The effects of moisture sorption on physical properties of native and cross-linked starch films in the glassy state were studied. Water played a dual role as a plasticizer or an antiplasticizer, depending on the physical property measured. Plasticizing effects were clearly evident in the case of the calorimetric glass transition temperature (T g ), tensile modulus, linear expansion, and water vapor permeability. In contrast, antiplasticization by water resulted in maxima in tensile strength, strain-at-break, and toughness of films that were observed at an intermediate moisture content ranging from 4% to 8% (RVP 0.1 to 0.4). The seemingly contradictory effects of water on mechanical properties associated with lower and higher deformation of starch films were reconciled by assigning different roles to water operating primarily via opposite entropic/free volume effects. Relationships, if any, between DSC thermal events and mechanical antiplasticization were not apparent.

No abstract

Coconut milk, a generic term for the aqueous extract of the solid coconut endosperm, plays an important role in the cuisines of South East Asia as well as other parts of the world. This broad-spectrum review collates widely scattered information on the extraction, chemical properties (with special emphasis on the protein components), keeping quality, processing and preservation (particularly by canning, spray-drying and freezing) and new food uses of coconut milk.

Antiplasticization of synthetic glassy polymers by lowmolecular weight diluents at low concentrations is a wellknown phenomenon which leads to increased rigidity rather than flexibility of the polymer-diluent blends. Based on the food polymer science approach, we hypothesized that increases (rather than decreases) in modulus and brittleness, commonly observed when certain solid food systems are humidified from the dry state, are synonymous with antiplasticization by water. Sugars and polyols, important components of foods, behave in much the same manner as water in acting as either antiplasticizers or plasticizers of food polymer systems. Several mechanisms may be involved in antiplasticization by low-molecular mass diluents. Simultaneous changes in various physical properties, resulting from antiplasticization or plasticization by water and other diluents, may profoundly influence the quality and acceptability of food products.

Using a Rapid Visco Analyzer (RVA), it was revealed that 2 alkalizing agents (Na 2 CO 3 and NaOH) had a far larger effect on pasting properties of nonwaxy starches (wheat, corn, rice) compared with their effect on waxy starches (waxy corn and waxy rice). It was hypothesized that the alkalizing agents have a greater propensity to attack the amorphous regions of the nonwaxy starch granules, thereby causing increased leaching of amylose molecules and possibly also some hydrolysis of starch chains. As a result, the RVA pasting profile of a nonwaxy starch, in the presence of alkali, was drastically altered to one that more closely resembled that of its waxy counterpart without added alkali.