A PPLICATIONS AS F AT M IMETICS ,S TABILIZERS , AND T HICKENING A GENTS

1.8.2 A PPLICATIONS AS F AT M IMETICS ,S TABILIZERS , AND T HICKENING A GENTS

Many cereal fractions enriched in β-glucans or β-glucan concentrates with fat replacement potential have been developed and described in numerous studies and have also been patented. The development of a weak gel network structure by cereal β-glucans with certain structural characteristics and under certain conditions 17,18,21 is a desirable attribute in water-continuous, low-fat spreads. Moreover, cereal β-glu- cans show potential as fat replacers due to their highly viscous nature and water- binding, foaming, and emulsion-stabilizing capabilities. 199,200 Kontogiorgos et al. 200 investigated the effects of pure barley and oat β-glucans on rheological and creaming behavior of concentrated egg yolk-stabilized model emulsions (salad dressing

model). The high molecular weight β-glucans (apparent M w ~ 110 × 10 3 ) stabilized the oil-in-water (o/w) emulsions mainly by increasing the viscosity of the continuous phase, while the low molecular weight β-glucans (apparent peak M w ~ 40 × 10 3 ) influenced emulsion stability through network formation in the continuous phase. The comparison of egg yolk with the Tween 20-stabilized emulsions demonstrated that the egg yolk acts synergistically with β-glucans, offering protection from cream- ing even at low oil volume fractions.

Oatrim, a product from enzymatically hydrolyzed oat flour or bran, containing oat β-glucans (1 to 10% db) and amylodextrins, has been proposed by Inglett 24,201–203

as a fat mimetic in a gel form substituting for shortening in oatmeal–raisin cookies. This product is being used experimentally in various reduced-fat, low-calorie for- mulations and soluble fiber-enriched foods, such as meats, muffins, cakes, oat fiber milk, frozen desserts, yogurt, sour cream, cheese spreads, salad dressings, sauces, gravies, soups, mayonnaise, margarine, snacks, breakfast cereals, and candy prod- ucts. Jenking and Wild 204 proposed a cereal or grain enzymic hydrolysate, which could be used in combination with a hydrocolloid (carrageenan or blend xan- than/locust bean gum) as a fat mimetic in low-fat meat products (frankfurters, beef and pork sausage patties). The fortified products were characterized by organoleptic

Cereal β -Glucans: Structures, Physical Properties, and Physiological Functions 45

features comparable to the full fat product, good cooking yields, and the benefit of β-glucans; thermoirreversible gels useful for providing fat mimetic attributes can also be prepared according to this method. Inglett also described the production of dietary fiber zero-calorie gels (Z-Trim gels) from corn, wheat bran, oat hulls, and a variety of other insoluble fibers (soybean, rice, peas) by a multistage alkaline–high- shear process. 205 The combination of Z-Trim with other hydrocolloids, including Oatrim, provided different options of generating food textures in low-calorie snacks, hamburger and other meat products, cheese, and some baked foods. In a later study, by a heat-shearing treatment of oat and barley substrates, Inglett 206 produced hydro- colloidal formulations, which are rich in soluble dietary fiber, principally β-glucan (1 to 15%). Dispersions of these materials are smooth in texture and display the properties of a dairy cream, coconut cream, fat imitation, or substitute for shortening. Moreover, the incorporation of steamed or wet cooked kibbles or flakes with elevated levels of β-glucan obtained from pearled barley has been proposed in meat loaf as

a fat mimetic and in sauces (gravies, tomato sauces) and soups as a thickener; 207 the addition of barley kibbles in burgers at concentrations from 5 to 20% gave a juicy and tasty patty with reduced animal fat content. Reduced-fat (12% w/w) breakfast sausages formulated with barley β-glucan gum (76.2% purity) were successfully

made at a level of the gum that provides 0.3 to 0.7% β-glucan in the product. 32 It appeared that the main advantage of β-glucan gum is the improvement of the water binding within a meat system, without having any significant effect on product texture or flavor if added at a 0.3% level to the breakfast sausage formulations. Low- fat white-brined cheese has also been manufactured from bovine milk (70% fat reduction) containing two levels, 0.7 and 1.4% (w/w), of a commercial oat β-glucan concentrate with 22.2 and 20.7% β-glucan and amylodextrin content, respectively. 37 For the cheese made with the β-glucan concentrate the yield, the extent of proteol- ysis, and the levels of short-chain fatty acids (lactic, acetic, and butyric) increased compared to the low-fat control products. Large deformation mechanical testing and the sensory ratings showed an improvement in texture of the low-fat cheeses con- taining β-glucan concentrates, with no significant differences between a full fat control and the low-fat cheese with a 0.7% level of β-glucan concentrate. However, the color, flavor, and overall impression scores were significantly inferior to those of a typical white-brined cheese product, particularly for the product made with a high level of β-glucan concentrate (1.4%).

