Pasteurization of liquid egg products greatly reduces the standard plate count bacteria, destroys possible pathogenic bacteria, and prolongs the keeping time of the products according to McFarlane, Watson, and Goresline (1945), Winter, Stewart, McFarlane, and Solowey (1946), and Gibbons, Fulton, and Reid (1946. Freezing and storage of liquid egg products also reduce the viable bacterial count, but not to such an extent as pasteurization as shown by Xchneiter, Bartram, and Lepper (1943) and Wrinkle and Winter (1950).Pasteurization and freezing impair the value of egg products only slightly, if a t all, for making angel and sponge cakes and custards according to Miller and Vail (1943), Hanson, Lowe, and Stewart (1947), Slosberg, Hanson, Stewart, and Lowe (1948), and Miller and Winter (1950.The purpose of this investigation has been to obtain information on the effects of pasteurization and freezing of whole egg and yolk on their emulsifying properties and the stability of their emulsions when used in the production of mayonnaise.
EXPERIMENTAL PROCEDUREEgg Samples. Grade A shell eggs from the University flock were divided a t random into three groups. Group one eggs were dipped a t room temperature in an oil used for shell treating eggs. They were stored two t o three weeks in a household refrigerator at 40 t o 45"F.(4.4 t o 7.2"C.) until used. They served as the unfrozen egg control. They were broken out when ready for use and forced through a hand homogenizer, the same as group two eggs.Group two eggs were broken out, forced through a hand homogenizer, and divided into two lots. Lot one was packaged in pint freezer tubs, frozen a t --20"F.(-29"C.) and stored a t 0"F.(-17.S°C.) for two to three weeks until used. The other lot was pasteurized according to the method used by Winter, Greco, and Stewart (1946) for four minutes, part a t 140 to 142"F. (60.0 to 6l.l0C.), part a t 142 t o 144"F.(61.1 to 62.2"C.), and the remainder at 144 t o 146"F. (62.2 to 63.3"C.). The pasteurized samples were then packaged, frozen, and stored the same as the unpasteurized lot.The yolk was homogenized, separated into two lots and treated the same as the whole egg.Standard plate bacterial counts were made according to the method of the Association of Official Agricultural Chemists (1945). Coliform counts were made on desoxycholate agar according to the method used by Leifson (1935).Group three eggs were broken out and the whites and yolks separated.Bacterial Analysis.