Protease activities of extracts from kiwi of various colors and their use as a tenderizer in cured pork loins

The aim of this study was to evaluate protease activities of kiwi extracts with various colors (red, green, gold) and determine physicochemical and textural properties of pork loins added with such kiwi extracts during storage at 8°C for 24 h. Green and gold kiwi extracts exhibited higher protease activities than red kiwi extract using casein as a substrate. Pork loin was injected with 5% or 10% of red, green, or gold kiwi extract. Shear force were was decreased when kiwi extracts were added. When 10% of green or gold kiwi extract was added to pork loin, the tenderness increased with increased incubation time, which was confirmed by myosin heavy chain (MHC) band in sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE). These results indicate that green and gold kiwi extract could be used as a tenderizer for though meat through proteolytic activities of enzymes contained in kiwi. Novelty impact statement Green and gold kiwi extracts exhibited higher protease activities than red kiwi extract. When 10% of green and gold kiwi extracts were added to pork loin, the tenderness increased with incubation time. This study demonstrates that green and gold kiwi extracts could be used as a meat tenderizer without affecting the physicochemical properties of meat products.