Using Ethanol to Prevent the Decay of Table Grapes

In a BARD Fund-supported study, scientists have shown that treating table grapes with ethanol significanly slows down their decay process. Israeli grape growers are already using this method to keep their produce fresh.

Over the centuries, people have found a wide range of applications for ethanol, from an antiseptic and a poison antidote to its use in distilled spirits, perfumes, and paints. It has even joined the alternative energy era as a biofuel. In fact, most of the corn grown in the world today is geared toward producing ethanol for just that purpose. But can ethanol also be used as a pesticide, thereby increasing the fruit's shelf life?
A team of scientists supported by the BARD Fund has successfully developed a method that uses ethanol, either as vapor or in solution, to slow down the decay of stored table grapes. In fact, their extensive experiments have demonstrated that using ethanol is equally effective - and under certain conditions even more effective - than the most commonly employed decay-preventing method, which relies on the slow release of sulfur dioxide. The main benefits of the scientists' ethanol treatment are that it extends the grapes' shelf life by preventing decay and increases food safety by reducing the size of the E. coli population on the fruit, while leaving only negligible amounts of ethanol residues on the fruit.
Working to improve their ethanol treatment, the researchers discovered that it is possible to further protect the grapes from disease by treating them with a 30% ethanol solution in combination with a system that ensures that the fruit is kept in a non-humid environment. While this improved method was found to be safe for use, the scientists also demonstrated that it is likewise effective when the solution contains only 10% ethanol, a concentration permitted for usage by US regulation. To produce the same effect in the reduced ethanol treatment, the scientists either increased the temperature or introduced additives, such as sorbic acid, into the ethanol solution.
The main impediment to applying the researcher's ethanol method is a regulatory one. While many growers in California, for example, showed great interest in the ethanol treatment, a myriad of unique State taxes and regulatory issues associated with food grade ethanol use effectively barred its implementation.
Interestingly, the researchers found that their treatment was also effective when the fruit were treated prior to harvesting. The great advantage of the pre-harvesting option is that the treatment is more easily applied since there is no need to dry the fruit after dipping them in the ethanol solution.
The scientists believe that their ethanol treatment offers fruit growers a very practical method for preserving the freshness of ready-to-eat grapes and for protecting organic grape from pests, and it may also be applicable for other fruits. Indeed, many Israeli producers of table grapes for the local market are already applying the ethanol method to keep fresh their ready-to-eat produce.

The Core Group of Scientists:

  • Amnon Lichter, Volcani Center, Israel
  • Joseph L. Smilanick, USDA, ARS, USA