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- All Dried Up
- Dehydration workshop shows how to add value to fruits, vegetables and herbs
- By Dr. John Roberts
Cornell University
- From being consumed separately or in snacks such as trail mixes to ingredients in baked goods and cereals, dehydrated fruits have been an important and increasing product in the marketplace. Being one of the oldest processing techniques, dehydration has continued to be a very attractive method in preserving perishable produce while at the same time producing a delicious and nutritious product.
With improved techniques and advanced and cheaper equipment, drying foods is easier than ever. A workshop entitled “Fruit, Vegetable and Herb Dehydration” was offered on April 10 at Cornell University’s Department of Food Science located at the New York State Agricultural Experiment Station in Geneva, N.Y. Dr. John Roberts, assistant professor of food engineering at Cornell, organized the workshop to focus on small-scale production.
The interest in dehydrated foods was reflected in the 29 individuals who attended this one-day workshop to learn about proper techniques in producing high quality dehydrated products. The morning was dedicated to lectures covering dehydration basics, shelf life and regulations of dehydrated foods, microbiology and sanitation practices, and packaging. The afternoon was dedicated to demonstrations of the most popular dehydrators on the market, sampling of many dehydrated fruits, vegetables and herbs having various pre-treatments, and open discussion relating to potential and hurdles of starting and developing dehydrated products. This “show and tell/hands-on” session was very well received by all who attended, and many stated that they appreciated the first-hand experience of both how each dehydrator operates as well as what products and pre-treatments work the best for various fruits, vegetables and herbs.
The workshop started with an overview of dehydration given by Roberts. He discussed the several stages of moisture loss during dehydration and the factors that effect moisture loss and product quality at each stage. Roberts also provided important pretreatment techniques specific for fruits and vegetables. Blueberries, for instance, must be boiled for a few minutes to “crack” the skins and allow the internal moisture to escape. Cherries, because they are pitted, and strawberries, because they are topped and cut in half, are small fruits that do not have to be boiled before dehydration. Some light colored fruits, such as apples, have to be dipped in an ascorbic acid solution prior to dehydration to minimize browning.
Roberts ended his talk by describing proper methods to determine if sufficient moisture has been removed. He pointed out that due to the concentration of sugars and acids, fruits do not need to be dried to as low a moisture content as vegetables are required to achieve.
The second talk was on water activity and regulations regarding dehydrated foods, and was presented by Dr. Olga Padilla-Zakour, assistant professor of food processing at Cornell and director of the New York State Food Venture Center. She further explained how removing enough available water in the food suppresses both growth of spoilage organisms and deteriorative reactions to extend the shelf life. Padilla-Zakour also covered the regulations regarding food manufacturing at home and in small kitchens for commercial sale, inspections, and proper labeling.
Dr. Randy Worobo, assistant professor of food microbiology, presented microbiology and sanitation. He first covered the basics of food microbiology, including spoilage and pathogenic microorganisms and how these microorganisms survive and grow. Worobo further explained how pathogens enter the food supply and covered ways to prevent contamination through good hygienic and sanitation practices. Worobo also pointed out that raw foods should be processed, either frozen or dehydrated in this case, as quickly after harvest as possible.
A summary of the history of packaging of food, as well as outlining the purposes of packaging and guidelines on how to choose the best package for your dehydrated product was given by Dr. Joe Hotchkiss, professor and chair of the Department of Food Science, Cornell University, Ithaca. Hotchkiss provided an entertaining presentation with pictures of well-recognized food packages and also brought several foods representing the various types of packaging. He emphasized that it is a waste of money to use a package that maintains its barrier properties long after the product maintains its quality. Hotchkiss concluded his talk with the message that one must take the time and effort to “shop around for the best package to suit their needs.”
A very interesting presentation was given by Matthias Resen, of Healing Spirits Herb Farm and Education Center, on solar drying in the Northeast. Resen showed slides of his solar dehydration facility located in upstate New York where he dries various herbs.
The last two hours of the workshop were spent in the pilot plant of the Department of Food Science and Technology, where Roberts had three dehydrators operating and many products displayed for the attendees to sample. Of particular interest where the dehydrated berries, which are widely produced in upstate New York. The attendees sampled dehydrated strawberries and blueberries from fresh and from frozen storage, as well as cherries from frozen storage and blackberries from fresh.
The dehydrated fruit from frozen storage resulted in a very nice dehydrated product, but Roberts was quick to point out that the fruit has to be in excellent quality before frozen storage. Also, the attendees were surprised to realize that many of the dehydrated berries were improved by first osmotically drying the fruit. This pre-treatment step involves submerging the fruit in a saturated sugar solution overnight. By osmosis, moisture within the fruit migrates out to the solution and sugars migrate into the fruit. The result is improved flavor and texture of the dehydrated fruit.
Fruits that would benefit from such a pre-treatment are those that are tart, such as tart cherries and early picked strawberries and blueberries, as well as those berries that would normally break down significantly during dehydration, such as raspberries and blackberries. Other dehydrated fruits that were on display were apples, peaches, and bananas, with and without an anti-browning pre-treatment (ascorbic acid solution). Since most of the attendees have their own farms and are quite busy during the picking season, they were happy to hear and taste that the fruit can be frozen during the picking season and then thawed and dehydrated later in the fall or winter.
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