The use of mammalian cultured cells loaded with a fluorescent dye shows specific membrane penetration of undissociated acetic acid

Effectiveness of organic acids for inactivating pathogenic bacteria inoculated in laboratory media and foods: an updated minireview

Food processing industries commonly employ organic acids (OAAs) to determine bacterial contamination in acidified and fermented foods. OAAs are believed to possess potent antimicrobial properties by permeating cell membranes, altering proton and anion concentrations in the cytoplasm due to their lipophilic undissociated forms. The bacteriostatic or bactericidal effects of OAAs are influenced by various factors including microbial physiology, environmental pH, and acid dissociation ratios. Despite their utility, the precise mechanisms underlying OAA-mediated inhibition of pathogenic bacteria remain incompletely understood. Therefore, the objectives of this review are to compile a selected area of researches that focus on the current propensity of different OAAs for inactivating food-borne pathogens, and then to present a theoretical insight on the use of OAAs to prevent and control pathogenic bacteria present in acidic/acidified foods and their mode of mechanisms.

TRPs in taste and chemesthesis

TRP channels are expressed in taste buds, nerve fibers, and keratinocytes in the oronasal cavity. These channels play integral roles in transducing chemical stimuli, giving rise to sensations of taste, irritation, warmth, coolness, and pungency. Specifically, TRPM5 acts downstream of taste receptors in the taste transduction pathway. TRPM5 channels convert taste-evoked intracellular Ca(2+) release into membrane depolarization to trigger taste transmitter secretion. PKD2L1 is expressed in acid-sensitive (sour) taste bud cells but is unlikely to be the transducer for sour taste. TRPV1 is a receptor for pungent chemical stimuli such as capsaicin and for several irritants (chemesthesis). It is controversial whether TRPV1 is present in the taste buds and plays a direct role in taste. Instead, TRPV1 is expressed in non-gustatory sensory afferent fibers and in keratinocytes of the oronasal cavity. In many sensory fibers and epithelial cells lining the oronasal cavity, TRPA1 is also co-expressed with TRPV1. As with TRPV1, TRPA1 transduces a wide variety of irritants and, in combination with TRPV1, assures that there is a broad response to noxious chemical stimuli. Other TRP channels, including TRPM8, TRPV3, and TRPV4, play less prominent roles in chemesthesis and no known role in taste, per se. The pungency of foods and beverages is likely highly influenced by the temperature at which they are consumed, their acidity, and, for beverages, their carbonation. All these factors modulate the activity of TRP channels in taste buds and in the oronasal mucosa.