Stability of corn cobs extract in powdered and concentrated form

Abstract

An attempt to utilize the agricultural by-products is getting interested from many
researchers and factory owners. Corn cob is one of an agricultural by-product that can be
found generally in Thailand and contains valuable phenolic acids such as ferulic acid and
coumaric acid. Extraction of phenolic compounds for food application is an alternative way
to add value of the agricultural by-products due to its physiological functions on human
health and can be used as functional ingredient. However, a research paper related with
stability of corn cobs extract in different forms during storage time is limited. Therefore, this
research was to study on the stability of corn cobs extract in powdered form (by freeze
drying) and concentrated form (by vacuum evaporation) during storage for 12 weeks at 4°C.
Corn cobs were extracted using alkaline treatment prior to lignin and hemicellulose
precipitation by using ethanol. The samples were taken every 2 weeks to analyze the
physical and chemical properties including color measurement, antioxidant activity using
DPPH method, and total phenolic content using Folin-Ciocalteu method. The results showed
that all properties of those corn cobs extract in powdered and concentrated form
significantly changed during storage (P≤0.05). Compare to an initial week (week 0), total
phenolic content started changing at week 2 which the powdered sample decreased about
2.26% (ranged from 2.26 to 12.58% until week 12) and concentrated sample decreased
about 3.95% (ranged from 3.95 to 6.50% until week 12). In terms of the antioxidant activity,
IC50 started changing at week 4 which the powdered sample decreased about 21.41%
(ranged from 20.75 to 36.08% until week 12) and concentrated sample decreased
about 14.39% (ranged from 13.68 to 24.03% until week 12). It can be concluded that the
decreasing trend during 12 weeks of storage of the powdered sample showed higher than
that of concentrated form. Therefore, for further use of the corn cobs extract as a functional
ingredient, it was no need to make the extract solution in the powdered form.