Loss Of Molecular Order Research Articles

Extraction, characterization and molecular structure of bovine skin gelatin extracted with plant enzymes bromelain and zingibain.

Bovine skin was incubated with plant enzymes bromelain (B) and zingibain (Z) at the level of 0, 5, 10, 15, 20 and 25 unit/g of skin and gelatin was extracted at 60°C for 6h. Control gelatin was extracted without enzymatic pretreatment. The yield and gel strength were 17.90% and 283.35g for the control samples and 22.26% and 160.88g for B20 samples. The zingibain extracted gelatin (GEZ) samples failed to form gel. Viscosities of GEZ gelatins were significantly (P < 0.05) lower than the gelatins extracted using bromelain (GEB). β and α chains were absolutely degraded in all GEB and GEZ samples. Only smear bands were observed in GEZ gelatins whereas GEB samples revealed presence of low molecular weight polypeptides. Loss of molecular order was noticed in Z5 as elaborated by Fourier transform infrared (FTIR) spectroscopy. Larger particle size, denser and inter-connected irregular network was observed in B20 under scanning electron microscopy. Based on the results obtained, bromelain, particularly at level 20, could be used to obtain a better quality gelatin with higher yield compared to zingibain.

Comparison on structure and physicochemical properties of starches from adzuki bean and dolichos bean

The major carbohydrate in pulse is starch. The structure and physicochemical properties of starches from adzuki bean (AS) and dolichos bean (DS) were systematically compared in this work. Results showed that the differences in morphology (oval to kidney), crystal type (CA-type) and sugar linkage between AS and DS were minor. However, AS had lower amylose content (26.64%) and larger granule size than DS (31.85%). AS showed higher relative crystallinity, ratio of 1047/1022 cm−1, single helix and double helix content (26.27, 0.95, 4.55 and 37.61%) than those of DS (24.08, 0.92, 4.76 and 27.49%, correspondingly), while AS may have loss of molecular order. Moreover, two kinds of anomalous linkages were detected by methylation analysis in AS and DS. These features contributed to higher swelling power, solubility, light transmittance and freeze-thaw stability of AS. Meanwhile, AS exhibited lower pasting and gelatinization temperatures, enthalpy and better pasting stability. The study indicated that amylose content, granular and crystalline structure of AS and DS may be responsible to their different properties. Hence, the study will improve the scientific basis on starches from adzuki bean and dolichos bean, and facilitate their utilization.

Characteristics of Gelatin Extracted from the Swim Bladder of Yellowfin Tuna (Thunnus albacores) as Affected by Alkaline Pretreatments

ABSTRACTGelatins extracted from the swim bladder of yellowfin tuna (Thunnus albacores) using various alkaline pretreatments were characterized. Alkaline mixtures (Na2CO3:NaOH) at different ratios (9:1, 8:2, 7:3, and 6:4) with a concentration of 4% (w/v) were used. The corresponding gelatins termed “G1,” “G2,” “G3,” and “G4” had yields of 9.78, 14.91, 35.96, and 13.60% (dry weight basis), respectively. All gelatins had α-chains as the major components. Fourier transform infrared spectra of obtained gelatins revealed the significant loss of molecular order of the triple-helix. G3 having the highest imino acid content and exhibited the highest gel strength (p < 0.05), compared with others. The microstructure of G3 gel was finer with smaller voids, compared with others. With increasing proportion of NaOH, the L*-value of gelatin gel increased with coincidental decrease in ΔE*-value. Gelling and melting temperatures of swim bladder gelatin were 12.3–15.1 and 21.3–22.3°C, respectively.