Date of Graduation
Master of Science in Food Science (MS)
Luke R. Howard
Ron L. Prior
Second Committee Member
Anthocyanins, HPLC, Juice Processing, MALDI-TOF-MS, Polyphenolics, TLC
Chokeberry consumption has been increasing due to research exposing great potential of health-promoting compounds. However, chokeberries are highly astringent and are typically consumed in processed forms in which product heating is applied. Processing chokeberries has been reported to degrade bioactive compounds, thus limiting the potential for consumers to obtain their health-promoting benefits. The purpose of this research was to examine the effects of chokeberry juice processing and storage on anthocyanin, flavonol, proanthocyanidin, hydroxycinamic acid, and polymeric pigment content, as well as percent polymeric color. In addition, new analytical methodologies were explored to better understand possible outcomes of polymeric pigments due to juice processing and storage.
Chokeberries were processed into nonclarified juice with sampling at each stage of processing. Levels of anthocyanins, flavonols, proanthocyanidins, hydroxycinamic acids, and percent polymeric color were also analyzed each month throughout a 6 month storage period at ambient temperature. It was determined that anthocyanins readily degrade during juice processing, especially with heat applications during blanching and pasteurization. Comparatively, other compounds, such as proanthocyanidins were better retained during processing than anthocyanins, with significant levels remaining in the presscake. After pasteurization, lower levels of anthocyanins (7%), flavonols (52%), proanthocyanidins (55%), and hydroxycinamic acids (63%) remained in the juice. Alternatively, polymeric color values increased to 29% throughout processing. During juice storage, polyphenolic levels continued to decrease over 6 months while percent polymeric color values increased further to 44.5%. Little change occurred in levels of total flavonols (447.8 to 406 mg/100g), proanthocyanidins (19.7 to 16.5 mg/100g), and hydroxycinamic acids (72.7 to 48.9 mg/100g) over 6 months of storage.
After observing a 55% reduction in anthocyanins due to blanching frozen chokeberries, standard juice processing was altered by removing the blanch step and its effect on polyphenolics was evaluated. The effect of two different juice processes (with and without blanching) on anthocyanin, proanthocyanidin, flavonol, and hydroxycinnamic acid contents as well as percent polymeric color was evaluated at each stage of processing. Juice pasteurization times and temperatures were also evaluated to develop a statistical model that would predict optimal anthocyanin retention. In comparison of the two processes, there were no significant differences in anthocyanin content after pasteurization; however, samples receiving no blanch had higher levels of anthocyanins after enzyme treatment. Pasteurized juice samples receiving a blanch treatment had 37% and 16% higher levels of total proanthocyanidins and flavonols, respectively than pasteurized juice receiving no blanch treatment. A response surface model was designed for the prediction of anthocyanin retention with optimum pasteurization conditions of 74°C for 2.02 minutes.
MALDI-TOF-MS was used to identify large molecular weight proanthocyanidins and polymeric pigments throughout each stage of processing and over six months of juice storage. Proanthocyanidins and polymeric pigments having up to a degree of polymerization (DP) of 16 and 14, respectively, were identified in frozen berries, samples obtained throughout juice processing, and stored juices. In attempt to separate polymeric pigments, both normal phase and reverse phase TLC plates with various solvent systems were evaluated. However, only monomeric and polymeric fractions could be separated on a single plate, rather than separating each polymeric pigment by degree of polymerization. Further research is needed in order to isolate and purify polymeric pigments so that quantification methods can be developed and help explain the fate of anthocyanins during juice processing and storage.
Wilkes, K. D. (2014). Changes in Monomeric and Polymeric Pigments during Chokeberry Juice Processing. Theses and Dissertations Retrieved from https://scholarworks.uark.edu/etd/2054