The study, published in Innovative Food Science and Emerging Technologies, suggests that it is possible to produce pectinolytic enzymes, which break down plant cell walls, for fruit juice clarification using the cheaper raw pectin rich substrates, at low temperatures.
Researchers from the Department of Microbiology at Osmania University, India, identified a yeast isolate (Saccharomyces sp.) which has good growth and enzyme production at low temperatures. They said that the clarification of fruit juices at low temperature by cold active polygalacturonase (PGU) enzymes and low cost fruit wastes as substrates is cost effective, and reduces the risk of spoilage from high processing temperatures.
“This isolate could be exploited for cold-active polygalacturonase (PGU) production using fruit wastes as substrates … Cold active PGU enzyme production at 250C was good with cheap raw pectin substrates like orange peel, apple peel and mango peel …which are wastes from fruit processing industry,” said the authors, led by Gopal Reddy from Osmania University.
“This is commercially very important as the use of cheaper raw materials reduces the production costs significantly,” they added.
Clarification
Pectinolytic enzymes (or pectinases) are enzymes that break down pectins in the primary cell walls of plant tissues. The enzymes have widespread applications in the food industry – where they are mainly used for the clarification of fruit juices, wines, coffee and tea fermentations, and the extraction of essential oils.
Reddy and colleagues explained that commercial pectinases of fungal origin are generally a mixture of enzymes including polygalacturonases (PGU), pectin lyases and pectin esterases; however they noted that esterases are “undesirable” in food and beverage manufacturing as they also produce methanol as end product.
Yeasts are also known to produce pectinases, especially polygalacturonases. The authors explained that pectinases produced by yeasts are preferred as commercial production strains because the yeast isolates are generally recognised as safe (GRAS) for food production, and also have shorter fermentation cycles. The fermentation cycle of yeasts is between 18 and 24 hours, whereas those of molds and fungus are over 48 hours.
Reddy and co-workers said that cold-active enzymes “are attractive for usage in [the] fruit juice industry as colder conditions hamper spoilage and favour milder conditions that avoid changes in organoleptic and nutritional properties.”
They said that in particular cold-active polygalacturonases are very useful for fruit juice clarification.
The new study screened the activity of yeasts with cold-active pectinolytic enzymes, and the best isolate was studied for growth and production of polygalacturonase (PGU) at low temperatures.
Cold production
The Indian scientists screened isolates from pectin rich spoiled fruits and vegetables (cold stored), and cold soils. Six yeast isolates with high pectin hydrolysis were identified from the screening process and tested for PGU production and activity at room temperature (250C) and at 50C.
One yeast isolate – later identified as Saccharomyces sp. – was found to have good growth at both 250C and 50C, and was found to efficiently produce cold-active PGU enzymes at room temperature.
Reddy and colleagues explained that the cold-active PGU produced by Saccharomyces sp in the presence of ‘fruit wastes’ could have applications in fruit juice clarification, as the cold –active enzymes allow for milder conditions that would prevent spoilage.
The enzyme in turn could be used in fruit juice clarification under cold or milder conditions which is cost effective at large scale application.
“This is a significant observation as the enzyme can be produced commercially at room temperature and used … under cold and milder conditions,” said the authors.
Source: Innovative Food Science and Emerging Technologies
Published online ahead of print, doi: 10.1016/j.ifset.2011.02.001
“Pectinolytic yeast isolates for cold-active polygalacturonase production”
Authors: P.N. Padma, K. Anuradha, G. Reddy