Ascorbic acid browning, inhibition

Ascorbic acid browning is also inhibited by the addition of sulfite (Wedzicha and McWeeny, 1974). The same holds for polyphenol oxidase-catalyzed oxidation of natural phenols in fruit. The mechanism of the inhibition is by reaction of oquinone intermediates with sulfite, which leads to nonreactive sulfocatechols (Wedzicha, 1995). 

Luo Y and Barbosa-Canovas GV. 1997. Enzymatic browning and its inhibition in new apple cultivar slices using 4-hexylresorcinol in combination with ascorbic acid. Food Sci Technol Int 3 195-201. 

Browning can be controlled by adding reducing agents or acidic solutions that inhibit the activity of the PPO enzyme. Solutions of sodium bisulfite, ascorbic acid (vitamin C), and lemon juice are commonly added to freshly cut fruit to retard browning. 

L-ascorbic acid, D-isoascorbic acid, and L-dehydroascorbic acid inhibited progeny by producing diet nutritionally deficient in protein (browning)... 

Hexopar inositol nicotinate nicotinic acid, hexoprenaline [ban, inn] (hexoprenaline hydrochloride [jan]) is a P-ADRENOCEPTOR agonist selective for the P2-subtype that therapeutically can be used as a BRONCHODIIATOR in ANTIASTHMATIC treatment, hexoprenaline hydrochloride hexoprenaline. hexuronic acid ascorbic acid, hexylcaine [inn] (hexylcaine hydrochloride [usan]) is an ester series LOCAL ANAESTHETIC, used by topical application for the local relief of pain, hexylcaine hydrochloride hexylcaine. hexylresorcinol [usan] is a urinary ANTISEPTIC and an ANTHELMINTIC. It inhibits melanosis (blackspot) in shrimps, and is used as a food additive for prevention of enzymic browning in shrimps and fruits, hexyltheobromine pentifylline. 

Wedzicha, B.L. and McWeeny, D.J., Non-enzymic browning of ascorbic acid and their inhibition the production of 3-deoxy-4-sulphopentosulose in mixtures of ascorbic acid, glycine and bisulphite ion, J. Sci. Food Agric., 25, 577, 1974. 

Although the inhibition of ascorbic acid oxidation in citrus juices (22,23) and other foods by EDTA was reported by several researchers (22-24), the possibility that EDTA could inhibit non-enzymatic browning in grapefruit or other citrus juices has not been explored. 

In line with recent data on browning inhibition by thiol compounds (77), the present results indicated that the use of a variety of concentrations of L-cysteine inhibited browning (Figure 3) and reduced ascorbic acid degradation in a dose-... 

In a food system where browning is undesirable, k inhibition of the enzyme must lead to rapid inactivation of PPO. Since we have not yet found a substrate where immediate inactivation occurs, we decided to try a combination of treatments in which substrate (pyrocatechol) is added to the enzyme in the presence of ascorbic acid. The ascorbic acid acts as a reducing agent to prevent development of brown color while the enzyme is catalyzing the reaction and inactivating itself ... 

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