Recently, LEDs with various light qualities have been used in closed plant factories, and they are known to have different effects on the growth and quality of crops. Therefore, this study was conducted to investigate the change in growth and quality in mini red romaine lettuce using LEDs with various light qualities. Wide red spectrum (WRS)-LEDs, blue (B)-LEDs, blue + red (BR)-LEDs, red (R)-LEDs, and white (W)-LEDs were used as the artificial light sources. Regarding growth, the R-LED treatment showed the most positive effect, but the leaf shape was not normal and the Hunter b* value was not suitable because it was higher than that of the other treatments. The Hunter a*, SPAD, and NDVI values of the B- and BR-LED treatments were effective, but this was not the case for those of the R- and W-LED treatments. The anthocyanin reflectance index 1 (ARI1) was 20 times higher in the B-LED treatment than in the R-LED treatment, and the ascorbic acid content was the highest in the WRS-LED treatment. In the sensory evaluation, bitterness and sweetness showed opposite tendencies. Regarding the overall preference, the BR-LED treatment received the highest score. Correlation analysis showed that the bitterness was closely correlated with the anthocyanin content and leaf color. Taken together, BR-LEDs provided a good top fresh weight, dark red leaves, and high anthocyanin and ascorbic acid contents, with the highest overall preference; therefore, BR-LEDs were the most suitable for the cultivation of mini red romaine lettuce.

This study aimed to examine the effect of modified atmosphere (MA) storage on the quality and storability of romaine lettuce. Whole and fresh-cut romaine lettuce were packaged with 1300; 10,000; 50,000; 100,000 cc m⁻²·day⁻¹·atm⁻¹ O₂ transmission rate (OTR) films and stored at 2 or 8 °C for 15 days. The respiration and ethylene production rates before pre-cooling were higher in fresh-cut lettuce than in whole romaine lettuce. The reduction in fresh weight for whole and fresh-cut romaine lettuce during storage was less than 0.5%. The CO₂ concentration was less than 2%, except for the 1300 cc treatment (at 8 °C for whole and fresh-cut lettuce) and 10,000 cc (in fresh-cut lettuce). At the end date of storage, the overall quality of the whole lettuce was good, the off-odor was lower in the 10,000 cc treatment, and the 50,000 cc treatment at 8 °C led to good overall quality in the fresh-cut lettuce. The chlorophyll content of the whole lettuce was maintained at a higher level in the treatment of 10,000 cc at 8 °C, while it was higher in the 50,000 cc treatments at 2 and 8 °C in the fresh-cut lettuce. Correlation and PCA confirmed that the main factors affecting the storability and quality of romaine lettuce were fresh weight loss rate, off-odor, and the concentration of CO₂. In addition, the storage characteristics of whole and fresh-cut lettuce were opposite to 0 in PC1 and PC2, indicating that the storage characteristics were different depending on the processing type.

Green asparagus is vulnerable to thrips that carry microorganisms and cause deterioration in quality. The effects of 60% CO₂ treatment, which is used to kill thrips, combined with perforated (P) or modified atmosphere (MA) packages during cold storage, on the sensory quality and physiological–biochemical characteristics of asparagus were investigated. MA packaging yielded an asparagus shelf-life five days longer than P packaging. The 60% CO₂ treatment for 48 h at 4 °C packaged with MA film (CO₂-48 h-4 °C-MA) showed a lower number of aerobic bacteria, yeast, and mold. Yellowing of asparagus was retarded, as shown by higher hue angle and chlorophyll content and lower chlorophyllase activity. Also, CO₂-48 h-4 °C-MA treatment inhibited the reduction of soluble solids content in asparagus. Likewise, all high CO₂ treatments showed lower electrolyte leakage (EL), with CO₂-48 h-4 °C-MA demonstrating the minimum EL. The effectiveness of high CO₂ on maintaining sensory qualities was observed, with a score higher than 3.0. In conclusion, CO₂-48 h-4 °C-MA treatment during cold storage was effective for maintaining post-harvest sensory qualities and physiological–biological traits of asparagus, and provided strong inhibition of microflora growth during the storage period.

