Presentation Title

Strategies for improved binding of milk proteins with orange polyphenols for reduced bitterness

Faculty Mentor

Olive Yao Li

Start Date

17-11-2018 10:30 AM

End Date

17-11-2018 10:45 AM

Location

C164

Session

Oral 2

Type of Presentation

Oral Talk

Subject Area

biological_agricultural_sciences

Abstract

Orange pomace (containing peel, seeds, and pulp) is a by-product of the juice processing industry, accounting for over half the weight of the whole orange. While traditionally orange pomace has been used as animal feed, it is a source of high-value polyphenols. Nevertheless, several of these polyphenols (polymethoxylated flavones, limonoids, or naringin) may contribute to the bitter taste of orange pomace extracts. The current study utilizes the protein-binding capacity of polyphenols to create complexes which mitigate interactions with bitter taste receptors. Whey protein, micellar casein, and potassium caseinate were blended with the extract during the ultrasonic extraction of orange pomace in concentrations ranging from 1.7% to 5%, freeze dried, and ranked, qualitatively, in terms of bitterness and solubility. Furthermore, both the supernatant and the precipitated protein fractions were tested. The results indicated that, of the proteins tested, the precipitated fraction of potassium caseinate, at a concentration of 5%, reduced bitterness while maintaining solubility in water. In addition, a calibration curve was developed for the Folin-Ciolcalteu assay for total phenolic content. This calibration curve was utilized to develop and validate a procedure for quantifying protein-polyphenol binding through centrifugal ultrafiltration. Then, reduced pH, heating and/or ultrasound are applied to both whey protein isolate and potassium caseinate to alter their tertiary structure, thus exposing hydrophobic amino acids. No significant differences were observed between heat treatments or ultrasound for whey protein isolate, yet protein binding was observed for all treatments. Current and future research is focused on assessing the effects of pH and protein concentration. Protein binding of flavonoids from the crude extract will also be compared to that of pure gallic acid. Through these results, it may be possible to utilize orange pomace as an economical source of antioxidants, with palatable taste.

Summary of research results to be presented

Key results include that a minimum of 3.3% potassium caseinate was sufficient to reduce bitterness of orange pomace extracts. In addition, extracts were found to contain 0.42±0.5 mg gallic acid equivalents (GAE) per mL of extract. When filtered through a 1 mL 3k Dalton centrifugal filter at 4000 rpm, there was negligible protein permeation and free polyphenol permeation of 97±5%, indicating that ultrafiltration can be used to separate bound polyphenols from free polyphenols. When 5% potassium caseinate was hydrated with aqueous orange pomace extract for 24 hours, 0.205 mg GAE can bind per gram of protein. In addition, it was found that hesperidin must be present in approximately 100 times the concentration of gallic acid to achieve an equivalent measure of phenolic content. When heating and/or ultrasound were applied to whey protein isolate, there were no significant differences between treatments.

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Nov 17th, 10:30 AM Nov 17th, 10:45 AM

Strategies for improved binding of milk proteins with orange polyphenols for reduced bitterness

C164

Orange pomace (containing peel, seeds, and pulp) is a by-product of the juice processing industry, accounting for over half the weight of the whole orange. While traditionally orange pomace has been used as animal feed, it is a source of high-value polyphenols. Nevertheless, several of these polyphenols (polymethoxylated flavones, limonoids, or naringin) may contribute to the bitter taste of orange pomace extracts. The current study utilizes the protein-binding capacity of polyphenols to create complexes which mitigate interactions with bitter taste receptors. Whey protein, micellar casein, and potassium caseinate were blended with the extract during the ultrasonic extraction of orange pomace in concentrations ranging from 1.7% to 5%, freeze dried, and ranked, qualitatively, in terms of bitterness and solubility. Furthermore, both the supernatant and the precipitated protein fractions were tested. The results indicated that, of the proteins tested, the precipitated fraction of potassium caseinate, at a concentration of 5%, reduced bitterness while maintaining solubility in water. In addition, a calibration curve was developed for the Folin-Ciolcalteu assay for total phenolic content. This calibration curve was utilized to develop and validate a procedure for quantifying protein-polyphenol binding through centrifugal ultrafiltration. Then, reduced pH, heating and/or ultrasound are applied to both whey protein isolate and potassium caseinate to alter their tertiary structure, thus exposing hydrophobic amino acids. No significant differences were observed between heat treatments or ultrasound for whey protein isolate, yet protein binding was observed for all treatments. Current and future research is focused on assessing the effects of pH and protein concentration. Protein binding of flavonoids from the crude extract will also be compared to that of pure gallic acid. Through these results, it may be possible to utilize orange pomace as an economical source of antioxidants, with palatable taste.