Features of Microwave Heating on Breaking Properties of Confectionery in Low Moisture

Abstract

The e#ect of microwave heating on breaking properties of confectionery was studied by using two methods. One method (I) used the baked products as cookies of which material contained wheat-flour, butter and low content of water. The other (II) used commercial confectionery heated by microwave after moisture absorption. (+) The breaking energy of the microwave heating products was triple higher compared with the conductive, and was approximated to the value of the conductive products of which material contained higher water about +*῏,*ῌ. In the sensory evaluation, the texture characteristic of microwave was estimated to be hard, not short, di$cult crunch and chewy. (,) A high, positive correlation was obtained between the breaking properties and the starch gelatinization values, and then a paste material was suggested to be an important factor for hardening. (-) A moisture absorption sample contained about +/ῌ water, in the microwave heating, began increasing starch gelatinization and breaking properties. It is assumed that the temperature raising behavior in low moisture might accelerate the physical properties changing.

Relationship between monolayer and multilayer water contents, and involvement in gelatinization of baked starch products

“…It was distributed from 3.6 to 5.3 g/100 g dry matter for adsorption and from 5.1 to 8.2 for desorption; thus, little discrepancy was observed between different baking methods, and the W m was higher for desorption than for adsorption. As gelatinization characteristics also remained unchanged even with use of a different heating method (Higo and Wada, 2005), the combination microwave heating method was suggested to be a good, less time-consuming substitute for the gas oven heating method.…”

“…Finally, after centrifugation at 1900g for 20 min, they were separated into the supernatant and precipitate. Five-milliliter samples of the supernatant were mixed with 0.5 mL of I 2 solution (a mixture of 0.2% I 2 and 2.0% KI) and the absorbance at 660 nm was measured (Wada et al, 1999;Higo and Wada, 2005). Starch solubility was calculated as follows: starch solubility (%) = (absorbance of the supernatant at 660 nm) Â 100/(absorbance of the authentic gelatinized wheat starch solution).…”

“…The weight of water-soluble substances in the supernatant was calculated from the absorbance at 660 nm by comparison with authentic gelatinized wheat starch solutions that had been heated in boiling water for 30 min. Swelling capacity was calculated as follows (Wada et al, 1999;Higo and Wada, 2005): swelling capacity (-) = (weight of precipitation)/[(weight of defatted sample) À (weight of soluble substances in supernatant)]. Fig.…”

“…To prepare the defatted product, the products were put into a chloroform-methanol solvent (2:1) and refluxed for 4 h at 80°C prior to the water sorption assay. After evaporating the solvent, the dried powder was used for this assay as described below (Higo and Wada, 2005). A 5 ml of 25 mg% amyloglucosidase (A-7420; Sigma, St. Lous, MO) (58 unit/mg) in 2 M acetic acid buffer (pH 4.5) was added to 100 mg of the defatted powder and incubated at 37°C for 160 min.…”

Analysis of water layers and the extent of gelatinization for commercial starch products

“…The weight of water-soluble substances in the supernatant was calculated using the iodine assay, based on the absorbance at 660 nm (as described in Section 2.7) and its contribution was estimated to be small. Swelling capacity was calculated as follows (Wada et al, 1999;Higo and Wada, 2005;Sato et al, 2010): swelling capacity (-) = (weight of the precipitation)/[(weight of defatted powder applied) À (weight of water-soluble substances in the supernatant)].…”