Kazunori Hironaka

Ascorbic acid enrichment of whole potato tuber by vacuum-impregnation

The aim of this study was to evaluate the use of vacuum-impregnation (VI) for enriching the ascorbic acid content of whole potatoes. Whole potatoes were immersed in a 10% ascorbic acid (AA) solution. A vacuum pressure of 70cm Hg was applied for 0-60min, following atmospheric pressure restoration for 3h, while samples remained in the VI solution. AA concentrations of potatoes were measured using HPLC. The effects of cooking and storage time in subsets of the fortified samples were also evaluated. Results indicated that the AA concentration of whole potatoes increased with vacuum time (max 150mg/100g fr. wt.). In addition, a steam-cooking study showed that 100g of the 25min steam-cooked VI potatoes could provide adults with 90-100% of the recommended daily allowance of AA (100mg). The storage study showed that VI whole potatoes had a relatively high AA concentration (50mg/100gfr. wt.), even at 14days of storage at 4°C. This study indicated that VI treatment of whole potatoes was useful for enriching the AA content.

Effect of Holding Temperature on the Structures of Mung Bean Starch Gels and Noodles

ABSTRACT The effect of storage temperatures (-10, +1, and +10°C) on the structural organization of mung bean starch gels and noodles was studied by acid hydrolysis, X-ray diffractometry, and gel-permeation chromatography. The gels showed higher susceptibility to acid compared with the noodles as shown by the rate constants of the first stage of hydrolysis (k = 5.37–12.17 × 10-2/day and k = 4.19–4.61 × 10-2/day for gels and noodles, respectively). Acid hydrolysis showed no difference in the amount of resistant residues of both gels (42–46%) and noodles (44–45%), except for gels (38%) stored at -10°C. The acid-resistant residues of both the gels and noodles had a B-type X-ray diffraction pattern (major reflections at 2θ = 19, 24, and 25°). The acid-resistant residues of the unstored sample and those stored at -10°C for both gels and noodles contained chains with DP 46–54 and after debranching yielded two peaks with DP 29–39 and DP 15–19. The acid-resistant residues of gels and noodles stored at +1 and +10°C...