Effect of Extrusion Cooking on the Physicochemical Properties of Poria cocos

This study aimed to investigate the effects of extrusion cooking at different temperatures on the physicochemical properties of Poria cocos, in order to provide a scientific basis for the extrusion cooking of P. cocos and its related products. The physicochemical properties and chemical composition of raw and extruded P. cocos at 60 (PJ60), 80 (PJ80), 100 (PJ100), 120 (PJ120), and 140 ℃ (PJ140) were analyzed. The results indicated that extrusion cooking temperature significantly influenced the particle size, water solubility index (WSI), water absorption index (WAI), and dispersibility of P. cocos powder. The WSI, WAI and dispersibility of P. cocos powder extruded at low temperatures (60–80 ℃) were superior to those at high temperatures (> 100 ℃). However, extrusion cooking caused the color of P. cocos powder to become darker. Compared with untreated P. cocos, low-temperature extrusion cooking (60–80 ℃) significantly increased the content of water-soluble polysaccharides, with PJ60 having the highest value. Total triterpenoid content was significantly higher in all extrusion-cooked samples than in P0, with the highest value being observed in PJ60, and so it was with ethanol-soluble extract content. A total of 38 triterpenoids were detected across the ethanol extracts from all P. cocos samples. The relative total content of triterpenoids common to all samples was the highest in PJ80, and the relative contents of the major terpenoids such as dehydroporinic acid and dehydrotuberic acid were higher in PJ60 and PJ80. Additionally, extrusion cooking produced new triterpenoid compounds, including dehydroeburicoic acid monoacetate, poricoic acid AE, and 25-methoxyporicoic acid A. Extrusion cooking increased the contents of the major volatile components in P. cocos. Furthermore, the contents of off-flavor components were reduced, while the contents of aroma components such as nonanal and phenylacetaldehyde were increased. In summary, low-temperature extrusion cooking (60–80 ℃) effectively improved the contents of water-soluble total polysaccharides, total triterpenoids and ethanol-soluble extract of P. cocos, which may be attributed to the fact that extrusion cooking enhanced WSI, WAI, and dispersibility of P. cocos. In contrast, high-temperature extrusion cooking (> 100 ℃) led to a decrease in the contents of water-soluble total polysaccharides, total triterpenoids and ethanol-soluble extract, indicating that high-temperature processing caused losses of these components. On the other hand, low extrusion cooking temperatures (60–80 ℃) enhanced the dissolution rate of active components from P. cocos with reduced processing losses, thereby preserving its efficacy as a functional food ingredient in extruded foods.