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Hot-pressure extraction was utilized in this study to extract proteins from chicken bones at 130 °C. The obtained extracts were further used to prepare gelatin gels. Results demonstrated that the extraction time can significantly affect the composition of the chicken bone extracts (P 30 KDa was only visible in the extracts collected between 40 and 60 min. The highest contents of hydroxyproline, imino acids, and hydrophobic amino acids were all achieved in the chicken bone extracts after 120 min of extraction, being 3.9, 7.7, and 16.0 mg/g, respectively. The prepared gelatin properties were evaluated in terms of viscosity, storage and loss modulus, stability, gel strength, and their microstructures. Results indicated that gelatins made from chicken bone extracts of 20, 40, and 60 min extraction had better properties compared to that of 90 and 120 min. Significant correlations were identified between gelatin's composition and properties (P < 0.05). The abundance of proteins with MW of

BACKGROUND The cost of peptone is often a major contributor to costs in the fermentation industry. A novel method for preparation of peptone from chicken bone residue by using natural pancreas as catalyst was developed in this study, aiming to provide a way to convert waste into valuable peptone. RESULTS The molecular weight of chicken bone extract (CBE) hydrolyzed with pancreas or its combination with trypsin ranges between 100 and 1000 Da after 4 h of hydrolysis. CBE hydrolyzed with pancreas (5%, w/w) for 4 h shows higher degree of hydrolysis (DH) (23.60%) than that of 0.5% trypsin, and higher polypeptides and free amino acids content than that of 0.5% trypsin and 1% pancreas. Thus, it was selected for yeast, bacteria and fungi incubation, with commercial casein peptone as a control. Saccharomyces cerevisiae shows a similar growth curve in both media during 36 h incubation. Although Bacillus subtilis shows a longer lag phase (14 h) in chicken bone hydrolysate (CBH) than in the control (6 h), significantly higher OD600 in CBH was obtained after 24 h incubation (P

Hot-pressure extraction (HPE), which is regarded as a "green" technology, was applied to extract nutrients (protein, collagen, and minerals) from chicken bone residue (CBR). Amino acids (AA), color, and volatile flavor compounds of chicken bone extract (CBE) were also investigated. Results showed that contents of protein, total soluble solids, minerals, and collagen of CBE were positively correlated with extraction time and temperature. High ratios of protein (83.51%) and collagen (96.81%) were obtained with 135 °C and 120 min. Essential AA accounted for 31.03% to 47.73% of total AA in CBE. The percentage of bitter AA in TAA decreased from 28.94% to 25.02% at 0 min to 20.19% and 21.41% at 120 min, although fresh AA increased from 46.35% to 50.84% (0 min) to 53.14% (120 min) at 130 and 135 °C, respectively, indicating CBE was nutritionally beneficial with good flavor. Color and volatile flavor of CBE improved significantly after extraction, although calcium in CBE (4.2 to 4.8 mg/100 g) was relatively low compared with that of CBR (1078 mg/100 g). It can be concluded that HPE is a promising way to transform CBR into a nutritious flavorant substrate, but it is not an efficient way to extract calcium.