Proteases from Aspergillus oryzae have good proteolytic action against both collagen
and elastin. This multiple action on different proteins is due to the enzyme preparation
having a variety of protease activities, including: alkaline proteinase (EC 3.4.21.14), aspartic proteinase (EC3.4.23.6), and neutral proteinase (EC 3.4.24.4)
(GRAS notice 000090; FDA-CFSAN, 2007). Because the products contain a collection
of enzymes that are active over a very wide pH range and have a moderate temperature
of denaturation (70°C), proteases from A. oryzae make it easy to control the
extent of meat tenderization. The primary protease originating from A. niger is an
aspartic proteinase (EC 3.4.23.6). Proteases from some Aspergillus spp. can exhibit
some degree of amylase side activity, which can pose a problem in products that
contain starch. Because of this side activity and high production costs, these enzymes
have not gained widespread use as tenderizing agents in the meat industry. However,
some of the neutral proteases from A. oryzae have found use as debittering agents
(Sumantha, Larroche, & Pandey, 2006). Ashie, Sorensen, and Nielsen (2002) studied
a specific aspartic protease and reported that it improved meat tenderness by 25–30%.
The enzyme had a relatively low temperature of inactivation (60°C), was not
adversely affected by normal meat pH and ingredient combinations, and tenderizing
activity was expressed primarily during cooking and not during storage.
