Eric Engstrom
Introduction
Milk is a nutrient dense food that cannot be utilized easily by those with lactose intolerance. Lactose-hydrolysis is a process through which the native lactose in milk is enzymatically converted into its constituent sugars, glucose and galactose. Because this process digests the lactose in milk, the milk can then be digested by consumers with lactose intolerance without adverse affect (Somkuti, 1997). This conversion results in a sweeter product (Fennema, 2008).
Chocolate milk products are common in the dairy market. These products are made by adding flavor and sweetener (sugar or artificial sweeteners) to milk. Since hydrolyzed milk is sweeter than non-hydrolyzed milk, it is proposed that chocolate milk could be produced with equal sweetness but less added sugars if the milk is first lactose-hydrolyzed. The purpose of this experiment was to determine quantitatively how much added sugar can be spared when chocolate milk is made using lactose-hydrolyzed milk.
Methods
To determine the amount of added sugar that could be spared, two sensory panels were conducted comparing lactose hydrolyzed milk with various sucrose concentrations to a control chocolate milk formula. A control was prepared using a basic chocolate milk formula (2% milk, cocoa, sucrose, and hydrocolloids) which was mixed and batch pasteurized. Experimental samples were prepared by treating 2% milk with lactase enzyme (Danisco) according to the method used by Horner (2010) to approximately 99.9% hydrolysis. Enzyme treated milk was then used in the same chocolate milk formula used for the control with varied amounts of sucrose (all other components kept constant). These samples were batch pasteurized and combined in ratios leading to multiple samples with a range of final sucrose concentrations. All samples were then given blinding codes and were served in pairs containing one experimental sample and one control sample. Panelists were asked to identify which of the two samples were sweeter . Statistical analyses were performed on the data using Compusense® Five.
Results and Discussion
Results from the panels were compared using a Friedman analysis of rank. In general, panelists were able to identify the control sample as being sweeter when the lactose hydrolyzed sample contained a relative added sugar of 70% or less. At 85% or more relative sugar added panelists were able to identify the lactose hydrolyzed milk as being sweeter. At 74, 78, and 82% panelists were unable to determine which sample was sweeter, indicating that equivalent sweetness was somewhere in this range.
A whole model regression test was later used to determine the relative percent sugar added at which we would expect exactly fifty percent of panelists to choose either sample as sweeter. This “equivalent sweetness” was calculated to be at 80.6% (78.0-85.7) the amount of added sugar (ie, about a 20% sugar reduction).
Conclusion
An added sugar reduction of 20% is the equivalent of lowering the added sugar in an 8 oz. serving of chocolate milk from ~17 g sucrose to ~13.5 g sucrose or lowering the total sugars from 29 g to 25 g in an 8 oz. serving. This reduction of sugar would lead to a marginal change in production costs, but could be a desirable attribute for consumers interested in lower carbohydrate and calorie dairy products. More research still needs to be performed to determine the effect of lactose hydrolysis on product sweetness in other food matrices such as ice cream or yogurt. This work will hopefully be performed by undergraduate students in the food science department.
Works Cited
- Fennema, O., S. Damodaran, and K. Parkin. 2008. Fennema’s Food Chemistry. 4th ed. Boca Raton, FL. CRC Press. 1144 p.
- Horner, TW. 2010. Beta-galactosidase activity of commercial lactase samples in raw and pasteurized milk at refrigerated temperatures [MSc thesis]. Provo, UT: Brigham Young Univ. 117p. Available from: Lynn Ogden, lynn_ogden@byu.edu
- Somkuti, G. A. and V. H. Holsinger. 1997. Microbial technologies in the production of low-lactose dairy foods. Food Science and Technology International 3(3):163-169.