Chemistry Reference
In-Depth Information
Fig. 11.1
Pectin composition and pectin degrading enzymes (adapted from Ref. [13].)
the juice to speed up the process. Pectin is a polysaccharide present in every fruit that gels
after crushing. It holds the juice within the mash, reduces pressability, decreases juice yield,
slows down juice clarification and makes water evaporation for concentration impossible.
By chance, enzymes from
A. niger
are globally efficient at natural fruit pH, from 2.5 to
5.5. In addition, fruits and vegetables are processed in cool conditions to maintain freshness
(processing temperatures, in general, never exceed 50
◦
C). These factors are conducive to
pectinase use in juice processing. Classic
A. niger
strains produce pectinases as a core
activity, as well as numerous other enzymes such as hemicellulases or glycosidases as side
activities. All have a specific function and role to play in fruit processing. Juice processors
expect enzymes to be efficient, so it is imperative that the enzyme producer controls and
standardizes pectinase activity in every batch. Pectinases are produced from a pure culture
of one
A. niger
strain, selected on the basis of its productivity. Although the fungus species
is
A. niger
, strains differ and are the property of the enzyme producer. Strains are grown
in solid media (solid state culture) or liquid mediums (submerged fermentation). Enzymes
produced during the culture are strain- and medium-dependent, with variable and controllable
concentration, range and ratio of activities. This is why the enzyme range differs from one
commercial product to another, even if sold with the same name of pectinase or amylase.
Enzyme suppliers must therefore provide the user with complete information on: product
reliability, specifications, conformity with legislation, whether or not genetically modified
microorganisms were used and safety in use.
14
11.4.2 Specifications
An enzyme specification sheet and certificate of analysis describe product composition, stabi-
lizing systems, chemical properties, microbiological properties, stability and status (whether
