Recent Progress in Technologies for Enzymatic Peeling of Fruit

Enzymatic peeling of fruit and vegetables is considered superior to conventional peeling methods in terms of minimizing product damage and indeed is expected to improve them. This technology was first proposed for the peeling of citrus fruit and numerous studies on its practical use have been conducted. However, its application to non-citrus fruit and vegetables remains limited. A novel process, including heat treatment prior to enzymatic treatment, is proposed to peel persimmon fruit. Heat treatment induces fine and even cracks on the fruit surface of certain persimmon cultivars, which act as channels via which enzyme solution can enter the peel tissue. Another function of the heat treatment is to inactivate polygalacturonase-inhibiting protein (PGIP), which is inherent in persimmon fruit. Inactivation of PGIP improves the efficiency of enzymatic peeling with exogenous polygalacturonase. Chemical pre-treatments with a food-grade emulsifier solution and a weak basic solution also enhance the permeability of enzyme solution into the peel tissue. These physical and chemical treatments are useful for applying enzymatic peeling to various persimmon cultivars. In future, enzymatic peeling technology is expected to be applied to various agricultural crops as the technology is further refined. Discipline: Food Additional key words: cuticle, emulsifier, persimmon, polygalacturonase, wax This paper reports the results obtained in the joint project on “City Area Program 2009”, “Regional Innovation Cluster Program 2010” and “Regional Innovation Strategy Support Program 2011” sponsored by Ministry of Education, Culture, Sports, Science and Technology. Present address: 4 Collaboration and Public Relations Center, Headquarters, National Agriculture and Food Research Organization (NARO) (Tsukuba, Ibaraki 305-8517, Japan). *Corresponding author. e-mail: zhenji@affrc.go.jp Received 28 April 2014; accepted 19 January 2015. Introduction Enzymes are large molecules — mainly proteins — that catalyze specific chemical reactions. In contrast, most chemical catalysts catalyze a wide range of chemical reactions. Accordingly, in fruit processing, using enzymes has the advantages of preventing undesirable changes in material characteristics and the potential to retain the qualities of the raw materials. Traditionally, application of enzymatic reactions in fruit processing was limited to liquid obtained from pressed, crushed or homogenized fruit. However, the development of enzyme infusion technology (Baker 1996, McArdle 1994) has expanded the applicable scope of enzymes to include solid fruit, to maintain their form. One example of the application of enzyme infusion technology is enzymatic peeling of citrus fruit rind (Adams 1991, Bruemmer 1981). Enzymatic peeling of citrus fruit Enzymatic peeling technology was first proposed for the peeling of citrus fruit prior to that of non-citrus fruit for three reasons (Pretel 2010). The first reason pertains to fruit anatomy. Citrus fruit