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Recent Developments in Intermediate Moisture Foods

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Recent Developments in Intermediate Moisture Foods 484 Journal ofFood Protection. Vol. 45, No.5, Pages 484-491 (Aprill982) Copyright International Association of Milk, Food, and Environmental Sanitarians Recent Developments in Intermediate Moisture Foods L. E. ERICKSON Department ofChemical Engineering, Kansas State University, Manhattan, Kansas 66506 (Received for publication March 9, 1981) Downloaded from http://meridian.allenpress.com/jfp/article-pdf/45/5/484/1653902/0362-028x-45_5_484.pdf by guest on 27 September 2021 ABSTRACT HISTORY OF INTERMEDIATE MOISTURE FOODS The science and technology of intermediate moisture foods Modification of foods to increase shelf-life has been has advanced during the last 25 years. Developments during going on for many years. Food preservation based on the this period are reviewed. Knowledge of the relationship of water lowering of water activity to a level at which microbial activity and food degradation has advanced considerably growth is prevented or reduced has been going on since during this period. Many new intermediate moisture foods have sun-dried foods and salted foods were first developed. been developed. Several methods have been developed to alter Referen~es to sun drying can be found in the Bible, the water activity offoods. ancient Egyptian hieroglyphics and in the journals of Marco Polo (17). Salting and sugaring of foods also have a long history. However, an understanding of the Intermediate moisture foods are foods with moisture importance of water activity in food preservation was content between dry foods which can be stored at room advanced significantly in 1957 with the work of Scott temperatures and moist foods which need to be frozen, (28). lt is clear that water activity and modification of refrigerated, canned or preserved by some other water activity have become central considerations in the mechanism. A precise definition of intermediate development of intermediate moisture foods (4,6, 7,8,13, moisture foods based on water content or water activity 15,17,20,24,28,30). has not evolved. According to Karel (15) traditional Examples of traditional intermediate moisture foods intermediate moisture feeds have moisture contents include dried fruits such as prunes; products to which between 10 and 40o/o and water activities from 0.65 to sugar has been added, such as candies, marshmallows, 0.90. Corry (7) has pointed out that the water activity jams and pie fillings; dried products with salt and sugar, range of intermediate moisture foods differs from author added such as hams, and bakery products, such as fruit to author with values ranging from 0.70- 0.85 (4), 0.60 - cakes. Table 1 shows the water activity of some 0.85 (24), 0.70 - 0.90 (13), and 0.60 - 0.90 (6). Corry (7) traditional intermediate moisture foods (15). points out that a range of water activities from 0.70- 0.90 for intermediate moisture foods is reasonable because TABLE L Water activity of selected traditional intermediate moisture foods (15). foods with water activities below 0.7 are stable for considerable lengths of time with respect to microbial Food Water activity spoilage and can be classified as "dry", and foods with a Liverwurst 0.96 water activity of0.90 or below do not support growth and Salami 0.82-0.85 toxin production by most bacteria. 'Landjiiger' sausage 0.79 Kaplow (12) defines intermediate moisture foods as, Dried fruits 0.72-0.80 "An Intermediate Moisture Food is one which can be Jams and jellies 0.82-0.94 eaten as is, without rehydration, and yet is shelf-stable Honey 0.75 of commercial 0.65-0.71 without refrigeration or thermal processing" (8). In the development of intermediate moisture foods, Robson (26) has pointed out that reduced spoilage, improved safety. There are three important recent developments with increased shelf-life and retention of soft moist texture are respect to intermediate moisture food products. Develop­ important considerations. Reduction of water activity is ment of intermediate moisture pet foods has been most frequently necessary to develop an intermediate moisture successful (5,8). A large fraction of the current market is food which is shelf-stable without refrigeration. ftlled with these products. The development of extrusion JOURNAL OF FOOD PROTECTION. VOL. 45, APRIL 1982 INTERMEDIATE MOISTURE FOODS 485 cooking to produce most of these pet food products is TABLE 4. Characteristics of some recently developed inter- also significant (10). The second development in food mediate (15). products includes intermediate moisture foods for Characteristic IMFCatfish IMF Coconut milk IMF Cheese defense, space flights, explorers and others on extended 0.8 0.75-0.8 0.82 missions (11 ,15,26). The third is development of new ~ Water (o/o) 26.6 30-35 "-'25 intermediate moisture foods for the general public (8). pH 6.4 7 5.2 Table 2 shows the formula for a soft moist pet food Additives K-sorbate 0.1 o/osorbic acid K-sorbate (11). Table 3 shows the formula for one of several new P.G.a P.G. intermediate moisture foods developed by Swift and Sorbitol NaCl Company for the U.S. Air Force (11). Tables 4 and 5 Sucrose show some of the important characteristics of some other NaC1 intermediate moisture products developed for the ap .G. Propylene glycol. defense and space programs (15). Table 6 shows some of the intermediate moisture foods which were found in the Downloaded from http://meridian.allenpress.com/jfp/article-pdf/45/5/484/1653902/0362-028x-45_5_484.pdf by guest on 27 September 2021 supermarket (8). TABLE 5. Analysis of example intermediate moisture foods (15). TABLE 2. A typical soft, moist (intermediate moisture) pet Water Average food formula (ll)a. Cubes content percent pH Water Ingredients Parts by weight (%) salt activity Chopped meat by-products (tripe, udders, Roast beef 22.2 3.0 5.75 0.79 cheek trimmings, tongue trimmings, Barbecue beef 16.2 2.7 5.05 0.66 gullets, etc.) 32.0 Roast pork 22.4 3.6 5.70 0.74 Defatted soy flakes 31.0 Barbecue chicken 19.7 4.0 5.20 0.70 Sucrose 21.7 Chicken a Ia King 14.9 3.6 5.90 0.61 Flaked soy bean hulls 3.0 Beef stew 17.3 3.7 5.80 0.65 Dicalcium phosphate 3.0 Corned beef 16.2 5.4 5.85 0.62 Dried non-fat milk solids 2.5 Chili with beans 13.9 2.6 5.65 0.79 Propylene glycol 2.0 Sausage 24.2 4.5 4.90 0.78 Bleachable-fancy tallow 1.0 Ham 19.9 4.5 5.90 0.72 Mono- and diglycerides 1.0 Sodium chloride 1.0 Potassium sorbate 0.3 TABLE 6. Intermediate moisture food products noted on FD&Creddye 0.006 supermarket tour (8). Garlic 0.2 Vitamin and mineral premix 0.06 Type Name Manufacturer aFrom U.S. Patent 3,202,519 (1965). Historical Jams, jellies Sausage Some cheese TABLE 3. Formula of ready-to-eat intermediate moisture "Dried" fruit ham cubesa (11). Marshmallows Many Ingredients "Toby weight Honey Country hams Ham, cooked, ground, freeze dried 45.00 Jerkey Water, distilled 10.000 Salted fish Water as steam 12.4215 Maple syrup Non-dairy coffee whitener 6.30 Glycerol 6.00 Traditional Pop-Tarts Kellogs Pregelatinized starch 5.50 Slim Jims General Mills Gelatin (175 bloom) 5.00 Hostess pies ITT Continental Sorbitol, dry 3.00 Ready to spread General Mills Sucrose 2.20 frosting Hydrolyzed vegetable protein, Ham 2.00 Cereal 1.50 Semi-Traditional Breakfast squares General Mills Monosodium glutamate 0.46 Pie sticks General Mills Liquid smoke (Char-Oil) 0.35 Pizza crust Fairmont Foods Sorbic acid 0.20 Ascorbic acid 0.045 Novel Pet foods Ribotide 0.02 Infusion cooked Citric acid 0.0035 Extrusion-particles Many Total 100.0000 Extrusion-patties a Developed by Swift & Company for U.S. Air Force. Food sticks Pillsbury JOURNAL OF FOOD PROTECTION. VOL. 45, APRIL 1982 486 ERICKSON TECHNOLOGY OF INTERMEDIATE MOISTURE FOODS Humectants may be added to develop intermediate moisture foods with more favorable water sorption The technology of intermediate moisture foods may be isotherms. Salt is an example of an excellent humectant. divided into several parts. The food science associated Addition of salt to the food reduces water activity with with characterization of these foods is one aspect. The only a small reduction of moisture content; that is, the stability of intermediate moisture foods under various curve in Fig. 1 is shifted to the left by adding humectants. storage conditions and the associated chemical and In characterizing intermediate moisture foods, it is microbial processes of degradation are another part. The important to realize that water activity and water technology of developing a new intermediate moisture sorption isotherms are part of the science of equilibrium food, including the processing and selection of thermodynamics. The adsorption and desorption iso­ ingredients, is another consideration. The nutritional therms frequently do not agree with each other and aspects ofthese foods is also important. hysteresis is observed. Moreover, repeated experiments Characterization may reveal a slowly shifting water sorption isotherm (9). An important method used to describe a food product The shifting and hysteresis occur because equilibrium Downloaded from http://meridian.allenpress.com/jfp/article-pdf/45/5/484/1653902/0362-028x-45_5_484.pdf by guest on 27 September 2021 is a list of the ingredients, including the moisture content conditions are not attained. In spite of these problems, and amount of each ingredient. Since microbial water activity is a useful concept for characterizing degradation offood products is related to water activity, intermediate moisture foods. this is an important characteristic of intermediate Water activity is the ratio of the fugacity, f, at the moisture foods.
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