The physical properties of corn, wheat and rice starch edible films with different level of glycerol were evaluated. Starch films exhibited an apparent endothermic peak in the range of 151–199°C with corn starch film with 1.6% glycerol having a relatively lower T_o and higher T_p. X-ray diffraction spectroscopy indicated that the corn, wheat, rice starch powders had ~ 39–49% crystallinity, whereas Fourier transform infrared spectra showed peaks associated with the tightly bound water present in the rice, corn, wheat starches. Overall, glycerol addition could enhance the water vapour pressure barrier properties of the films, but their tensile strength was reduced. Corn starch films were identified as the most suitable choice for edible packaging as its thermal characteristics indicated suggested a more acceptable sealability. Rice starch films is proposed as the better choice for coating as it showed better flexibility as indicted by lower tensile and higher elongation properties.

Gum karaya is a polysaccharide gum from Sterculia urens tree. It is used as an emulsifier and thickening agent in cosmetics and pharmaceuticals. However, it has very strong swelling properties, high viscosity, and low solubility, providing the restricted applications in the food industry. The main objective of this study was to investigate the effects of different heat treatment and microwave variables (i.e., time: 8, 10, and 12 min; power: 700 and 1000 W) on the functional properties of gum karaya in the aqueous system and oil-in-water emulsion. In this regard, the rheological properties, emulsifying activity, average droplet size, and surface morphology of the native-and microwave-treated gums were analyzed and compared. Dynamic oscillatory test indicated that the microwave-treated gum karaya had more gel-like behavior than viscous-like behavior (G′ > G″) at a relatively high concentration (20% or 20 g/100 g). When gum karaya was treated by microwave for 8-12 min, both elastic (G′) and viscous (G″) moduli were declined. The native-and microwavetreated gum karaya exhibited a shear-thinning (pseudoplastic) behavior in the aqueous system and oil-in-water emulsion. The results showed that the microwave-treated gum karaya had smaller particles than the native gum in the aqueous system. On the other hand, the emulsion containing the microwave-treated gum karaya had finer emulsion droplets than the control containing the native gum karaya. This confirmed that the application of microwave treatment led to significantly (p < 0.05) improve the emulsifying activity of gum karaya.

Effects of different rice starch‐based coating formulations on physical properties of walnut were studied during 20 days storage at accelerated temperature. Results from different starch films indicated there were nonsignificant differences in water and oxygen barrier properties of the starch films. However, significant (p ≤ .05) differences were present in the elongation at break characteristics between the corn and rice films. Tensile strength varied significantly between edible films made from rice starch with that of wheat and corn. Melting temperature (Tm) of wheat and corn starch films was higher than rice starch films (152.77 °C). Thus, rice starch in combination with different additives such as chitosan, emulsifier, and red palm oil, which improve the properties of rice starches have been chosen to coat dried walnut kernels. The coated walnuts were significantly (p ≤ .05) lighter than the control group. Results on different functional ingredients also showed significant variations, for example; yellowness of walnut in the presence of chitosan was lower among the coating formulas (p ≥ .05). However, the variations in textural characteristics of walnuts with different coating formulas remained nonsignificant (p > .05). Practical applications Rice based edible coating added with chitosan can be used to extend the shelf life of walnut kernels. These coated walnuts can be safely distributed or sold in tropical countries where the surrounding relative humidity and temperature is high. Edible coating serves as a barrier which reduces the effect of oxygen, moisture and temperature (most important factors of rancidity) on nuts. The application of starch‐based coating for walnuts will also help to reduce storage space as removing the husk (green layer) and shell of walnuts (wooden layer) results in less space requirements. Furthermore, the coated walnuts can be stored at room temperature and requirement for refrigerated system can be eliminated, hence the cost of storage is minimized.

Celiac is the second most important issue in food sensitivities. The only treatment for celiac is a lifetime avoidance of consuming gluten. As pretzels are one of the most popular snacks in the world, making gluten-free pretzels is a market need. To produce gluten-free products, it is important to optimize the ingredients of the formulation. This research focused on optimization of the leavening agents of the most popular commercial hard pretzel formulation in which wheat flour is replaced with brewer's rice flour. This research also attempts to explain the effect of leavening agents in products containing no matrix molecules such as gluten. Response surface methodology via the central composite design was used to optimize the effects of yeast and bicarbonate of soda on the hardness (cutting strength), fracturability (brittleness), surface color, lateral expansion, expansion ratio, specific length, density (bulk, particle, material), porosity (open, close, total), water absorption index, water solubility index, water holding capacity, oil absorption index and oil holding capacity of gluten-free hard pretzel. The optimized results indicated that the gluten-free pretzel requires 8.05g yeast and 2.59g bicarbonate of soda for every 500g of brewer's rice flour. PRACTICAL APPLICATIONSThe study investigated the effect of leavening agents (yeast and sodium bicarbonate) which are critical ingredients affecting the quality characteristics, consumer preference and palatability of gluten-free hard pretzel when typical soft wheat flour was replaced with a gluten-free flour like rice or brewer's rice flour. The result guides the gluten-free industries on the importance of using the suitable amount of leavening agents for production of acceptable physicochemical and textural properties of not only hard pretzel, but also for other low moisture cereal products as well. The findings also introduce the usage of brewer's rice, a by-product of rice milling industry as one of the ingredients for the production of value-added products for all consumers' especially the celiac sufferers who need to find more reasonable price products compared to gluten ones.