Inhibicion enzimatica jugo manzana

Journal of Food Engineering 62 (2004) 299–304 www.elsevier.com/locate/jfoodeng

Effect of L -cysteine, kojic acid and 4-hexylresorcinol combination on inhibition of enzymatic browning in Amasya apple juice
_ N.F. Iyidoan, A. Bayındırlı g
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Department of Food Engineering, Middle East Technical University, 06531 Ankara, Turkey Received 8 February 2003; accepted 22 June 2003

Abstract In thisstudy, the effect of different anti-browning agents on the enzymatic browning in the cloudy apple juice from Amasya cultivar was compared by considering colour changes. For this purpose, L -cysteine, kojic acid and 4-hexylresorcinol were used at different concentrations in the apple juice (0–4 mM). They were found as effective inhibitors. The combination of L -cysteine, kojic acid and4-hexylresorcinol was also studied for the control of enzymatic browning. The results showed that 89.2% inhibition was obtained at the end of 24 h storage period with the combination of 3.96 mM L -cysteine, 2.78 mM kojic acid and 2.34 mM 4-hexylresorcinol in the cloudy apple juice. L -Cysteine was found to be the most significant anti-browning agent. The interaction of kojic acid and 4-hexylresorcinol was foundto have a positive effect on the inhibition of enzymatic browning. Ó 2003 Elsevier Ltd. All rights reserved.
Keywords: Enzymatic browning; Polyphenol oxidase; Anti-browning agents; Apple juice; Response surface methodology

1. Introduction Turkey is one of the leading fruit producing countries. Starking Delicious, Golden Delicious and Amasya are the main apple cultivars grown in Turkey (Eks i, ß1997). The Amasya cultivar has a naturally low acid content (0.9–1.9 g/L) and low mass ratio of glucose to fructose (0.17–0.21). Optimum pH values for partially purified Amasya apple PPO were 7.0, 9.0, 8.6 and 6.6 on substrates catechol, 4-methyl catechol, pyrogallol and L -dopa respectively. Catechol was the most suitable substrate for Amasya apple PPO. The optimum temperature for maximum PPOactivity was 18 °C with catechol. Effectiveness of anti-browning agents on partially purified PPO increased in the order of thiourea, glutathione, beta-mercaptoethanol, sodium cyanide, ascorbic acid, sodium metabisulfide, and L -cysteine. Three PPO isoenzymes with high thermostability (as high as 80 °C) were found in Amasya apples (Oktay, K€freviolu, u g Kocacalıs kan, & Sakirolu, 1995; Yemeniciolu, gg ß ß ß € Ozkan, & Cemerolu, 1997). g

Corresponding author. Tel.: +90-312-210-5629; fax: +90-312-2101270. E-mail address: alba@metu.edu.tr (A. Bayındırlı). 0260-8774/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved. doi:10.1016/S0260-8774(03)00243-7

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Cloudy apple juice, a light, whitish-yellow juice, contains a high proportion of pulp in suspension showing a definitecloudiness. Cloudy apple juice has a growing share in the market due to its sensory and nutritional qualities. The successful process will depend on maintaining the stability of the cloud and the assurance of colour (Genovese, Elustondo, & Lozano, 1997; Tronc, Lamarche, & Maklouf, 1997). Polyphenol oxidase (PPO, o-diphenol: oxygen oxidoreductase) in the presence of oxygen catalyses two differentreactions: the hydroxylation of monophenols to o-diphenols (monophenolase/cresolase activity) and the oxidation of o-diphenols to o-quinones (diphenolase/ catecholase activity). Then quinones may condense and react non-enzymatically with other phenolic compounds, amino acids, proteins, and other cellular constituents to produce coloured polymers or pigments. Therefore, enzymatic browning have beenextensively studied in apples and apple products (Janovitz-Klapp, Richard, Goupy, & Nicolas, 1990; Martinez & Whitaker, 1995; McEvily, Iyengar, & Otwell, 1992; Nicolas, Richard-Forget, Goupy, Amiot, & Aubert, 1994; Sapers et al., 1989; Walker, 1995). The use of sulfites, a powerful anti-browning chemical, is discussed more and more because of the potential hazards. Thus, an active field of research is...