Desorption of nutrients and flavor compounds formation during the cooking of bone soup

In order to identify the effects of varying cooking time on the quality of bone soup, the diversification of nutrient profiles and flavor compounds in bone soup prepared within 10 h' cooking was studied. The Kjeldahl method, inductively coupled plasma mass spectrometry (ICP-MS), automatic amino acid analyzer (AAA analyzer), high performance liquid chromatography (HPLC), solid phase microextraction-gas chromatography-mass spectrometry (SPME-GC-MS) were applied to determine the changes of crude protein, minerals, free amino acids (FAAs), 5′-nucleotides, and volatile compounds in the soup, respectively. During the 10 h cooking, the concentration of nutrients and flavor compounds reached their maximum and then decreased, except for minerals, which continued to increase in concentration. 18 FAAs were identified in all samples, which were related with I-collagen hydrolysis. Taste FAAs contributed little to the flavor of soup. Bitter amino acids increased significantly (P < 0.05) and IMP + GMP reached maximum concentration at the seventh hour of cooking. The main flavor compounds of bone soup were aldehydes, which increased significantly (P < 0.05) during boiling. Samples taken at the fourth and fifth hours contained the richest profile of volatile flavor compounds. In general, for high-quality bone soup, cooking time should be limited to achieve an appropriate balance between nutrient dissolution and flavor formation.