Efficient, selective, and economical methods have been patented 208 for producing lactose-free, nondairy, ready-to-use milk substitute (oat milk beverage, yogurt, ice

cream, oat-based cream, whipped cream, and buttermilk) cereal dispersions having intact β-glucans, proteins, and natural sugars, as well as playing the role of stabilizer, while retaining the aroma and flavor of natural cereals. The dispersions prepared from synergistic enzymatic hydrolysis can be homogenized, subjected to UHT, and aseptically packaged or pasteurized and kept refrigerated until used or evaporated and subsequently spray dried to yield a stable powder.

Salovaara and Kurka 209 manufactured a snack food, yogurt-like, fermented prod- uct, based on oat bran (~5% v/v), containing living microorganisms (Streptococcus thermophilus , Lactobacillus bulgaricus, Lactobacillus acidophilus, Lactobacillus casei ); this product was tasty and combined two health benefits, dietary fibers and

46 Functional Food Carbohydrates

probiotic microorganisms. Recently, it has been introduced into the market as a functional snack food from oat bran having a texture like yogurt, but totally free from milk or other animal products; this product can be associated with beneficial health effects because it is a good source of β-glucan (0.75 g per serving), low in fat (0.7 g/100 g), lactose-free, and cholesterol-free, as well as containing the probiotic bacteria Bifidobacterium lactis Bb12 and L. acidophilus LA5. 210

In recent studies, the possibility of incorporation of cereal β-glucan preparations into beverage (fruit juice) and soup (shrimps and dill, mushrooms, lentil with ham) food prototypes, as well as the consumer acceptability of such products, has been

examined. 33 The molecular weight of β-glucan had a significant effect on the sensory thickness of the beverage and soup samples containing β-glucan. From a techno- logical point of view, the more processed β-glucan preparations are easier to be incorporated into a beverage and soup system in amounts sufficient for achieving a

physiologically functional amount of β-glucan in a product. 33 However, the relation- ship between physiological functionality and molecular weight also has to be kept in mind. Incorporation of cereal fractions corresponding to 4 g of β-glucan in one serving of soup (400 g) or 5 g of β-glucan in 500 ml of beverage is feasible from

a technological — as well as from a product acceptance — point of view. 190 Gen- erally, food products with added β-glucans must be carefully designed, because for consumer acceptability, the health benefit perception of such products might not be enough to counterbalance a poor taste of the formulation.

Morgan 151 proposed the use of a low molecular size barley β-glucan isolate, obtained by water extraction without deactivation of the endogenous enzymes and

a process of freezing–thawing, as a food additive in several applications. In addition to the incorporation of this β-glucan isolate into food formulations such as cakes, an Italian-style dressing (2% w/v) as a fat mimetic, and ice cream (5% w/v) for inhibition of ice crystal formation and keeping the smooth mouth feel, Morgan 151 has suggested its potential use as film-forming agent and a matrix for slow release

(encapsulation). Skendi et al. 43 confirmed the film-forming ability of β-glucans and found the observed range of tensile strength values (20 to 80 MPa) for oat β-glucan films to be comparable to many medium-strength commercial synthetic films, mak- ing them potentially useful as a biodegradable edible food packaging material. These researchers found that the mechanical properties of the casted β-glucan films are affected from the amount of plasticizer (water, polyol) and the molecular size of the polysaccharide. Water as well as sorbitol, added as a co-plasticizer at a 15% (w/w) level, improved the extensibility, but decreased the mechanical strength of the β- glucan film. Moreover, all the mechanical parameters (tensile modulus and strength, percentage elongation) exhibited higher values for a high molecular weight sample than for a low molecular weight sample at certain moisture and sorbitol levels.