Punnanee Sumpavapol

Quality changes of sea bass slices wrapped with gelatin film incorporated with lemongrass essential oil.

Microbiological, chemical and physical changes of sea bass slices wrapped with gelatin film incorporated with 25% (w/w) lemongrass essential oil (LEO) during storage of 12 days at 4 °C were investigated. Sea bass slices wrapped with LEO film had the retarded growth of lactic acid bacteria (LAB), psychrophilic bacteria and spoilage microorganisms including H₂S-producing bacteria and Enterobacteriaceae throughout storage of 12 days in comparison with the control and those wrapped with gelatin film without LEO (G film) (P<0.05). Lowered changes of colour, K value, total volatile base nitrogen (TVB) and TBARS value were also found in LEO film wrapped samples, compared with those wrapped with G film and control, respectively. Therefore, the incorporation of LEO into gelatin film could enhance the antimicrobial and antioxidative properties of the film, thereby maintaining the qualities and extending the shelf-life of the sea bass slices stored at refrigerated temperature.

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.

Quality of Kapi, Salted Shrimp Paste of Thailand, Inoculated with Bacillus spp. K-C3

ABSTRACT The use of Bacillus spp. K-C3, isolated from commercial Kapi, salted shrimp paste of Thailand, as the starter culture for Kapi production, at different levels including 102, 104, and 106 CFU/g dry weight sample named Kapi-B2, Kapi-B4, and Kapi-B6, respectively, in comparison with naturally fermented Kapi (Kapi-C) was studied. All inoculated samples exhibited higher extent of proteolysis and lipolysis as indicated by higher trichloroacetic acid (TCA)-soluble peptide, degree of hydrolysis, and free fatty acid content in the final products. The greater rate of fermentation in the inoculated samples directly affected characteristics of Kapi and yielded Kapi with browner color and enhanced lipid oxidation as indicated by peroxide value (PV) and thiobarbituric acid reactive substance (TBARS) values. Increased antioxidative properties, including 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical scavenging activities, and ferric reducing antioxidant power (FRAP), were obtained in Kapi with added inoculum. Moreover, those inoculated samples also contained higher intensity of volatile compounds, in which N-containing compounds, mainly pyrazine derivatives, were dominant. Kapi-B4 and Kapi-B6 showed the highest extent of these aforementioned values compared with Kapi-C and Kapi-B2. Therefore, inoculation with Bacillus spp. K-C3 at the level higher than 104 CFU/g dry weight sample is a potential means to accelerate the fermentation rate and yielded Kapi with preferable characteristics.