Fruit enzymatic clarification

Ishii and Yokotsuka recently used pectin lyases from Aspergillus sojae 170, 171, 172) and Aspergillus japonicus (173) for the enzymatic clarification of fruit juices. This is discussed later in this review. Bush and Codner 174) compared the pectin lyases produced by Penicillium digi-tatum and Penicillium italicum and found them remarkably similar. Both were endo acting, had optimal activities at pH 5.5, and had the same K. The pectin lyase from F. italicum, however, was less stable than that of F. digitatum. Spalding and Abdul-Baki 175) reported the production of a pectin lyase by Penicillium expansum growing on apple tissue or a pectin-polypectate mixture. 

Fruit juice clarification by pectinases and cellulases is another interesting application. In the conventional process after the enzymatic reaction in the pulp treatment step takes place, filtration over diatomaceous earth follows. This filtration-type process produces a lot of solid waste, and results in costly enzyme loss. MBR are appropriate for such application either for enzyme recovery and recycle or in the form of a more compact CMR type system, with the biocatalyst immobilized on the membrane itself [4.58]. 

Cloud stability in citrus juices Pectin manufacture from citrus pomace Distillates from fermented fruit pulps Enzymatic maceration of fruits and vegetables Self-clarification of lemon/lime and apple juices Pressing characteristics of citrus pomace Ca2 -firming of fruits and vegetables... 

ENZYMATIC HYDROLYSIS OF STARCH. Starch is a substance used for storing energy reserve in plants, where it is deposited in the form of starch granules. Starch may be noticed in fruit juice as a milky haze. This haze disappears when the juice is heated, but re-appears after it is cooled to less than 10°C. Like pectin, starch has a protective colloid effect on suspended particles and thus makes juice clarification more difficult. 

Several years ago a flotation process for clarification of fruit juices was developed in Canada [6,6a]. The juice is enzymatically treated, bentonite is added and the mixture is impregnated with an inert gas (nitrogen, carbon dioxide). Then the liquid is pumped into an especially designed flotation tank in which the solids float to the top from where they can be skimmed off in concentrated form. The liquid is polished by filtration. This process was also tested in Europe. 

---