Effect of adding wheat (Triticum aestivum L.) farina with varied integrity of endosperm cell wall on dough characteristics, dried noodles quality and starch digestibility.

The changes of intact endosperm cell wall in cereal food processing and its effect on starch digestibility are important for developing nutritious and healthy next generation foods, but their changes in the process of traditional Chinese cooking products such as noodles making have not been investigated. In this paper, the changes in endosperm cell wall in the process of making dried noodles by adding 60 % wheat farina with varied particle sizes were tracked, and the underlying mechanisms affecting the noodle quality and starch digestibility were revealed. With increasing particle size (150-800 µm) of farina, the contents of starch and protein, swelling index of glutenin, and sedimentation value decreased significantly and the dietary fiber increased sharply; moreover, water absorption, stability and extensibility of dough decline obviously while the resistance to extension and thermal stability were enhanced. In addition, noodles made with flour added larger-particle size farina had a lower hardness, springiness, and stretchability while a higher adhesiveness. Compared to the flour and other samples, the flour with the smaller-particle size farina (150-355 µm) showed better rheological properties of dough and cooking quality of noodles. Furthermore, the integrity of the endosperm cell wall increased with increasing particle size (150-800 µm), which was perfectly preserved during noodle processing and was an effective physical barrier to inhibit starch digestion. The starch digestibility of noodles made from mixed farina with low protein content (∼15 %) did not significantly reduce compared to that of wheat flour noodles with high protein content (∼18 %), probably due to the increased cell wall permeability of noodle processing, or the overwhelming effect of noodle structure or protein content. In conclusion, our findings will contribute to an innovative perspective for in-depth understanding of the impact of endosperm cell wall on the quality and nutrition of noodles at the cellular level, which provided a theoretical basis for the moderate processing of wheat flour and the development of healthier wheat-based food products.

Effect of roasting process on enzymes inactivation and starch properties of highland barley.

Roasting may be beneficial to extend the shelf life by inactivating the lipases and peroxidases in highland barley, but it may lead to the deterioration of starch quality. In this study, the pre-treatment techniques of pearling and tempering were tried to improve the efficiency of inactivation, and different roasting treatment parameters were compared to obtain the optimum treatment conditions, under which thermally degraded starch may be less. Pearling had been proved to be an effective means in reducing enzyme content, and tempering could improve the sensitivity of enzymes to heat. Synergism of the two pre-treatment methods increased the inactivation of lipase and peroxidase in highland barley to 80% and 100%, respectively, and the optimal pre-treatment and roasting condition was P20M16T16 (20% pearling rate, 16% moisture, and 16 min treatment time) at 180 °C. Under this condition, the starch quality was basically consistent with those of control starch. For roasting treatment starch, the birefringence intensity, swelling power, and solubility slightly decreased and the polarized cross also still existed, while the relative crystallinity slightly increased and the crystal type unchanged. Roasting treatment starch showed higher pasting temperature and lower paste viscosity, and the increasing To, Tp, and the decreasing enthalpy.

Comparative studies on physicochemical properties of total, A- and B-type starch from soft and hard wheat varieties.

Starch from soft wheat and hard wheat varieties was evaluated for physicochemical properties, including pasting and retrogradation properties, swelling power and solubility, and granule morphology. Grain hardness index of soft and hard wheat varieties ranged from to 25 to 35, and 71 to 82, respectively. Soft wheat varieties showed a larger proportion of total starch (TS) and A-type starch (AS), and a smaller proportion of B-type starch (BS). The amylose content of starch from hard wheat varieties was significantly higher than that from soft wheat varieties. Starch from soft wheat varieties exhibited higher pasting viscosity, transmittance, swelling power, and smaller crystallinity as compared to starch from hard wheat varieties. BS from hard wheat exhibited the lowest average breakdown and setback viscosity, hardness, adhesiveness, and fracturability. AS exhibited the highest pasting viscosity, better transparency, gel properties, freeze-thaw stability, swelling power, clearer "Maltese cross", and higher crystallinity, whereas BS exhibited the highest gelatinization temperature, better gel stability and solubility. The study might broaden the recognition of starch from different wheat varieties, and provide a theoretical basis for wheat breeding and the potential utilization of different types of wheat starch and flour.