Stability of commercial phytase sources under different environmental conditions

Abstract

A 300-d study was conducted to evaluate storage stability of 4 commercially available phytase products under varied environmental conditions. Products used were: 1) Quantum Blue G (AB Vista, Plantation, FL), 2) Ronozyme Hi Phos GT (DSM Nutritional Products, Parsippany, NJ), 3) Axtra Phy TPT (Dupont, Wilmington, DE), and 4) Microtech 5000 Plus (Guangdong Vtr Bio-Tech Co., Ltd., Guangdong, China). Products were stored as pure forms, in a vitamin premix, or a vitamin trace mineral (VTM) premix. Pure products were stored at -20 degrees C, 4 degrees C, 22 degrees C, or 35 degrees C (75% humidity). Vitamin and VTM premixes were stored at 22 degrees C or 35 degrees C (75% humidity). Samples were stored in open-topped paper bags and sampled on d 30, 60, 90, 120, 210, and 300. Stability was determined as the amount of residual phytase activity (% of initial) at each sampling point. For the pure forms, all interactive and main effects of phytase product, time, and storage temperature were significant (P < 0.05). From d 30 to 300, products had similar reductions in phytase activity at the 3 highest temperatures; however, Quantum Blue G, Ronozyme HiPhos GT, and Axtra Phy TPT had reduced (P < 0.05) phytase activity as compared to Microtech 5000 at -20 degrees C. In general, as storage time increased, residual phytase activity decreased (P < 0.05) regardless of product and storage temperature. When product was stored at 4 degrees C and 22 degrees C, phytase activity was greater than that of product stored at -20 degrees C or 35 degrees C, and Microtech 5000 Plus had greater (P < 0.05) stability regardless of time and temperature as compared to the other 3 products. For vitamin and VTM premixes, a time x temperature x product interaction (P < 0.05) was observed. When stored at 22 degrees C, Axtra Phy TPT and Microtech 5000 Plus had reduced residual phytase activity (P < 0.05) when compared to the other 2 products; however, when stored at 35 degrees C Axtra Phy had even further reduced (P < 0.05) activity than the other 3 products regardless of which form the products were stored in. From d 30 to 300 Axtra Phy TPT and Microtech 5000 Plus had the lowest (P < 0.05) residual phytase activity when compared to the others regardless of storage form or temperature. Phytase products stored in VTM premix had decreased (P < 0.05) residual phytase activity when compared to pure products and vitamin premixes. In conclusion, phytase stored for longer than 90 to 120 d, at both high (35 degrees C) and low (-20 degrees C) temperatures when in pure form or as a VTM premix had reduced residual phytase activity.