Pengaruh Perlakuan Heat Shock dan Pelapisan Aloe Vera pada Gejala Chilling Injury untuk Tomat (Lycopersicon Asculantum Mill.)

This research was undertaken to determine the effect of length in heat shock and edible coating as prestorage treatment on Chilling Injury (CI) symptom reflected by ion leakage induced and quality properties in tomato (Lycopersicon asculantum Mill.). Heat Shock Treatment (HST) was conducted at three different levels of length, which were, 20, 40 and 60 min. Edible coating was conducted using aloe vera gel. The result showed that HST and Aloe Vera Coating (AVC) were more effective to reduce CI symptom at lower chilling storage. Prolong exposure to heated water may delay climacteric peak. The length of heat shock; AVC treatment and low temperature storage significantly affected the tomato quality parameter but not significantly different for each treatment except weight loss. HST for 20 min at ambient temperature was significantly different to other treatment. Keywords: ion leakage, chilling injury, climacteric, shelf-life Diterima: 2 Desember 2009; Disetujui: 22 Maret 2010


Introduction
It is well known that storage kat below room temperature and above freeze temperature may extend horticultural crops shelf life. Meanwhile, some physiological disorders were occurred in a number of horticultural crops due to its temperature condition. Failure to ripen, skin lesions and susceptibility to decay are typical symptoms of Chilling Injury (CI) (Lurie et al. 1997). Symptoms of CI include increased membrane permeability and a resultant increase in leakage of cellular constituents (Murata 1990;Sharom et al. 1994in Saltveit 2005. The rate of ion leakage from excised tissue into an isotonic aqueous solution is a useful measure of the severity of chilling-induced increase in membrane permeability (King and Ludford 1983;Saltveit 2002in Saltveit 2005. Ion leakage has been used as an indicator of damage to the plasma membrane and CI (Marangoni, Palma and Stanley 1996). The extent of injury depends on the environ ment to which the tissue was previously exposed, the type of tissue (e.g. meristematic, vegetative, root, stem, leaf and unripe or ripe fruit), temperature and length of exposure, and post-chilling conditions (Saltveit 2005). This phenomenon is especially important in postharvest handling and storage, as the use of low temperature is the most effective method to extend storage life of many products.
The application of a moderate heat treatment deeply modified postharvest metabolism which delay fruit ripening and decrease fruit decay (Vicente et al. 2006). A short-term treatment in water at 39-45 o C appears to be an effective, inexpensive and environmentally safe method that reduces CI and decay (McDonald et al. 1999). In recent years, there have been several reports on the use of pre-storage heat treatments to reduce CI in horticultural crops exposed to low temperatures.
Aloe vera gel can be used as an edible coating to prolong quality and safety of fruits and vegetables. Maintaining sweet cherry quality using Aloe Vera Coating (AVC) was effective to reduce weight loss and lower respiration rate during postharvest storage (Romero et al. 2006). Polysaccharide edible coating has been widely applied as a means of permeable membrane to extend self life by reduce respiration rate. Aloe vera consists of polysaccharide functional component which enable to delay fresh horticulture deterioration by controling water losses and prevent exchange of chemical component which dissolved in water.

Effect of Heat Shock Treatment and Aloe Vera Coating on Chilling Injury Symptom in Tomato (Lycopersicon asculantum Mill.)
Research data reported in this paper were undertaken to determine the effect of length in Heat Shock Treatment (HST) and AVC treatment to CI symptom reflected by ion leakage induced and quality properties in tomato (Lycopersicon asculantum Mill.).

Plant Material
Mature green tomatoes were harvested from grower in Goalpara, Sukabumi in the morning and transported one day after harvested to the laboratory for four hours where the fruits were placed at ambient temperature. Upon arrival at the laboratory, fruits were threatened by HST and AVC.

Application of Heat Shock Treatments and Aloe Vera Coating
HST for mature green tomatoes was applied by soaking fruits into single hot water maintained at temperature ranging from 39 o C to 48 o C for 15 min to 6 h (McDonald et al. 1999;Saltveit 2005;Baloch et al. 2006). Tomato was trimmed by 1 cm x 1 cm x 1 cm and soaked into 40 ml aqueous solution maintained at 42 o C for 20 min, 40 min and 60 min.
AVC was performed by immersing for 5 min in a solution of aloe vera diluted 1:3 with distilled water at 20 o C and then being air-dried (Romero et al. 2006). Fruits were coated by edible aloe vera gel where fruits were immersed into 200 ppm chlorine solvent for 30 min.

Application of Low Storage
After exposed into 42 o C and coated using aloe vera, in separate treatments, fruits were stored at 5 o C and 10 o C for 20 days. Fruits with non HST and AVC then stored at ambient temperature which were performed for control. Every 1 d storage, each sample was removed in to ambient temperature for 5 h to measure total electrical conductivity and quality properties.

