Abstract: 【Objective】In order to optimize the extrusion process conditions, the effects of extrusion operating parameters on nutritional quality, physicochemical properties and volatile aroma components in final products of germinated brown rice compounded of Flammulina velutipes were investigated. The study will provide theoretical basis for quality evaluation and development of functional snack foods. 【Method】 To analyze the effects of extrusion operating parameters on GABA content, soluble dietary fiber content, soluble protein content and radial expansion ratio, germinated brown rice compounded of Flammulina velutipes were extruded to obtain a composite type of puffed products with a twin-screw extruder at different moisture content, extrusion temperature and screw speed conditions. Changes of the amino acids content and physicochemical properties such as hardness, bulk density, water-absorption index, water-solubility index and color difference of germinated brown rice compounded of Flammulina velutipes extrudates were analyzed compared with non-supplemented germinated brown rice products. In addition, the volatile flavor compounds in the puffed products were also analyzed comparatively using electronic nose. 【Result】The quality properties of germinated brown rice compounded of Flammulina velutipes extrudateschanged with the extrusion operating parameters. The GABA content showed a trend from decline to rise as the moisture content kept increasing, dropped sharply as the extrusion temperature increased, and increased at first, but then decreased. With the moisture content, the extrusion temperature and the screw speed increasing, both the SDF content and the soluble protein content had a decline trend after an initial ascent. The radial expansion ratio decreased with the moisture content and the extrusion temperature increasing, while increased first but then decreased as the screw speed continued increasing. The optimal conditions of the extrusion were moisture content 17%, extrusion temperature 140℃ and screw speed 150 r/min from the single factor test. Under these conditions, the content of GABA, SDF and soluble protein were (210.44 ± 0.39) mg·kg^-1, (0.735 ± 0.028) g·100 g^-1 and (1.23 ± 0.01) mg·g^-1, respectively, and the radial expansion ratio of the extruded products was 2.67 ± 0.02. Compared with the un-extruded compounded powder and germinated brown rice extruded products, the total amount of amino acids of germinated brown rice compounded of Flammulina velutipes extrudatesincreased by 1.7% and 2.9%, respectively, and essential amino acid content increased by 2.8% compared with non-supplemented germinated brown rice extrudates, among which, the arginine and lysine content increased by 6.6% and 5.7% respectively, indicating that the addition of Flammulina velutipes powder could increase the amino acid content significantly. The extruded products from germinated brown rice compounded of Flammulina velutipes exhibited lower radial expansion ratio, lower degree of gelatinization, lower water-solubility index and lower L* value, but higher a*, b*and ΔE values than extruded products of non-supplemented germinated brown rice, which indicated that germinated brown rice compounded of Flammulina velutipes extrudates showed greater browning degree. The analytical results of electronic nose showed that the volatile flavor compounds were significantly different between the extruded products from germinated brown rice compounded of Flammulina velutipes and non-supplemented germinated brown rice, which reflected the overall flavor profile of different samples accurately and quickly. 【Conclusion】 The products of germinated brown rice compounded of Flammulina velutipes had comprehensive nutrition, good taste and unique flavor characteristics after the optimization of extrusion technology. Extrusion technology was an effective method to improve the nutritional quality and taste flavor of germinated brown rice.

Key words: Flammulina velutipes, germinated brown rice, extrusion, quality property, electronic nose