Water loss, interwoven with other factors, is identified as the cause of chilling injury to sweet peppers. The breaker stage is the most vulnerable of all maturity stages. The purpose of this study was to see if increasing the storage relative humidity (RH) reduces the chilling injury and to compare its effect on breaker-stage fruits to red-ripe fruits at a normal RH. The fruits were stored at 5 °C with a RH of 98 ± 2% and 70 ± 6% for high and low RH, respectively. After 15 days of cold storage, the fruits were moved to ambient conditions for 3–5 days for chilling injury symptoms to appear. The results showed that high RH storage reduced fruit water loss by 4–4.5% compared to low RH storage, resulting in fewer chilling injury symptoms regardless of fruit maturity stage. Due to the increased RH, cell membrane damage indicators such as electrolyte leakage, MDA, respiration, and ethylene production rates were shown to be reduced, while brix and color were well maintained, indicating reduced or stopped senescence. Furthermore, DPPH antioxidant activity and vitamin C were retained and optimized. The microbiological analyses also showed that a high RH may not promote the growth of microorganisms as quickly as may have been thought. Finally, the findings of this study indicate that breaker-stage peppers stored at a high RH may be less susceptible to chilling injury than red-ripe peppers stored at a low RH.

In this study, an experiment was conducted to suggest optimal daytime temperature and light intensity for cucumber scion and rootstock production in a plant factory with artificial light. Plant growth of cucumber scions and rootstocks at a day/night temperature of 26/18 °C and photosynthetic photon fluxes of 50, 120, 190, 260, 330, and 400 μmol·m⁻²·s⁻¹ was investigated. Plant growth under daytime temperatures of 25/18, 26/18, 27/18, and 28/18 °C at a photosynthetic photon flux of 260 μmol·m⁻²·s⁻¹ was investigated. As the photosynthetic photon flux increased, hypocotyl length was shortened in cucumber scions and rootstocks, but Dickson quality index, compactness, and Seedling Health Index were improved. As the daytime temperature increased, the hypocotyl length of cucumber scions increased, but the quality of seedlings decreased. The root growth of scions decreased as the daytime temperature increased. As for the correlation between the major growth indicators, Dickson quality index, compactness, and Seedling Health Index showed a high correlation of more than 0.8 in stem diameter, leaf, and root weight. Therefore, it is judged that it is most efficient to maintain the photosynthetic photon flux at 260 μmol·m⁻²·s⁻¹ throughout the year and adjust the daytime temperature to 25 to 28 °C according to the season for farms and commercial nurseries that produce cucumber seedlings by installing plant factories with artificial light.

This study investigated the effects of supplemental inter-lighting on paprika (cv. Nagano RZ) in South Korea in summer using various LED light sources. The following LED inter-lighting treatments were used: QD-IL (blue + wide-red + far-red inter-lighting), CW-IL (cool-white inter-lighting), and B+R-IL (blue + red (1:2) inter-lighting). To investigate the effect of supplemental lighting on each canopy, top-lighting (CW-TL) was also used. Additionally, a control without supplemental lighting was included for comparison. Significant variations were observed in the plant growth indexes 42 days after treatment. The SPAD values and total chlorophyll content in the last period of cultivation were significantly higher than those of the control. In November, the marketable fruit yield was significantly higher than that of the control. QD-IL, CW-IL, and CW-TL resulted in significantly higher values of total soluble solids than the control, and CW-IL resulted in higher values of ascorbic acid content than the control. Regarding the economic analysis, CW-IL resulted in the highest net income rate (12.70%) compared with the control. Therefore, the light sources of CW-IL were assessed as suitable for supplemental lighting due to the highest total soluble solids, ascorbic acid content, and net income rate obtained.