This study was conducted to examine the utilization potential of grape stems as nutritional supplements, and the physiological functionalities of 70% ethanol extracts from grape fruit stem (GFS) were investigated. Each experimental group was prepared with different methods and included GFSF (GFS prepared with freeze drying), GFSI (GFS prepared with infrared drying), GFSH (GFS prepared with heat air drying), and GFSS (GFS prepared with sun drying). The respective yields of freeze-dried powders for the GFSF, GFSI, GFSH, and GFSS were 59.27%, 57.13%, 58.57%, and 58.87%, respectively. Total polyphenol contents in the GFSF were significantly greater than those in the other extracts, whereas total flavonoid contents in the GFSI were higher than those in the other extracts. The contents of proanthocyanidin-related substances were ranked in the order of GFSF > GFSI > GFSH > GFSS. The thin layer chromatograph (TLC) analysis of catechin showed that the GFSF, GFSI, GFSH, and GFSS were detected in the same band. The electron donating ability with 500 μg/mL (w/v) solutions of GFSF, GFSI, GFSH, and GFSS amounted to 93.14%, 93.07%, 92.64%, and 86.95%, respectively, and the reducing powers (OD 700) were 1.933, 1.765, 1.455, and 1.200 absorbance units, respectively. Additionally, the ABTS radical scavenging ability showed the same tendency that was observed with the electron donating ability and reducing power. The angiotensin-converting enzyme (ACE) inhibitory activity and tyrosinase inhibitory activity with 500 μg/mL (w/v) solutions of GFSF and GFSI were higher than those of GFSH and GFSS. In conclusion, the infrared drying technique is the superior method for the enhancement of biological activity for by-product utilization.

이전 연구에서 포도 품종별 및 부위별 생리활성 물질을 분석한 결과 MBA 품종의 송이줄기 부위에서 transresveratrol 함량이 다른 품종에 비해 수십배 높았다. 이를 바탕으로 포도주 제조 시 버려지는 비가식 부위인 송이줄기 를 농도별로 첨가해 발효 중 발효액 및 포도주의 폴리페놀 함량을 조사하였다. 송이줄기 첨가량에 따른 발효액의 발효 중 적색도, 총안토시안 함량, 총폴리페놀 및 탄닌 함량은 발효후기로 갈수록 송이줄기 첨가에 따라 유의적으로 증가 하였고, 포도주에서도 같은 경향을 보였다. 반면 포도주의 휘발산 함량은 송이줄기 첨가량이 증가할수록 감소하는 경향을 보였다. 발효액 및 포도주의 폴리페놀 성분을 분석 한 결과 catechin(8.16∼23.08 mg/L)함량이 가장 높았으며 gallic acid(2.32∼3.28 mg/L), trans-resveratrol(1.38∼3.27 mg/L)및 ferulic acid(1.51∼1.59 mg/L) 순서로 함량이 높았 다. MBA 포도주의 항산화활성을 DPPH IC50로 측정한 결과 송이줄기 함량에 비례해 활성이 증가하였으며, 송이줄기 5% 첨가한 포도주(12 mg/L)는 ascorbic acid의 DPPH IC50 (67 mg/L)보다 낮은 농도에서 높은 항산화활성을 나타내었 다.