New possibilities in micro-scale wheat quality characterization: Micro-gluten determination and starch isolation

摘要

When sample size is limited, small-scale dough testing methods are needed. Since the development of the 2 g Mixograph, the first commercially available small-scale dough testing instrument, followed by the appearance of micro-extension instruments andmicro-dough inflation procedures, intense research activities have been carried out to evaluate different micro-scale systems as well as studying the effects of reduced sample quantities on the measured parameters. During the last decade, a family of micro-scale instruments have been developed through long-term cooperation between Hungarian and Australian partners; resulting in prototypes of a micro-mill and a micro-sieve, a Farinograph/ Valorigraph-type micro-Z-arm mixer, and a combined macro- and micro-sedimentation tester (Sedicom~R) followed by commercialization of these instruments. Recently, a new type of gluten and starch washer (GluStar~R, BME-Labintern, Hungary) was constructed. The novelty of this system is its capability of determing wet gluten content and isolating eluted starch and soluble components of flour from one cycle. Both macro- and micro-modes of application are possible, with sample requirements of 10 g or 4 g of flour, respectively. The modularity of the measuring system ensures the separate utilization of the basic modules (gluten washer, and carbohydrate collector). The gluten washer alone is applicable for measuring wet gluten content. The method was validated, and results were found to be well correlated with generally used standard methods. The equipment has been used in various research studies, such as screening large sample populations of Hungarian and Australian wheat lines, with satisfactory reproducibility in wet gluten content and providing starch samples for further chemical and functional tests. Some examples for the application of the new equipment are given, including an investigation of the impact of the AM/AP ratio and the arabinoxylan (AX) content on rheological properties of samples for producing blendsof conventional bread wheat flours with high-amylose and waxy wheat flours.