Effect of enzymatic hydrolysis modes on the stability of oat milk

Plant-based milk beverages, particularly oat milk, recently have gained popularity. However, due to their high starch content, these milk beverages made from oat flour or other grain flour are faced with the technological challenge of poor stability. Depending on the enzyme hydrolysis of oat flour, in this research, the addition modes of three types of amylase including added separately, order of addition, and added simultaneously were systemically investigated to provide technical support for the creation of high-quality oat milk. Firstly, the effects of the addition of amylases, including α-amylase (A), glucoamylase (B), and pullulanase (P) on the starch hydrolysis rate in oat flour were examined to determine the optimal enzyme dosage and hydrolysis time. Secondly, a series of oat milk was prepared by using hydrolyzed oat flours, which were separately hydrolyzed by simultaneously or gradually enzymatic hydrolysis with two or three types of amylases. The preparing process of the oat milk comprised slurrying (the hydrolyzed oat flour/ water: 1/12), gelatinization (100 ℃, 30 min), enzymatic hydrolysis, enzyme deactivation (100 ℃, 15 min), dispersion and pulverizing with the colloid mill, sieving (200 mesh), and then homogenizing (50 ℃, 50 MPa), pasteurization. Instruments such as viscometers, laser particle size analyzers, and stability analyzers were employed to explore the effects of synchronous and sequential dual-enzyme and triple-enzyme hydrolysis on the viscosity, centrifugal sedimentation rate, particle size, changes in backscatter scattering luminous (ΔBS), and stability kinetic index (TSI) of oat milk. The results indicated that compared to the oat milk produced through dual-enzyme hydrolysis, oat milk prepared through triple-enzyme hydrolysis exhibited higher viscosity (reaching 12 mPa·s), and an average particle sizes (D_4,3) ranging from 14.43 to 19.47 μm, lower ΔBS and TSI value, and higher stability. When comparing triple-enzyme synchronous and sequential hydrolysis, the oat milk obtained through sequential triple-enzyme hydrolysis demonstrated higher viscosity, with most ΔBS values below 0.5%. Specifically, the oat milk prepared by adding pullulanase in the first step and simultaneously adding α-amylase and glucoamylase in the second step exhibited the lowest TSI and the best stability. Regulating the addition sequence of amylases and the types of enzymes added simultaneously can significantly improve the stability.