Cereal Chem. 82(5):609-615The formulation of gluten-free (GF) bread of high quality presents a formidable challenge as it is the gluten fraction of flour that is responsible for an extensible dough with good gas-holding properties and baked bread with good crumb structure. As the use of wheat starch in GF formulations remains a controversial issue, naturally GF ingredients were utilized in this study. Response surface methodology was used to optimize a GF bread formulation primarily based on rice flour, potato starch, and skim milk powder. Hydroxypropylmethylcellulose (HPMC) and water were the predictor variables. Analyses of the treatments from the design were made 24 hr after baking. Specific volume and loaf height increased as water addition increased (P < 0.01). Crumb firmness decreased as water levels increased (P < 0.01). Significant interactions (P < 0.01) between HPMC and water were found for the number of cells/cm 2 . The number of large cells (>4 mm 2 ) decreased with increasing levels of HPMC and water. Optimal ingredient levels were determined from the data obtained. The optimized formulation contained 2.2% HPMC and 79% water flour/starch base (fsb) and measured responses compared favorably to predicted values. Shelf-life analysis of the optimized formulation over seven days revealed that, as crumb firmness increased, crust firmness and crumb moisture decreased. 2 Corresponding

Studies were conducted to develop gluten-free biscuits comparable in quality to wheat (W) biscuits and superior to those made from commercial gluten-free flour (Gf), suitable for coeliac sufferers. Three mixes of brown rice flour (R), corn starch (C), potato starch (P), soya flour (S), buckwheat flour (B) and millet flakes (M) were studied: RCPS in the percentage 70, 10, 10, 10, RPBM (50, 30, 10, 10) and RCPM (25, 25, 25, 25). Biscuits were tested for water activity, moisture, texture (snap test), diameter, thickness and colour (L* value), biscuit dough for hardness and stickiness. Various correlations >0.8 indicated for the three mixes, W and Gf that firm, nonsticky doughs yielded firm, thin, non-oval biscuits. Cluster analysis revealed that RCPS was most similar to W with regards to all parameters measured, and RCPS also showed best overall acceptability in sensory testing. Three fat powders were studied for use instead of palm oil: high and low fat dairy powder (HFP, LFP) and microencapsulated high fat powder based on vegetable fat (ME). HFP and ME yielded biscuits of comparable texture to palm oil, LFP resulted in much firmer biscuits, attributed to lower fat and higher protein and total sugar content.

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Starch digestion is of great importance to human health with a large fraction being digested in the small intestine. However, starch material that escapes digestion by amylolytic enzymes in the upper gastrointestinal tract is termed 'resistant starch' (RS). RS has been subdivided into four groups; physically inaccessible starch (RS1), native (uncooked) starch (RS2), retrograded (cooked and cooled) starch (RS3), and chemically modified starch (RS4). The amount of RS can vary considerably depending upon the botanical source and the food processing conditions applied. Many groups have reported that starches of high amylose content that have undergone temperature-cycled retrogradation contain increased amounts of retrograded starch (RS3) 1 . The purpose of this project is to harvest, characterise and perform enzyme inhibition studies on isolated RS from high amylose maize starch (HA).In our study, retrogradation of HA at cycles of 4/37°C for 1 week significantly increased the RS content to 95%. This allows accurate enzyme inhibition studies to be performed. X-ray diffraction (XRD), scanning electron microscopy (SEM) and nuclear magnetic resonance ( 13 C NMR) was then used to determine the structure of RS. Surprisingly, upon XRD and NMR analysis, our results suggested that the isolated RS possessed low crystallinity. SEM images showed a web -like pattern connecting the starch material together. This resulted in associated 'lumps' of starch material rather than a continuous polymer network which is commonly seen in gelatinised starches. Thus the majority of the starch material is believed to be amorphous; however this amorphous material is clearly of a different form compared with the SEM images of amorphous gelatinised starches 2 . Upon digestion with pancreatic α-amylase, no starch products were detected indicating RS is totally inert to digestion (n = 4). In addition to this, inhibition studies suggest RS acts as a non-competitive inhibitor of pancreatic α-amylase.To conclude, ready to eat chilled foods which have undergone retrogradation may have reduced starch digestibility. Therefore, the physiological effects of RS on human metabolism may have beneficial relevance in the management of health and disease (e.g. obesity and type II diabetes).