Fruit Quality and Volatile Compounds of Greenhouse Sweet Pepper Fruits as Affected by LED Spectrum of Supplemental Interlighting

Abstract

Seasonal low light intensity and short photoperiods lead to decreased yield, size, and quality of fruits in the Northern Hemisphere. Recently, supplemental lighting using LEDs has been introduced to overcome such problems. However, most studies have focused on plant growth or fruit yield but not on taste. This study aimed to evaluate the quality and volatile compounds of greenhouse sweet pepper fruits under three different light conditions: natural light only (NL), red and blue (RB) interlighting, and RB interlighting with additional FR (RBFR). Sweet peppers (Capsicum annuum L.) were grown in a Venlo-type glasshouse. The red to blue ratio of the LED was 8:2, and the combined light intensity was adjusted to 100 μmol m-2 s-1 at a distance of 20 cm. The spectral intensity of FR was 60 μmol m-2 s-1. The average daily light integral (DLI) during cultivation was 16.6 mol m-2 d-1. The size, color, firmness, and soluble sugar concentration of the harvested fruit were investigated, and sensory evaluation was conducted by nine trained panelists. Individual fruit fresh weights were higher in the order of RBFR, NL, and RB, with mean values of 219.1, 201.7, and 197.4 g, respectively. Additionally, the compositions of volatile compounds demonstrated a distinct clustering pattern by light treatments, implying that the LED interlighting spectra affected the overall taste of sweet pepper fruits. The sensory evaluation indicated that sweetness was higher in the order of RBFR, RB, and NL, with values of 5.28, 4.36, and 3.72, respectively. The soluble sugar results showed the same order as that for the sensory evaluation of sweetness, i.e., RBFR, RB, and NL, with values of 5071, 4647, and 3978 μg FW-1, respectively. Based on these results, it can be seen that adding FR to RB interlighting could improve the fruit quality attributes, fruit taste perception, and soluble sugars of sweet peppers compared to those under RB and NL.

광은 작물의 생산성과 품질에 직접적인 영향을 준다. 온실 재배에서 보광은 동절기에 상대적으로 짧은 일조량을 보충하고 연중 생산 및 과실 품질 유지를 위해 도입되고 있다. 그러나 적색+청색 및 원적색광을 이용한 보광이 착색단고추의 과실 품질과 향에 미치는 영향은 제한적이다. 본 연구는 자연광, 적색+청색 보광, 적색+청색+원적색 보광 처리 조건에서 재배한 착색단고추 과실의 형태, 크기, 경도, 색, 맛 품질을 평가하였다. 수확 후 각 과실의 무게, 과장, 과폭, 색을 측정하였고, 당, 산, 향 성분을 분석하였다. 실험 결과, 과실 생체중은 적색+청색+원적색 보광, 자연광, 적색+청색 보광 순서로 높았으며, 과실의 당성분과 패널 테스트의 단맛 점수 및 총 선호도 역시 적색+청색+원적색 보광, 적색+청색 보광, 자연광 순으로 높았다. 또한 광 처리별로 과실의 향미 성분이 다르게 군집화 되었고, 결과적으로 보광 처리 광질이 과실의 전반적인 맛과 선호도에 영향을 미쳤을 것으로 사료된다. 본 연구는 일반적인 적색+청색 보광에 원적색광을 추가할 경우에 착색단고추의 생산성과 전반적인 과실의 맛과 품질을 개선할 수 있음을 증명하였다.