Technical Abstract: Traps baited with synthetic food-based lures that include blends of ammonia, either as ammonium acetate or ammonium bicarbonate, and putrescine capture a number of Anastrepha and Bactrocera species fruit flies. However, for many of these species, more flies are captured in traps baited with the protein bait Nulure combined with borax in an aqueous solution, typically 9% Nulure (v/v) with 3% borax (sodium tetraborate decahydrate; wt/v). Nulure is acid-hydrolyzed corn protein product and has an acidic pH. Addition of borax makes the solution more alkaline, and increase in alkalinity results in increase in ammonia release from the bait. This is a very dynamic system, with resultant pH affected by factors such as pH of the water used to make the aqueous solution, amount of borax added and age of the solution. As part of research to developed improved lures and baits for Anastrepha and Bactrocera species fruit flies, research was conducted to develop a protein lure that is user-friendly, storable, and can be adjusted to attract target fruit flies. Experiments were conducted on the effect of pH on proteinaceous baits over time. It was observed that the zwitter ion effect plays a critical and confounded role on pH stability in aqueous solutions. Results are presented on pH in a range of pH4 to pH10 over time. It was discovered that the pH of solutions could be stabilized when propylene glycol was added at a 10% (v/v) concentration and sodium hydroxide could be used to adjust the pH. This discovery may provide an environmentally safe alternative to the use of borax.