Effects of Preharvest Salicylic Acid Treatment on Chilling Injury Alleviation and Quality of Lemon Basil and Holy Basil during Cold Storage

Suriyan Supapvanich1* Pratumtip Wongsuwan1, Bunwat Mahasap1, Rachadakorn Polpakdee1, and Panida

Boonyaritthongchai2

ABSTRACT

The objective of the study was to investigate the effect of preharvest salicylic acid (SA) spraying on physical quality and chilling injury of lemon basil and holy basil during cold storage. SA solution at the concentration of 0, 1.0 and 10.0 mM was sprayed on the both herbs before harvesting 24 h and herbs were then stored at 8 ± 2 °C for 4 days. Visual appearance, weight loss, chilling injury score, lightness (L*), greenness (-a*) and yellowness (b*) were determined. Preharvest SA treatment alleviated chilling injury and reduce the loss of –a* value during storage which the best result was found in 10.0mM SA treatment; however, a tip burn was detected. SA had no effect on the changes in L* and b* value of the both herbs. In conclusion, preharvest SA spraying effectively alleviated chilling injury in lemon basil and holy basil during cold storage.

Key Words: Lemon basil, holy basil, salicylic acid, cold storage, preharvest treatment * Corresponding author; e-mail address: kusuriya@kmitl.ac.th 1Department of Agricultural Education, Faculty of Industrial Education, King Mongkut’s Institute of Technology Ladkrabang, 1 Chalongkrung road, Ladkrabang, Bangkok 10520 2Postharvest Technology Program, School of Bioresources and Technology, King Mongkut's University of Technology Thonburi, Bangkhuntien campus, Bangkok 10150

INTRODUCTION Lemon basil (Ocimum × citriodourum) and holy basil (Ocimum sanctum) have been used as culinary herbs in Asian foods including Thai food for a long time. The demand of these herbs has been recently continued. The main postharvest problems limiting their quality and shelf-life during storage are spoilage and chilling injury. Wongsheree, et al. (2009) reported that lemon basil and holy basil are relatively higher sensitivity to chilling temperature than sweet basil which the leaf darkening

occurred within 24 h during storage at 4 C. Theoretically, chilling injury is accompanied by the dysfunction of membrane and the loss membrane integrity caused by low temperature above freezing point which these also related to lipid peroxidation and the accumulation of free radicals (Wills, et al., 2007). Salicylic acid (SA) is accepted as a save natural chemical compound for postharvest application (Supapvanich and Promyou, 2013). SA is a simple plant phenolic compound which known as an endogenous signal molecule modulating both biotic and abiotic stresses (Asghari and Aghdam, 2010). SA induces the expression of defense genes leading to the reduction of lipid peroxidation and membrane senescence (Kazemi, et al., 2011). In postharvest application, SA improves storability in many kinds of fruit and vegetables such as peach (Khademi and Ershadi, 2013; Tereen, et al., 2012), sweet cherry (Yao and Tian, 2005; Xu and Tian, 2008) and asparagus (Wei, et al., 2011). Thus, the objective of this work was to investigate the preharvest SA application on chilling injury alleviation and physical quality of lemon basil and holy basil during cold storage.

MATERIALS AND METHODS 1. Materials and experiment

Lemon basil (Ocimum × citriodourum) and holy basil (Ocimum sanctum) were grown at Department Agricultural Engineering garden, King Mongkut’s Institute of Technology Ladkrabang. The herbs at 60 days after grown were sprayed with SA solution at the concentration of 0. 1.0, and 10.0 mM and after spraying for 24 h, the both herbs were then harvested and stored at 8 ± 2 °C for 4 days. Visual appearance, weight loss, chilling injury score, superficial colour (L*, -a* and b*) were monitored. 2. Visual appearance weight loss and superficial colour measurements

Both herbs were taken picture every day of storage to determine the change in visual appearance. The herbs were weighted in everyday and the weight loss during storage was calculated by comparing with the weight at initial day of storage. The data was present as the percentage of weight loss (% weight loss).

