Food Engineering / Gıda Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/12
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Article Citation - WoS: 8Citation - Scopus: 7Potential Application of Hot Rehydration Alone or in Combination With Hydrogen Peroxide To Control Pectin Methylesterase Activity and Microbial Load in Cold-Stored Intermediate-Moisture Sun-Dried Figs(John Wiley and Sons Inc., 2004) Demirbüker Kavak, Dilek; Şimşek, Şebnem; Yemenicioğlu, AhmetSun-dried figs contain a considerable amount of pectin methylesterase (PME) activity (22 μM COOH/ min/g). The enzyme causes softening and loss of desired gummy texture in cold-stored intermediate-moisture (IM) sun-dried figs brought to a 28% to 29% moisture range. Partial reduction of PME activity (28%) delayed undesirable textural changes in IM figs rehydrated at 80°C for 16 min. The heat treatment did not cause a considerable reduction in microbial load. However, the addition of 2.5% H2O2 to the rehydratlon medium at 80°C reduced the initial total mesophilic aerobic count of figs by at least 90% and turned the figs from a brown color to a desirable and stable yellow-light brown. The in situ fig catalase remains after rehydration at 80°C. Thus, by reducing the contact period of figs with H2O2 or by pureeing figs, it is possible to eliminate residual H2O2 and to obtain safe and SO2-free light-colored fig products.Article Citation - WoS: 38Citation - Scopus: 43Degradation Kinetics of Anthocyanins From Sour Cherry, Pomegranate, and Strawberry Juices by Hydrogen Peroxide(John Wiley and Sons Inc., 2002) Özkan, Mehmet; Yemenicioğlu, Ahmet; Asefi, N.; Cemeroglu, BekirDegradations were studied at different hydrogen peroxide (H2O2] concentrations (9.31 to 27.92 mmol. L-1] over a range of 10 ° to 30 °C. Degradation of anthocyanins by H2O2 was described by first-order function. Comparison of t1/2 values revealed that sour cherry anthocyanins were the most resistant to H2O2, followed by pomegranate and strawberry anthocyanins. Thus, the removal of residual H2O2 from the juice contact surfaces of aseptically packaged strawberry juices should be controlled more carefully to prevent anthocyanin degradation. Respective Ea values were between 9.4 to 11.1, 9.5 to 11.4, and 11.4 to 12.2 kcal.mol-1; and Q10 values between 1.59 to 2.22, 1.62 to 2.05, and 1.76 to 2.36 for strawberry, sour cherry, and pomegranate anthocyanins.Article Citation - WoS: 8Citation - Scopus: 9Effect of Hydrogen Peroxide on Sour Cherry Anthocyanins(Hindawi Publishing Corporation, 2000) Özkan, Mehmet; Yemenicioğlu, Ahmet; Çıtak, Bahar; Cemeroğlu, BekirDegradation of sour cherry anthocyanins was studied at different H2O2 concentrations (0.233-11.63 mmol.L-1) over the temperature range of 20-55C. Degradation reaction fitted to a first order kinetic model progressed very rapidly even at low H2O2 concentrations. Thus, the t1/2 values at 20C varied between 111-20 h in the concentration range of 0.233-2.327 mmol.L-1 H2O2. The degradation of anthocyanins occurred at a faster rate with increasing temperature at 5.82 and 11.63 mmol.L-1 H2O2 concentrations. Between 25-55C, activation energies (Ea) were 9.53 and 10.60 kcal.mol-1 for 5.82 and 11.63 mmol.L-1 H2O2 concentrations, respectively. Higher Ea value at 11.63 mmol.L-1 H2O2 concentration indicated that the effect of temperature increased at higher H2O2 concentrations. A quadratic relationship (y = -0.0031x2 + 0.0218x + 0.0008, R2 = 0.996) was found between the degradation rates at 20C and H2O2 concentrations of 0.233-2.327 mmol.L-1. According to this equation, k of 1.12 × 10-3 h-1 and t1/2 of 26 days at 20C may be expected at 0.5 ppm (0.0147 mmol.L-1) H2O2 concentration, i.e., the max. allowable H2O2 level by FDA in the finished food packages.