The effect of temperature on gluten conditioned at the following water contents, 0%, 13%, and 47% (wet weight basis), was studied by FTIR spectroscopy over the temperature range of 25-85 degrees C. A detailed discussion of the assignment of the amide I band is given. At 0% hydration no changes in the secondary structure with temperature could be detected; spectra were consistent with a tight disordered structure with many protein-protein interactions. At 13% hydration, distinctive changes occurred in the low-frequency region of the amide I band (1,630-1,613 cm(-1)). This was attributed to changes in the beta-sheet structure. On cooling to 25 degrees C, these changes were mainly reversed. It was noted that most of the changes observed occurred above the glass transition temperature. At 47% hydration, more complex changes took place: as the temperature was raised distinct bands at 1,630 and 1,613 cm(-1) merged. However, this process was partially reversed, with recovery of both bands, on cooling. The significance of these results in relation to other changes in gluten proteins in flour and dough with temperature and water content is discussed.

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Zein, the main seed storage protein of maize, has been widely studied as a possible source of material for the production of biodegradable plastic films. Plasticization of zein is critical to make functional films. While there have been a number of publications which report the behavior of systems with a wide variety of plasticizers, there have been few which attempt to examine the interactions of protein and plasticizer at the molecular level. In this paper, we report on the plasticizing effects of water, glycerol, and 2-mercaptoethanol, which were examined by a combination of spectroscopy (FTIR and dielectric) and thermomechanical methods. The results suggest that both water and glycerol are adsorbed onto the protein and form hydrogen bonds with the amide groups. The plasticizer then builds up in patches on the protein surface. 2-Mercaptoethanol only exhibited a weak plasticizing effect due probably to disulfide bond breaking.

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A method developed for in situ imaging of starch granule structure in dry seeds has been applied to compare the starch granule structures found in wild type and ae mutant maize kernels. In the isogenic ae mutant the activity of the starch branching enzyme IIb is inhibited, which gives rise to a high amylose starch. The granule structures in the wild type samples have been found to be homogeneous, whereas those in the ae mutant are grossly heterogeneous within individual granules, between granules within individual cells, and between cells across the endosperm. The level of heterogeneity observed in situ appears to be more marked than that previously reported for studies on isolated ae mutant starches. Iodine/potassium iodide staining and polarised light microscopy have been used together with Raman microscopy, which has allowed high‐resolution mapping of the composition and physical state of the structures within the granules, to probe the origins of the heterogeneity of the starch structures. Although the mutation inhibits the activity of the branching enzyme within the granules, and both the composition and level of crystallinity within and between granules is variable, the major origin of the heterogeneity of the granule architecture appears to result from significant changes in the assembly and packaging of the crystalline structures within the granule. It is suggested that this arises due to the mutation of the starch branching enzyme introducing defects into the self‐assembly of the crystalline structure, resulting in an accumulation of defects and increased randomisation of the granule structure.

In the present study the effect of iodine on properties of zein films and zein precipitates obtained after hydrophobic aggregation was evaluated. Zein films were cast with and without glycerol (as plasticizer) after incorporation of iodine at different levels (2-8%, zein wt basis). Zein films were characterized by secondary structure (determined by infrared spectroscopy) and dielectric and mechanical properties. The rheological properties of zein precipitates as a function of frequency and temperature were evaluated using a dynamic rheometer. Inclusion of iodine changed the secondary structure of zein films and decreased their tensile strength as well as strain at failure. In aggregates, changes in G' (elastic modulus) and G'' (viscous modulus) during heating were affected by the presence of iodine due to the inhibition of aggregation. The water-holding capacity of precipitates precipitated in the presence of iodine was higher than that of those without iodine.

The effect of calcium chloride (CaCl2)(5 gL-1) and sodium chloride (NaCl) concentration (40, 60 and 8 gL-1) on the microbiological and mechanical properties of naturally black olives of cv. Conservolea in brines was studied. In 40 and 60 g L-1 brines the growth of lactic acid bacteria was favoured over that of yeasts, resulting in rather complete lactic acid fermentation as indicated by high free acidity (9.8–11.5 g lactic acid L-1) and low pH (3.7–3.8). At 80 g L-1 brine, yeasts were the dominant members of the microflora, rendering a product with lower acidity (8 g lactic acid L-1) and higher pH (4.3–4.5). In the presence of CaCl2 there was a consistent increase in the depth of the peripheral region in which cell wall breakage occurred. When cells separated, perforated walls were observed at sites associated with plasmodesmata. The flesh was strongest and stiffest when CaCl2 was added to olives treated with 40 g L-1 brine, consistent with cell wall breakage being the predominant mode of failure. The only observed effect on the mechanical properties of the skin was a stiffening at 60 g L-1 brine on addition of CaCl2