The use of milk protein concentrates with high water activity in the manufacture of high protein nutritional bars

Abstract

Milk protein concentrate (MPC) is extensively used in food formulations due to its physical, chemical, sensory, and functional attributes. However, when utilized in nutrition bars, they are often not shelf stable longer than 6 months due to increased hardening. Matching the water activity of MPC to other ingredients in the nutritional bars can help mitigate moisture migration and aid in the reduction of bar hardening during storage. In this study, an adsorption and desorption method were used to produce high water activity MPCs. In the adsorption method, three lots of MPC 85 were split into control and treatment batches to produce 1-inch square high protein nutrition bars (HPNBs) with (1) no MPC modification with a water activity of approximately 0.2 or (2) MPC modification with a water activity of approximately 0.5. HPNBs were stored in two different temperatures: 25ºC and 36ºC and tested in triplicates on days 1, 2, 4, 6, 13, 22, and 31. In the desorption method, three lots of liquid MPC 85 were produced from skim milk, split into control and high-water activity batches and spray dried to produce 1-inch square HPNBs with (1) no MPC modification with a water activity of approximately 0.2 or (2) MPC with a high-water activity of approximately 0.5. HPNBs and were stored in two different temperatures: 25ºC and 36ºC. HPNBs were tested in triplicates on days 3, 6, 13, 22, and 28. The physical and chemical changes of HPNBs during storage were monitored using different analytical tests. Compared to control HPNBs, the HPNBs produced with water activity adjusted MPC 85 or high-water activity MPC 85 showed no differences in chemical and physical characteristics during storage 25ºC. However, at 36ºC the water activity adjusted and high-water activity MPC did affect the rate of moisture migration and Maillard browning. Thereby, reducing the rate of HPNB hardening.