Measurement of Chilling Injury and Quality Properties
CI was determined by increasing of ion leakage during storage on chilled temperature which was reflected by total electrical conductivity. Periodically, the conductivity of the solution was measured every 20 min for 300 min at ambient temperature using electrical conductivity meter (D-24 HORIBA). In the end, sample was gently shaken using blender for 2 min to dissolve ion into aqueous solution to measure total electrical conductivity. During storage, respiration rate; weight loss; Solid Soluble Content (SSC); firmness and color were measured. Fruit firmness was determined using rheometer CR-300, maximum load 2 kg, vertical pericarp surface 10 mm and pin diameter 5 mm. Weight loss was measured using digital scale to determine the initial and the final weight in each day. SSC was measured using ATAGO refractometer PR-201. Color was measured using chromameter.

Statistical Analysis
Statistical analysis was applied in order to see the significance level between treatments include HST and AVC; and also temperature storage to quality parameters include weight loss, firmness and SSC at the same maximum day of sample shelf life in each treatments. Each measurement was repeated three times. Variance analysis using Duncan Multiple Range Test (DMRT) with SAS was applied to perform statistical analysis.

Ion Leakage and Respiration Rate
Both treatments, HST and AVC, reflected lower ion leakage changes at storage of 5 o C than at 10 o C. Ion leakage from mature green tomatoes gradually decreased following storage at 5 o C, but it increased drastically at 10 o C storage (Fig. 1). On day of 19, there was significant different of total conductivity between storage at 5 o C and 10 o C. Thus showed that treatments using HST and AVC were more effective to prevent CI on lower temperature storage, which was 5 o C. Marangoni et al. (1996) reported that ion leakage increased drastically only after transfer to higher temperatures. Tomatoes chilled for 20 days at 5°C did not show increases in ion leakage. Damage to cells and tissues of tomato fruits occurred primarily Figure 1. Total conductivity for heat shock treatment and aloe vera coating at: a) 5 o C and b) 10 o C during exposure to the chilling temperature, while development of injury symptoms mainly occurred upon removal from chilling to a warm, non-chilling temperature (Jing et al. 2009). Both storage at 5 o C and 10 o C, HST for 20 min produced the lowest total conductivity after removal. A short heat treatment on strawberry fruit quality and shelf-life could be partly due to the higher protection against oxidative molecules generated during fruit senescence or pathogen attack (Vicente et al. 2006).
In each treatment during storage, HST and AVC, greater temperature storage increased respiration rate and longer HST period delayed climacteric peak (Fig. 2). Climacteric peak on storage temperature was conditioned at 5 o C on HST 20 min; 40 min and 60 min; AVC; control occurred at day 4, day 5, day 7, day 6, day 5 respectively. Where the storage conditioned at 10 o C, climacteric peak occurred at day 3, day 2, day 4, day 5, day 3, respectively. Respiration rates represented by production rate of CO 2 of tomato treated at 5 o C were considerably lower than those treated by 10 o C and ambient temperature. Heat water treatment increased respiration and ethylene evolution (McDonald et al 1999).

Quality Properties
As mentioned above, statistical analysis was conducted at the same maximum day in each treatment, obtained at the 5 th day. Table 1 represents DMRT value for each treatment. Treatments and temperature storage were significantly affected the weight loss percentage at day 5. HST for 20 min at ambient temperature was higher and significantly different from other treatment. Higher temperature increased percentage of weight loss (data not shown). Treatment with AVC showed no significantly different value.
At the early storage period, SSC started to increase then decreased (Fig. 3). Thus showed fruit climacteric phase character. Each treatment involved HST, AVC and low temperature storage significantly affected SSC at day 5 but there were no significantly different for each treatment. Similar Table 1. Duncan Multiple Range Test (DMRT) for each treatment Figure 2. Respiration rate (ml.kg -1 .h -1 ) of tomato under HST and AVC treatments before storage at: a) 5 o C and b) 10 o C to SSC, firmness was either showed that each treatment was significantly affected but there were no significantly different for each treatment. In the end of storage, fruits with unheated and uncoated treatments had the lowest value for both SSC and firmness. CI is related with the damage of cell structure under chilling stress. Ultra structural membranes were well prevented from chilling damage by hot water treatment (Jing et al. 2009 respectively. In the early storage period, a* value increased raised to red while b* value decreased raised to dark yellow. Some symptoms such as excessive water loss and skin lesion can develop during prolonged storage at chilling temperatures (Jing et al. 2009). The mechanisms by which pre-storage heat treatment reduces CI are still not very clear. Protective treatments such as temperature conditioning and heat shocks that are applied before chilling are thought to make tissue more resistant to the physiological damage that occurs during chilling. Heat treatment induces the synthesis of heat-shock protein, which is thought to act as chaperones that could be responsible for protein folding, assembly, translocation and degradation in many normal cellular processes, as well as assisting in protein refolding under stress conditions (Wang et al. 2004in Jing et al. 2009).

Conclusion
Hot water treatment and aloe vera coating were more effective to reduce chilling injury symptom at lower chilling storage. Prolong exposure to heated water may delay climacteric peak. Extended period of heat shock treatment; aloe vera coating and low temperature storage significantly affected the tomato quality parameter but not significantly different for each treatment except weight loss. Heat shock treatment for 20 min at ambient temperature was significantly different to other treatment.