Stability of corn cobs extract in powdered and concentrated form

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.