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Purple Corn (Zea mays L.) Cob Anthocyanins: Extraction, Quantification, Spray Drying and Complexation with Proteins

Lao, Fei
http://rave.ohiolink.edu/etdc/view?acc_num=osu1469116741

Abstract Details

2016, Doctor of Philosophy, Ohio State University, Food Science and Technology.
Interests of applying natural colorants such as anthocyanins as alternatives to synthetic dyes in food have been a market trend in recent years. This study evaluated purple corn cob (PCC) as economic natural source for high quality food-used anthocyanins colorant production. PCC is an anthocyanin-rich plant source. Different from anthocyanins in other fruits and vegetables, production and application of PCC anthocyanins is not as simple and straightforward due to the fiber-rich hard texture of the cob and relatively complicated biomatrix of the corn. Some of the PCC pigments undergoing traditional processing have acidic water solubility issues, which limit their application in most aqueous-based foods. The objective of this study is to optimize preparation of PCC anthocyanins, to produce high quality PCC pigments for more general food application. To achieve this goal, the critical conditions in PCC pigments extraction and spray drying were evaluated, and the key structure (anthocyanin-protein complexation) which was believed to be correlated to water solubility problems was investigated using infrared spectroscopy. Aqueous ethanol with water and ethanol ratio around 1:1 with slightly acid addition (0.01% v/v HCl) was able to efficiently recover PCC anthocyanins and phenolics. The yield was comparable to analytical labolatory used solvents under the same extraction conditions. Spray drying PCC pigments with mild inlet/outlet temperatures (150°C/105°C) and appropriate amount (5%, m/v) of carrier could produce satisfactory quality PCC pigment powders with least color degradation and more than 85% of pigment yield. The only hazy reconstituted PCC pigment solution was obtained from spray drying alcoholic PCC extract, which suggested the acidic water insolubility issue was mainly coming from the extraction rather than the heated dehydration process. Anthocyanin-tannin-protein complex was proposed in previous studies to be the major contributor in the insoluble PCC pigment rich particles. Confirmed by the mid infrared (MIR) spectroscopy, the PCC anthocyanins and protein could form complexation in the aqueous matrix. Hydrogen bonding was the major driving force to stabilize the complexation. The anthocyanin:protein molar ratio in the complexation depended on the environmental pH, as hydrophobic interaction and ion chelation might also be involved into complexation when the matrix pH was acidic. A rapid MIR prediction model to quantify protein levels in anthocyanin-rich matrix was also developed based on protein unique Amide signals. In addition, the present study also discussed the advantages and disadvantages of four commonly used anthocyanin quantification methods in PCC pigment analysis. All four spectrophotometric and HPLC approaches outcomes for PCC were linearly correlated (R2=0.90) to each other. The total anthocyanins methods produced highest values, followed by the pH differential method, HPLC method with intact pigments, and HPLC method with acid hydrolyzed pigments. Overall, our study showed PCC could be used to produce high quality anthocyanin powders ready for food application, as well as provided important insightful understandings on anthocyanin-protein complexation. Information in this study may help food companies interested in the transition from synthetic dye to natural colorant using PCC, for cleaner and more consumer-friendly labels.
M.Monica Giusti (Advisor)
Sheryl Barringer (Committee Member)
C. Lynn Knipe (Committee Member)
John Litchfield (Committee Member)
242 p.
Food Science
anthocyanin; extraction; HPLC-MS; spray-drying; color; anthocyanin-protein complex

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Citations

  • Lao, F. (2016). Purple Corn (Zea mays L.) Cob Anthocyanins: Extraction, Quantification, Spray Drying and Complexation with Proteins [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469116741

    APA Style (7th edition)

  • Lao, Fei. Purple Corn (Zea mays L.) Cob Anthocyanins: Extraction, Quantification, Spray Drying and Complexation with Proteins. 2016. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1469116741.

    MLA Style (8th edition)

  • Lao, Fei. "Purple Corn (Zea mays L.) Cob Anthocyanins: Extraction, Quantification, Spray Drying and Complexation with Proteins." Doctoral dissertation, Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1469116741

    Chicago Manual of Style (17th edition)

osu1469116741
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This open access ETD is published by The Ohio State University and OhioLINK.