products. In aqueous ethanol, results showed RVA to be useful to characterise wheat flours for batter applications. There is a close relationship between flour attributes and flour starch pasting behaviour. Positive correlation was found between 1st peak viscosity (starch) and 2nd peak viscosity (protein) (r = 0.768). Farinograph and Extensograph data were correlated to RVA, but of minimum use for flour batter functionality due to the absence of a gluten network. Maize plays a strong role in batter viscosity control, and various viscosity measuring methods were applied. Empirical methods were easy and rapid, but arbitrary, subjective and not precise. Imitative tests were an improvement, but less precise than rheometry. The BS cup method was more accurate at 50ml than at 70ml, and they were positively correlated (r2 = 0.99). Back extrusion (BE) data showed a strong correlation with CFS and BS cups measurement. Using Pearson correlation analyses, positive correlations were found between viscosity from BS Cup and firmness (r = 0.851), BS cup and consistency (r = 0.891), CFS cup and firmness (r = 0.74), and CFS cup and consistency (r = 0.768). Therefore, BE is recommended as an alternative to the above. Maize flour pasting properties varied with the flour particle size. Peak viscosity correlates negatively with particle size (r = -0.959), and positively with starch damage (r = 0.83). Rheology of different flour combinations in tempura batter was studied, and links between texture parameters in relation of flour type and concentration were established, and can be used to guide development/selection of wheat and maize flour for batters. An electron microscopy low vacuum low temperature SEM method was used successfully to visualise the microstructure of a range of deep-fried battered chicken samples linked to specific formulations which established links between structure and function, and eating qualities.

Sensory evaluation of texture discriminated between coatings on chicken pieces, and was consistent to instrumental analysis, i.e. extended Kraft knife on crust and core while simultaneously measuring the sound pressure level of the emitted sound. Acoustic parameters extracted from the compression curves were useful. Positive correlations were found between breading crispness with No. force peaks and No. sound peaks, i.e. r = 0.749 and r = 0.693 respectively. Moisture and fat contents of the core and crust were related to the texture, but exceptions were linked to very dissimilar crispness; which would depend on water distribution within the crust. Ease of breakdown on the mouth contributes to preferences of texture. More work on the interaction between wheat and maize flours, and batter rheological, thermal, and textural properties, will further this project’s significant contribution to the knowledge of the effects of flours selection and formulation on batter technology and coated product quality.