Samart Sai-Ut

Effect of Drying Methods on Odorous Compounds and Antioxidative Activity of Gelatin Hydrolysate Produced by Protease from B. amyloliquefaciens H11

Gelatin hydrolysates with antioxidative activity produced by protease from Bacillus amyloliquefaciens H11 with different hydrolysis times were prepared. Alpha-amino group content and antioxidative activities increased with increasing hydrolysis time (p < 0.05). When gelatin hydrolysate prepared with hydrolysis time of 3 h (GH-3H) was subjected to freeze drying and spray drying, the powder obtained from spray drying showed a decrease in antioxidant activity as measured by DPPH and ABTS radical scavenging activities, ferric-reducing antioxidant power, and metal chelating activity. Spray-dried gelatin hydrolysate (GH-3H-SD) showed higher whiteness with lower fishy odor and off-odor associated with fermentation. This was concomitant with the decreases in several odorous compounds in the sample, except for nonanal, which was higher in comparison with the powder obtained by freeze drying. Thus, spray drying could be an effective drying method to improve color and reduce undesirable odor of gelatin hydrolysate.

Gelatinolytic Enzymes from Bacillus amyloliquefaciens Isolated from Fish Docks: Characteristics and Hydrolytic Activity

Fifty-five bacteria with gelatinolytic activity were screened from over 500 isolates obtained from fishing docks in Songkhla, Thailand. Based on 16S rRNA gene sequence analysis, 3 selected strains (K12, O02, and S13) were identified as Bacillus cereus with 99.8% similarity. Three other stains (D10, G02, and H11) were identified as Bacillus amyloliquefaciens with 99.7% similarity. Gelatinolytic enzymes of the D10, G02, and H11 strains were precipitated using ammonium sulfate precipitation, followed by dialysis with an increase in purity between 19-34-fold. Maximal gelatinolytic activities towards fish gelatin were attained at 50°C and pH 7.5. Metallo- and serine-gelatinolytic enzymes were dominant for all 3 strains. All gelatinolytic enzymes showed similar hydrolysis towards fish gelatin to commercial Alcalase, but higher hydrolysis was found in the formers within the first 60 min. Therefore, gelatinolytic enzymes from selected B. amyloliquefaciens strains can be used for production of fish gelatin hydrolysate.