Review: Peran Enzim dalam Meningkatkan Kualitas Kopi

Indonesia is the third largest coffee producing nation in the world after Brazil and Vietnam. The types and the characteristics of Indonesian coffee are different in each area but the main important factor of consumer acceptance depends on its bitterness level. Chlorogenic acid lactone is a compounds that play an important role as contributor to the coffee bitterness that are formed during the roasting process of coffee bean because of its precursor chlorogenic acid. Chlorogenic acid is commonly found in many plants. One of them can be found in coffee with high concentration. Chlorogenic acid lactone (bitter compound) can be hydrolyzed to chlorogenic acid (non-bitter compound) using hog liver esterase and chlorogenate esterase. This study aimed to analyze the use of these enzymes to decrease the level of bitterness in coffee. The results indicated that HLE and chlorogenate esterase effectively hydrolyzed chlorogenic acid lactones in coffee. Based on the sensory test, coffee extracts treated with enzymes were less bitter than the untreated coffee extracts. If it was associated with Indonesian local coffee then the method can be done with chlorogenate esterase that was in accordance with the legal guarantee of halal product.

IP3-Independent Release of Ca2+ From Intracellular Stores: A Novel Mechanism for Transduction of Bitter Stimuli

A variety of substances with different chemical structures elicits a bitter taste. Several different transduction mechanisms underlie detection of bitter tastants; however, these have been described in detail for only a few compounds. In addition, most studies have focused on mammalian taste cells, of which only a small subset is responsive to any particular bitter compound. In contrast, ∼80% of the taste cells in the mudpuppy, Necturus maculosus, are bitter-responsive. In this study, we used Ca2+ imaging and giga-seal whole cell recording to compare the transduction of dextromethorphan (DEX), a bitter antitussive, with transduction of the well-studied bitter compound denatonium. Bath perfusion of DEX (2.5 mM) increased the intracellular Ca2+level in most taste cells. The DEX-induced Ca2+ increase was inhibited by thapsigargin, an inhibitor of Ca2+transport into intracellular stores, but not by U73122, an inhibitor of phospholipase C, or by ryanodine, an inhibitor of ryanodine-sensitive Ca2+ stores. Increasing intracellular cAMP levels with a cell-permeant cAMP analogue and a phosphodiesterase inhibitor enhanced the DEX-induced Ca2+ increase, which was inhibited partially by H89, a protein kinase A inhibitor. Electrophysiological measurements showed that DEX depolarized the membrane potential and inhibited voltage-gated Na+ and K+ currents in the presence of GDP-β-S, a blocker of G-protein activation. DEX also inhibited voltage-gated Ca2+ channels. We suggest that DEX, like quinine, depolarizes taste cells by block of voltage-gated K channels, which are localized to the apical membrane in mudpuppy. In addition, DEX causes release of Ca2+ from intracellular stores by a phospholipase C-independent mechanism. We speculate that the membrane-permeant DEX may enter taste cells and interact directly with Ca2+ stores. Comparing transduction of DEX with that of denatonium, both compounds release Ca2+ from intracellular stores. However, denatonium requires activation of phospholipase C, and the mechanism results in a hyperpolarization rather than a depolarization of the membrane potential. These data support the hypothesis that single taste receptor cells can use multiple mechanisms for transducing the same bitter compound.