Effects of seasonal and short-term changes during storage on the breadmaking performance of home-grown wheat.
Salmon, S. E.;
HGCA Project Report Year: 1998 Issue: No. 160 Pages: 109 pp. Ref: 65 ref.
1998
บทคัดย่อ
In trials over various harvests in the UK, breadmaking wheat cultivars (Avalon, Fresco, Hereward, Mercia and Torfrida) representing different protein quality classes, were milled as soon as possible after harvest before being stored at -18 deg C (control flour) or under controlled conditions of 15-20 deg and approx. 50% RH (stored flour). The remaining wheat was held under an equivalent storage regime to the stored flour and at predetermined time-points samples were removed for comparison of milling and breadmaking quality potential. This protocol was devised to permit separation of the effects of wheat storage after harvest and normal flour storage over the same period (approx. 8 months) on end-use quality. Optimum milling performance in a laboratory Buhler mill was generally not achieved until wheat had been subjected to a period of storage prior to milling. In particular, the endosperm appeared to be easier to separate from the bran and a slight increase in flour particle size was observed af
ter storage. Sieving problems have been perceived by millers when using new crop wheat and increased granularity would be expected to improve flour flow characteristics, but the Instron method used to test ease of flour movement and potential for bridging proved too imprecise to enable a firm conclusion to be made on this point. Effects on milling performance were generally overcome by storage for approx. 6 weeks, confirming the value of blending old and new crop wheat at harvest changeover. Storage, as wheat or flour, had no significant effect on basic chemical and rheological properties of white flour. Any observed changes in flour quality characteristics could be related to milling differences, i.e. increases in flour extraction. Wheat storage prior to milling had no consistent, significant effect on final quality in a standard Chorleywood Breadmaking Process (CBP). Prolonged flour storage (for up to 8 months) generally resulted in a deterioration in quality as indicated by reduced CBP loaf volume. This d
ecline in quality was associated with increased free fatty acid levels and reduced sulphydryl content of flour. There was no evidence of cultivar susceptibility to postharvest changes, but seasonal variations had a major impact on quality for breadmaking. The magnitude of season-to-season differences generally exceeded any wheat storage effect and no solution to this natural, annual variation in protein content and protein quality could be recommended from biochemical studies.