Thursday, December 24, 2015

Enhancing flavor of Tomatoes-Modified packing house practice

Tomato is one of the most liked vegetables, its use in many preparations and as a salad component being universal. In many diets and customary eating it is consumed almost every day across the world. Besides being a nutritious food, it also enriches flavors of many cooked foods and is a standard component of a good salad. No wonder the tomato paste industry is well established, catering to the needs of millions of consumers who find it is a convenient product with many application potential. A curious question many people find it difficult to answer is whether tomato is a fruit or a vegetable? As its sugar content is very low, unlike that in fruits, tomato is legally classified as a vegetable but still many people consider it as a fruit. What does a consumer expect from tomato? The crisp texture, attractively smooth appearance, intense color, juiciness and mild flavor. In contrast the tomato industry from growers to handlers, distributors and processors look for other more important qualities which include hard fruit resistant to damage during storage and transportation, longer shelf life and higher solid contents. Interestingly tomato production is concentrated in China and India, both together accounting for more than 30% of the global production of 170 million tons per year and therefore development of new varieties with better characteristics and yield is rather limited in these countries. In contrast advance countries like the Netherlands, Belgium, Ireland lead the productivity race with average productivity in the range of 430 to 480 tons per hectare. The path breaking research in evolving a genetically modified variety called FlarSavr took place in the US which was a dream come true for the industry though consumers never accepted this GM nineteen nineties. Almost 75% of the tomato produced is consumed in the fresh form which reflects the importance of delivering farm fresh tomatoes to the consumer with least time delay and minimum damage. According to a group of scientists working in the US commercially marketed tomato does not possess good flavor because of the practices followed by the industry which do not allow the metabolic system in the crop to function and generate optimum flavor. A new approach is being suggested to modify the handling practices that will enhance the flavor very significantly. Read further below:  

"The distinct flavor of tomatoes is due to a cocktail of chemicals produced by the fruits as they ripen, but, according to the team that includes the USDA, the Agricultural Research Service, and the University of Florida, conventional storage methods inhibit these flavors. If tomatoes seem more flavorsome when bought from a farm stand, that's because they're being sold in the ideal condition – fully ripe and immediately after picking. However, commercially grown tomatoes need to be shipped hundreds, if not thousands of miles to reach market along with delays in packing and unpacking. Shipping ripe tomatoes over any distances risks unacceptable levels of spoilage, so the tomatoes are picked green, treated with ethylene gas to induce ripening, and then chilled for shipping. According to team leader Jinhe Bai, this chilling prevents flavor compounds, such as 6-methyl-5-hepten-2-one, 2-methylbutanal, and 2-phenylethanol from forming and the tomatoes end up with a watery taste. To avoid this, the team added an extra step. Instead of sending Florida-grown green tomatoes straight on to chilling, the team plunged them into 125° F (52° C) water for five minutes, then cooled them to room temperature before a final chilling to between 41° and 55° F (5° and 13° C), which is the standard shipping temperature. Compared to a control group, the team found that the treated tomatoes had more smell and flavor, as well as higher levels of flavor compounds. According to Bai, this is due to the heat treatment regulating certain ripening enzymes and activating the production of a protein that makes the tomatoes tolerant of cell decay. "Chilling suppresses production of oxygen, nitrogen, and sulfur-containing heterocyclic compounds, ketones, alcohols and aldehydes, including 13 important aroma components of tomato flavor," says Bai."But hot water-treated fruit actually produced higher concentrations of these important aroma contributors, even with subsequent chilling." The team is currently testing the technique at various stages of ripeness to see how it affects flavor compound production. Bai says the next step is to determine which method is the most effective before offering it to food processing firms. In addition, they're trying alternatives to hot water, such as methyl salicylate (wintergreen oil), which is an anti-fungal fumigant, and 1-methylcyclopropene when the tomatoes are at the slightly riper green/pink stage to make the fruit more tolerant to cell decay when at higher storage temperatures."

Even to day why are people preferring to buy wine ripened tomato or directly from farm gates offering fresh ripened crops? Simply because these crops possess much better flavor compared to that bought from a supermarket. As explained by the authors of the above study, development of flavor from a cocktail of chemicals present in tomato depends on temperature. The commercial practice, heavily dependent on chilling to low temperatures for long distance transportation in the distribution chain to prevent physical damage, does not allow the inherent enzyme systems to act on the dormant precursors for conversion into the characteristic flavorful substances. The heat shock method developed by them is claimed to be able to "wake up" the metabolic activity which sets of the process of generating flavor substances. Since the method is very simple there should not be any logistical problem to incorporate this step into the currently practiced protocol. Hot water treatment has the additional advantage of sanitizing the product to some extent by killing some of the undesirable microbes. Way back in nineteen sixties a similar heat treatment was developed in India for mangoes for reducing microbial spoilage during the long process of ripening which takes more than a week. If the new findings are confirmed and accepted by the industry there could be a dramatic increase in the flavor quality of tomatoes consumed world over.


No comments: