(PMCA — February 9, 2022) — 2019 PMCA/Penn State Graduate Fellowship Award recipient Terianne Hamada has completed her research on the topic Effects of Alkalization on the Chemistry of Cocoa.
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Polyphenols are the most naturally abundant and well-studied group of astringent compounds. They are the main astringent components in cocoa and can be an important driving factor for the rejection of cocoa-based foods. Ongoing research suggests that proteins and pectin are some of the endogenous food components that can interact with polyphenols and mitigate the astringent response. This research has been mainly done in liquid systems such as wines, juices and simple solutions and investigation in fat-based systems like cocoa are few. Research on pectin and other cell wall polysaccharides suggests that polyphenols form complexes with these components along with proteins and Maillard reaction products. These interactions may be facilitated by processes in cocoa manufacturing such as fermentation, roasting and alkalization.
The overall objective of this study was to examine the effects of alkalization on various chemical components of cocoa that may relate to changes in the sensory properties. This study was novel in that it examined two different types of alkali (K2CO3 and NaOH) at four different levels (0, 1, 3 and 6% w/w). Properties of the cocoa analyzed included previously studied attributes such as pH and color as well as lesser studied attributes like volatile aroma compounds, polyphenols, cell wall polysaccharides, dietary fiber, and cocoa starch.
All alkalization treatments resulted in significant increases in pH and changes in color (p<0.05). Significant reductions in most volatile aroma compounds and polyphenols were observed excepting pyrazines and protocatechuic acid, which increased with alkali treatment. An increase in non-polysaccharide material was observed in cell wall isolates corresponding with an increase in soluble dietary fiber, suggesting association of pectin with polyphenols during processing. The resulting associations may be a contributing factor to the reduction of astringency in alkalized cocoa.