48—JOURNAL OF FOOD SCIENCE—Volume 62, No. 1, 1997 Improved Emulsifying and Foaming of Whey Proteins after Enzymic Fat Hydrolysis C. BLECKER, M. PAQUOT, I. LAMBERTI, A. SENSIDONI, G. LOGNAY, and C. DEROANNE ABSTRACT In an effort to improve emulsifying and foaming of sweet whey and whey protein concentrate, we studied the hydrolysis of the residual fat in these preparations with a sn 1,3 specific lipase. This enzymatic lipol- ysis would convert almost all triglycerides into mono- and diglycerides which have strong surface-active properties. Therefore, the emulsifying and foaming capacities of such modified whey products should be in- creased in comparison with native products, as shown by results pre- sented at both neutral pH and those similar to a salad dressing emulsion. It was also demonstrated that emulsions and foams formed with lipase- treated whey preparations were more shelf-stable. Key Words: whey, lipase, functional properties, emulsion, foam INTRODUCTION THE FOOD PROCESSING INDUSTRY utilizes protein ingredients to provide specific functional properties to a wide range of for- mulated foods. Whey protein products and whey protein con- centrates (WPC) represent an important and valuable source of ingredients due to their effective nutritional (Adrian, 1973), sen- sory and functional properties including, principally, water ab- sorption, gel formation, emulsification and foaming (Cheftel and Lorient, 1982). Food products for which whey is useful are emulsions and foams (Peltonen-Shalaby and Mangino,1986) such as dressings and sauces, finely comminuted meat and fish products, low-calorie desserts, ice-cream, snacks and confec- tionery products (De Wit and Hontelez-Backx, 1981; Zwijgens, 1992). Emulsification and foaming are governed by the physi- cochemical properties of whey proteins and can vary, depending upon many factors: Treatment of the whey proteins, mainly -lactalbumin and - lactoglobulin can be modified by different physical, chemical or enzymic treatments (Modler, 1985). Heat denaturation of whey proteins alters surface characteristics and hence related func- tional properties. Heat processing of WPC modifies protein sol- ubility and the ratio of -lactalbumin and -lactoglobulin which influence gelation and emulsification (Beuschel et al., 1992; Mu- tilangi et al., 1996). It has also been pointed out that mild heat treatments (up to 60°C) may reversibly affect the solubility and foaming properties of whey proteins (De Wit and Klarenbeek, 1984), but at higher temperatures (up to 70°C) the foaming effects decrease sharply (Richert et al., 1974). Chemical modifications like succinylation, amidation, phosphorylation, esterification and use of thiol-reducing agents modify functional properties (Kester and Richardson, 1984), but usually with a reduction of nutri- tional value. Enzymatic modification generally involves prote- olytic hydrolysis resulting in a peptide mixture. Functional behavior usually depends upon the extent of hydrolysis (Vega- Authors Blecker, Paquot, and Deroanne are with Faculte ´ Univer- sitaire des Sciences Agronomiques de Gembloux, U.E.R. de Tech- nologie des Industries Agro-alimentaires. 2, Passage des De ´ porte ´ s, B-5030 Gembloux, Belgium. Authors Lamberti and Sen- sidoni are with the Universita degli studi di Udine, Facolta di Agraria, Instituto di Tecnologie Alimentari. 97, Via Marangoni, 33100 Udine, Italy. Author Lognay is with the Faculte ´ Universitaire des Sciences Agronomiques de Gembloux. U.E.R. de Chimie Ge ´- ne ´ rale et Organique, Gembloux, Belgium. Address inquiries to Dr. M. Paquot. rud et al., 1991; Turgeon et al., 1991). Specificity of enzyme and conditions of hydrolysis are critical in avoidance of bitter flavors (Modler, 1985). Variation in emulsification and foaming properties of whey products has also been related to residual lipid. Residual lipids generally inhibit the ability of whey proteins to function in foaming applications (De Wit, 1975; Burgess and Kelly, 1979; Morr, 1985). The presence of lipids modifies rhe- ological properties of the interface. From a physicochemical view, protein stabilization of foams and emulsions is based upon the formation of a stiff viscoelastic, adsorbed layer at the air- water (a/w) or oil-water (o/w) interfaces. The strength of this adsorbed layer is dependent upon the degree of interaction between neighboring protein molecules. High levels of protein- protein interactions at the interface result in a strong, viscoelas- tic, adsorbed layer. Such a structure resists deformation and will sterically hinder coalescence, resulting in a highly stable foam or emulsion. However, in the presence of fats, the strength of the adsorbed layer is reduced, along with the stability of the foam or emulsion. This is because the lipid components adsorb alongside the proteins, decrease the level of interaction between protein molecules, and reduce the strength of the adsorbed layer. This less resilient interface is more susceptible to rupture, re- sulting in increased coalescence and unstable foams or emul- sions (Clark et al., 1993; Mackie et al., 1993; Coke et al., 1993). Such fundamental explanations are supported by the practical experience that defatted whey concentrates have good whipping and foam stability characteristics for use in meringues, frappe ´s and whipped toppings (De Wit et al., 1983). Because of the depression of residual fat on functional performances of whey, it has been recommended to eliminate fat. It is however difficult to remove all residual lipids from WPC (Kilara, 1994). Many investigators have successfully applied pretreatments to produce WPC with reduced lipid and improved functional properties. Among these, Rinn et al. (1990) evaluated nine semi-pilot-scale physical pretreatment modifications involving various combi- nations of centrifugal clarification and/or microfiltration to remove residual lipids and phospholipoprotein complexes. Also, chemical pretreatments, microfiltration and ultrafiltration have produced delipidized WPC (Karleskind et al., 1995a). The heat- induced gelation, emulsifying and foaming properties of such experimental calcium and lipid-reduced WPC were quite differ- ent from those of experimental and commercial WPC (Karles- kind et al., 1995b; Karleskind et al., 1996a,b). As an interesting alternative to defatting, Blecker et al. (1995) suggested modi- fying residual fat in whey by enzymic hydrolysis with a sn 1,3 specific lipase to produce mono- and diglycerides to enhance emulsifying and foaming properties. The interfacial properties of such transformed whey imply that such a product would be more suitable for emulsification and foaming than the unmodi- fied whey. The objective of our investigation was to confirm this assumption. We report on the effect of residual fat hydrol- ysis upon emulsifying and foaming properties of sweet whey and WPC. MATERIALS & METHODS Whey protein products Commercial sweet whey powder was obtained from Franche-Comte ´ Serum (Port-sur-Saone, France); dry matter 96.8%, protein (N  6.25)