Superficial colour such as L*, -a* and b* values of the both herbs were measured using CR-300 Chroma Meter (Konica Minolta Sensing Americas, Inc.). 3. Chilling injury score

Chilling injury score was evaluated using 8 semi-trained panels. A 5 hedonic scaling test was chosen which scale 1 is no chilling injury symptom, scale 3 is 30% chilling injury symptom and scale 5 is more than 50% chilling injury symptom. 4. Statistical analysis

The data were analyzed using analysis of variance (ANOVA) at P > 0.05. Significant differences among mean values from ANOVA were determined by Duncan’s multiple range tests. All statistical analyses were performed using SPSS Software Version 12 (SPSS Inc., Chicago, IL, US).

RESULTS AND DISCUSSION Figure 1 shows the visual appearance of lemon basil and holy basil at day 0 and day 4 of

storage. We found that preharvest SA spraying alleviated chilling injury symptom of both herbs during cold storage. A slight chilling injury symptom was found in the lemon basil treated with 10.0 mM SA and no chilling injury was detected in holy basil treated with 10.0 mM SA during storage for 4 days. However, a tip burn was found in both 10.0 mM SA treated herbs. Similarly the results show in Fig. 2 which the lowest chilling injury score of both herbs was detected in 10.0 mM SA treatment. The control of both herbs had higher chilling injury score than other treatments (P > 0.05). Chilling injury alleviation in plants by SA application has been described by Sayyari, et al. (2009) and Yang, et al. (2012) which SA modulates antioxidant systems, reduces lipid peroxidation and maintains membrane integrity leading to chilling tolerance.

Figure 1. Visual appearance of lemon basil (A) and holy basil (B) treated with SA and stored at 8 ± 2

C for 4 days.

Day 0, Control Day 0, 1 mM SA Day 0, 10 mM SA

Day 4, Control Day 4, 1 mM SA Day 4, 10 mM SA

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Figure 2. Chilling injury score of lemon basil (A) and holy basil (B )treated with SA and stored at 8 ± 2

C for 4 days. Each bar represents the mean ± S.D. of four replicates.

Weight loss of the herbs increased continuously during storage (Fig. 3). The weight loss of both SA treated lemon basil and holy basil was slightly higher than the control; however, no significant difference in each treatment was found. Although it is widely recognized that the increase in weight loss is concomitant with the increase in chilling injury severity, the change in weight loss of both herbs in this work did not relate to the chilling injury symptom.

Figure 3. Weight loss (%) of lemon basil (A) and holy basil (B) treated with SA and stored at 8 ± 2 C for 4 days. Each bar represents the mean ± S.D. of four replicates.

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Figure 4 show the changes in superficial colour of the both herbs during storage. We found that SA treatments had no effect on the change in L* and b* values of the both herbs. As the result shown in Fig 4 B1 and B2, on day 4 of storage, the -a* value of the both 10.0 mM SA treated herbs was significantly higher than that of the other treatments. This shows that SA delayed the loss of greenness during storage. Similarly, Wei, et al. (2011) reported that the loss of greenness in asparagus spear was delayed by SA application and Lukaszewsaka and Kobyliñski, (2009) reported that SA treatment reduced chlorophyll degradation of detached leaves of Hippearstrum x chmielii during storage. In tomato fruit, Wang, et al. (2011) reported that postharvest treatment of SA accumulated total chlorophyll content and delayed the increase in lycopene and carotenoids contents. These works have supported our result that SA maintained the greenness of both lemon basil and holy basil during storage.

Figure 5. Superficial colours, L* (A), a* (B) and b* (C) values, of lemon basil (1) and holy basil (2)

treated with SA and stored at 8 ± 2 C for 4 days. Each bar represents the mean ± S.D. of four replicates.

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CONCLUSION Preharvest treatment of SA could alleviate chilling injury symptom and reduce the loss of

greenness in both lemon basil and holy basil during storage at 8 ± 2 C. We found that 10.0 mM SA application provided better result in alleviating chilling injury and maintaining greenness of both herbs than 1.0 mM SA; however, a tip burn was detected in both herbs. We suggest that preharvest SA treatment is an effective approach to maintain postharvest quality of lemon basil and holy basil during cold storage but a proper concentration of SA application need to be considered. ACKNOWLEDGEMENT

We are grateful to Faculty of Industrial Education, King Mongkut’s Institute of Technology Labkrabang for financial support this project. REFERENCES Asghari, M. and M.S. Aghdam. 2010. Impact of salicylic acid on post-harvest physiology of

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