This study aimed to investigate the firming effect of tawas, lime, and refrigeration on tomatoes. The exposure time and stage of ripeness (unripe, half ripe, ripe, and overripe) of the tomatoes used were varied. It was found that the effect of the four treatments (tawas-water solution, lime-water solution, refrigeration, and room temperature) on the firmness of tomatoes varied according to the degree of ripeness upon treatment and time of observation.
Consumers may not know it but the tomatoes they buy could have already passed through several treatments. Some vendors soak ripe tomatoes in tawas or alum solutions in order to maintain the firmness of the tomatoes. The amount of alum involved varies, but usually 1/4 kilo of alum is mixed with 30 liters of water. Soaking time runs for about half a day. Aside from tomatoes, vendors also soak wilting carrots, radish, sliced unripe jackfruit, and bean sprouts in tawas solution.
Foreign countries such as the United States have already recommended the use of lime as the better alternative to tawas to keep pickled fruits and vegetables crisp. Tawas could induce a bitter taste and has a level of toxicity. Aside from alum and lime, there is already a common middle-class household practice of refrigeration to preserve food. Thus, it had now become very interesting to find out the comparative effect and limitation of these three methods in keeping ripe tomatoes firm.
Definition of Terms
Tomato: the fruit of the plant Solanum lycopersicum, reclassified Lycopers icon lycopersicum, Lycopersicum esculentum, or kamatis in Filipino.
Tawas or alum: also known as aluminum potassium sulfate
Tawas-water solution: made by dissolving 1/4 teaspoon of tawas (0.6 grams) in 568 ml of water, resulting to a concentration of 0.105 percent
Lime: calcium hydroxide, also called apog
Lime-water solution: made by dissolving 1/8 cup of lime (13.25 grams) in 568 ml of water, resulting to a concentration of 2.33 percent
Firmness: the denseness or solidity of an object; a measure of the tomato's hardness as sensed by compressing or touching the tomato with the fingers; was rated from 1 to 4, with 4 being the firmest
Shelf life: the length of time a product can be stored without deterioration occurring