1. Hot Water Treatment of Tomatoes
Hi, my name is Ploy Kurdmongkoltham. My postharvest project is using hot water to reduce decay during postharvest wash of tomatoes.
Ploy Kurdmongkoltham

2. Introduction Postharvest loss is a worldwide problem
FAO estimated 1.3 billion tons of food are wasted annually through (Gustavasson et al )
Decay is one of the major factors in food loss
Mismanaged handling and storage step can increase decay incidence
Decay can occur by:
Product mishandling
Inadequate storage
Internalized pathogen from field
Postharvest loss is a worldwide problem for both developed and developing countries. 1.3 billion tons of food are wasted annually. Loss can happen at farm, retail, and consumer level. Food loss caused by decaying organisms is one of the major factors in food loss.
There are multiple stages between farm to consumer supply chain, however proper handling and storage of commodity is an important factor in reducing decay incidence. Decay can be caused by mishandling of products which introduces pathogens, lack of adequate storage facility, or pathogen that is already present in the commodity during preharvest and produces symptoms during postharvest.

3. Objective Chlorine solution is generally used in dump tanks
pH must be maintained
Organic matter accumulation reduce free chlorine (Zhou et al. 2013)
Formation of trihalomethanes
Chemical-free treatment can be a better alternative
Determine whether hot water treatment can reduce decay incidence in tomatoes
While chlorine solution is normally used for pathogen reduction in dump tanks for tomatoes, there are many factors to be considered for maintaining its effectiveness.
pH must be kept between to keep the active ingredient (HOCl) at a high concentration.
Organic matter that will naturally accumulate in the dump tank can reduce free chlorine in the tank
Trihalomethanes can form using chlorine which is a health concern
Finding an alternative to chlorine treatment may be beneficial for the future.
Hot water treatments are used on seeds for disease management. It is also used on mangoes and other stone fruits during postharvest. Therefore, the objective of the project is to determine whether hot water treatment can reduce decay incidence in tomatoes.
NaOCl + H2O Na+ + HOCl + OH–

4. Materials 24 ripe tomatoes Soft rot inoculum Erwinia spp. Nail
Thermometer
Hot water bath (52C )
Ambient water tub (25C )
Materials used in the experiment included 24 ripe tomatoes brought from grocery store, inoculum from tomato that had soft rot symptoms, nail for wounding the tomatoes, thermometer to measure water temperatures, hot water bath, and a tub filled with ambient water.

5. Four Treatments HOT WATER 6 wounded tomatoes, no inoculum
6 wounded tomatoes, with inoculum
AMBIENT WATER
There are four treatments:
Non-inoculated tomatoes in hot water
Inoculated tomatoes in hot water
Non-inoculated tomatoes in ambient water
Inoculated tomatoes in ambient water

6. Procedure Inoculation w/ soft rot No Inoculation Hot water:
52C for 5 mins
Inoculation w/ soft rot
Ambient water: 25C for 5 mins
Stored at 20C for 13 days
Hot water:
52C for 5 mins
No Inoculation
Tomatoes were sterilized with 85% ethanol for 1 min and dried
24 tomatoes were fully dipped into 85% ethanol for 1 minute and dried under fan for 30 minutes. All tomatoes were wounded with sterilized nail. The nail was re-sterilized after each stab with alcohol and flame. The wound site was circled with marker. 12 tomatoes were inoculated with a drop soft rot bacteria at wound site and the other 12 tomatoes were not inoculated.
For non-inoculated tomatoes, 6 tomatoes were placed in hot water treatment at 52C for 5 minutes and other 6 tomatoes were placed in ambient water treatment at 25C for 5 minutes. They were taken out and placed in separate plastic bins lined with wet paper towels.
For inoculated tomatoes, 6 were placed in hot water treatment at 52C for 5 minutes and other 6 tomatoes were placed in ambient water treatment at 25C for 5 minutes. They were taken out and placed in separate plastic bins lined with wet paper towels.
The bins were stored in 20C for 13 days. Soft rot symptoms were observed every 2 days.
*The temperature for hot water was based from Dr. Francisco Ernesto Loayza Davila dissertation on Application of Heat Stress and Their Effect on the Antioxidant Composition of Fresh Tomatoes.
Tomatoes were wounded with sterilized nail
Ambient water
Ambient water: 25C for 5 mins

7. Results – Hot Water TIME No Inoculum Inoculum
2 out of 6 showed decay at wound site
4 out of 6 showed decay at wound site, but progress at slow rate
The results shown here are from the first reading to the last reading of each treatment. The tomatoes were observed at wound site for decay and tissue break-down.
For non-inoculated tomatoes in hot water, 2 out of 6 tomatoes showed decay at wound site. There were tissue break-down observed in one of the tomatoes. There were yellow liquid exuding from the wound sites.
For inoculated tomatoes in hot water, 4 out of 6 tomatoes showed decay at wound site, but the progression of decay was slow. Wound site increase in size, but there was no complete tissue break-down.
Inoculum
TIME

8. Results – Ambient Water
No Inoculum
1 out of 6 showed decay at wound site
3 out of 6 showed decay at wound site, but one progressed at faster rate
For non-inoculated tomatoes in ambient water, 1 out of 6 tomatoes showed decay at wound site with complete tissue break-down and liquid exuding from wound site.
For inoculated tomatoes in ambient water, 3 out of 6 tomatoes showed decay at wound site. One progressed decay at a fast rate (circled) when compared to hot water treatment, and the tomato showed tissue break-down.
Inoculum
TIME

9. Conclusion Decay incidences were recorded for all treatments
Hot water treatment did not prevent decay, but showed a slower progression of rot
Some tomatoes in non-inoculated treatments showed decay symptoms.
Possibly due to pathogen already internalized in tomato
Decay incidences were observed for all treatments. Hot water treatment did not prevent decay, but it showed a slower progression of rot at wound site. Tomatoes in the non-inoculated treatments showed decay symptoms as well, but this may be due to pathogen already internalized in the tomato prior to the experiment.

10. Literature
Bartz, J Class notes: Controlling postharvest diseases. HOS 5085C Gustavsson, J., C. Cederberg, U. Sonesson, R. van Otterdijk, A. Meybeck Global Food Losses and Food Waste: Extent Causes and Prevention. Rome, Food and Agriculture Organization (FAO) of the United Nations. Loaya-Davila, F.E Application of heat stress and their effect on the antioxidant composition of fresh tomatoes. Dissertation. University of Florida. Zhou, B., Y. Lou, E. Turner, Q. Wang, K.R. Schneider Evaluation of current industry practices for maintaining tomato dump tank water quality during packinghouse operations.