Moisture retention

A good compilation of the functions of fats in various food products is available (26). Some functions are quite subtle, eg, fats lend sheen, color, color development, and crystallinity. One of the principal roles is that of texture modification which includes viscosity, tenderness (shortening), control of ice crystals, elasticity, and flakiness, as in puff pastry. Fats also contribute to moisture retention, flavor in cultured dairy products, and heat transfer in deep fried foods. For the new technology of microwave cooking, fats assist in the distribution of the heating patterns of microwave cooking. 

The lambda type is nongelling, and functions as a thickner. Iota-carrageenan has been recommended (45) for use in formulating low fat ground beef due to its abihty to retain moisture, especially through a freeze—thaw cycle which is typical for ground beef patties. Oat bran and oat fiber can also be used to improve moisture retention and mouth feel. Modified starches can be used as binders to maintain juiciness and tenderness in low fat meat products. Maltodextrins (dextrose equivalent less than 20) may be used as binders up to 3.5% in finished meat products. Other carbohydrates such as konjac flour, alginate, microcrystalline cellulose, methylceUulose, and carboxymethylceUulose have also been used in low fat meat products (see CELLULOSE ETHERs). 

Food Applications. On the basis of intake, sucrose is the leading food additive (2). Its principal contribution to food is sweetness. However, it provides many other functionahties, eg, body, mouthfeel, texture, and moisture retention. Cereals and baked goods are the leading consumers of sucrose, followed closely by confectionery products (36). 

Vibrating-conveyor dryers are suitable for free-flowing solids containing mainly surface moisture. Retention is limited by conveying speeds which range from 0.02 to 0.12 m/s. Bed depth rarely exceeds 7 cm, although units are fabricated to carry 30- to 46-cm-deep beds these also employ plate and pipe coils suspended in the bed to provide additional heat-transfer area. Vibrating dryers are not suit le for fibrous materials which mat or for sticky sohds which may ball or adhere to the deck. 

Air pollutants may enter plant systems by either a primary or a secondary pathway. The primary pathway is analogous to human inhalation. Figure 8-2 shows the cross section of a leaf. Both of the outer surfaces are covered by a layer of epidermal cells, which help in moisture retention. Between the epidermal layers are the mesophyll cells—the spongy and palisade parenchyma. The leaf has a vascular bundle which carries water, minerals, and carbohydrates throughout the plant. Two important features shown in Fig. 8-2 are the openings in the epidermal layers called stomates, which are controlled by guard cells which can open and close, and air spaces in the interior of the leaf. 

Spent foundry green sand is of particular interest to soil blending companies that produce topsoil, because of its dark color, clay content, moisture retention, and consistency. A high sand content is required in topsoil, so spent foundry sand could be a major component. Spent sand reduces the... 

Juiciness. Juiciness of pork is associated with the amount of moisture present in the cooked product and the amount of IMF. Increase in ultimate pH of the pork is associated with increased moisture retention in the heated product. In contrast, low pH after slaughter, which gives rise to PSE pork, is closely related to low moisture content of cooked pork. Also the distribution... 

Soy proteins are used extensively in meat and meat products by the military, the school lunch program and consumers to save money. Their ultimate acceptability is equally dependent upon the nutritional, chemical, sensory and shelf life changes which occur when they are added. Soy proteins in meat products such as ground beef inhibit rancidity, improve tenderness, increase moisture retention, decrease cooking shrink, fat dispersion during cooking and have no important effect on microbiological condition. Concomittantly, inordinate amounts of added soy protein may cause the meat product to be too soft, exhibit an undesirable flavor and may lead to a decreased PER and a deficiency in B-vitamins and trace minerals. In emulsified meat products, soy protein effectively binds water but does not emulsify fat as well as salt soluble muscle protein. Prudent incorporation of plant proteins can result in an improvement of the quality of the meat product with inconsequential adverse effects. 

Rakosky ( ) reported that if a 25% shrink were obtained with an all meat product, the shrink in a meat product augmented with soy concentrate would be about 22.5%, or a 10% reduction in shrink. Use of textured soy rather than soy concentrate (Table IV) has been shown to reduce shrink in beef patties ( ,7 ). In a comparison of textured soy, soy concentrate and soy isolate, Berry et al. (7) found isolates gave the lowest cooked yields. In that study, cooking yields were directly related to the amount of dry soy in the ground beef-soy formulations. The greater quantity of soy (and correspondingly less water) in the textured soy flour formulation increased moisture retention and decreased total cooking loss. 

