Pectic enzyme preparations, commercial

Freshly pressed apple juice contains about 0.15% pectin (actual amounts vary considerably, depending on variety, ripeness, etc.) in colloidal suspension. This pectin is closely associated with insoluble particles and causes them to remain suspended in the juice. The haze is difficult to remove by conventional filtration or centrifugation. If an appropriate amount of a commercial pectic enzyme preparation is added to freshly pressed juice, the haze begins to flocculate within a few minutes, and after several hours the floe settles out, leaving a relatively clear supernatant liquid. The juice is finished by centrifugation or filtration through diatomaceous earth (7, 180),... 

A third group of hydrolytic enzymes specific for highly methylated pectins (polymethylgalacturonase, EC 3.2.1.41) has been described particularly in the older literature prior to the discovery of the pectin lyase by Albersheim et al. (21). We have never been able to find either exo-PL nor endo- and exo-PMG in our extensive screening of commercial preparations and micro-organisms. Many authors now agree that enzymes described as endo-or exo-PMG may very well have been a combined PE-PG activity, or a PL activity or even PG activity alone in cases where only initial velocities were measured. Extensive reviews of pectic enzymes have been published (22-26). 

A practical technique for lactic acid fermentation of potato pulp has been developed (Oda et al., 2002). They screened 38 strains of the fungus Rhizopus oryzae either lactic acid or fumaric acid and ethanol were formed, and the ratio differed among the strains tested. Saito et al. (2003) studied the effect of pectinolytic enzymes on lactic acid fermentation of potato pulp by different Rhizopus oryzae NRRL 395 and NBRC 4707 strains. When a commercial preparation of pectinase was added to potato pulp inoculated with fungal spores and incubated for 7 days, both strains effectively produced larger amounts of lactic acid and ethanol. These data indicated that the fermentation of potato pulp depends on the degradation of pectic substances in NRRL 395 and NBRC 4707. Saito et al. (2006) evaluated the potato pulp obtained in different seasons and found pectin content to be dependent on the dates of extraction. 

The addition of pectolytic enzymes in crushed grapes can improve juice extraction for certain varieties very rich in pectic substances (Muscat, Sylvaner, etc.). Commercial preparations contain diverse enzymatic activities which are active at a low pH pectin methyl esterases, polygalacturonases, pectin lyases and hemicellulases. At a concentration of 2-4 g/hl, 15% more juice can be obtained during a settling period of 4-10 hours even a shorter settling period (1-2 hours) increases the proportion of free run (Table 11.8). Effectiveness varies according to the nature of the grapes. 

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