Amorphous Aluminosilicates. These occur in soils influenced by volcanic activity and are associated with very high moisture retention and anion fixation, and low to very high pH-dependent CEC. They may also bind organic matter tightly, protecting it against decomposition. Examples are allophane and imogolite. 

Brassicas need firm, moisture-retentive soil they do not thrive in dry conditions. In a crop rotation, this family best follows on from the nitrogen-fixing pea and bean family (see p.242). A green manure crop of winter vetch or clover provides leafy brassicas with all the nitrogen... 

Legumes thrive in well-drained but moisture-retentive soil that has been fed for a previous crop, such as potatoes. In a rotation they can... 

Bulky soil improvers spread over vegetable beds to condition and feed the soil applying water correctly at the roots of plants, rather than pouring it over the leaves the need for hoeing is reduced in these close-planted beds shallots growing through a mulch membrane for moisture retention and weed control. 

It comes as no surprise, perhaps, that fruit prefers deep, rich loam that is free-draining but moisture-retentive. You may not have these conditions at first, but much can be done to improve soil structure, open up heavy soil, and increase the water-holding capacity of light soil (see The Soil, pp.34-35). If starting with very poor soil, start to improve it a year in advance of planting fruit trees or bushes. 

Throughout the text we will relate polymer structure to the properties of the polymer. Polymer properties are related not only to the chemical nature of the polymer, but also to such factors as extent and distribution of crystallinity, distribution of polymer chain lengths, and nature and amount of additives, such as fillers, reinforcing agents, and plasticizers, to mention a few. These factors influence essentially all the polymeric properties to some extent including hardness, flammability, weatherability, chemical stability, biological response, comfort, flex life, moisture retention, appearance, dyeability, softening point, and electrical properties. 

Balasubramaniam, V. M., Chinnan, M. S., Mallikarjunan, R, Philips, R. D. (1997). The effect of edible film on oil uptake and moisture retention of deep-fat fried poultry product Journal of Food Process Engineerings 20(1), 17-29. 

Humectants hygroscopic substances incorporated in a product to promote retention of moisture, including moisture retention agents and antidusting agents. 

Protein additives also find use in numerous baked products. Soy flour increases the shelf life and freshness of breads, pancakes, waffles, and cakes through enhanced moisture retention (28, 40). Addition of soy flour to pancakes and doughnuts helps prevent excessive fat absorption during cooking (28). This phenomenon of decreased fat absorption is not well understood. 

A higher yield of cheese is obtained when homogenized milk is used for cheesemaking. This is due to increased fat and moisture retention of the curd. However, the fat in the whey cannot be recovered by centrifugal processes because of the failure of homogenized fat globules to cluster. 

Improved Comfort Properties. Wear comfort generally means cotton-like properties, The ability lo absorb moisture from the skin and ihe softness of cotton fabrics are considered to be the two key properties for comfort. The extremely line denier of cotton fibers accounts for its softness. Both properties can be achieved in acrylic fibers. Improved moisture retention can be achieved by incorporating hydrophilic comonomers that decrease ultimate fiher density, by modifying the fiber spinning process, ur by using after-treatments such as modified finishes. 

Figure B5.3.4 A comparison between moisture retention for a raw sample and the binding as measured by a sensory panel for fish muscle treated with different cations. Reprinted from Regenstein (1984) with permission from the American Meat Science Association and Zwika Weinberg (Volcani Center, Agricultural Research Organization, Israel).

Expressible moisture and water uptake ability measure different properties. Figure B5.3.2 shows the very different cation and anion dependencies of these methods using fish samples. Figure B5.3.3 shows that the pH profiles are also different. It is also apparent that WUA is often >100%, while expressible moisture must, of necessity, be <100%. Figure B5.3.4 shows an example where expressible moisture was actually correlated with a separate and independent functional measurement. In this case, the binding of cooked fish muscle as determined by a subjective sensory panel pulling samples of fish apparently paralleled the moisture retention of the raw fish (moisture retention = 1 - expressible moisture). Ideally, functional properties should show such correlations with other properties of interest in food systems. 

Cui and Mazza (1996) reported that neutral polysaccharides have a larger molecular size than acidic polysaccharides and flaxseed gum showed superior moisture retention properties compared to carboxymethylcellulose, Arabic, guar, and xanthan gums. Acidic polysaccharides show more shear... 

---