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    Clarification and the concentration of apple juice using membrane processes: A comparative quality assessment
    (2010) Onsekizoğlu, Pelin; Bahçeci, Kazım Savaş; Acar, Jale
    The aim of this study was to evaluate the potential of integrated membrane processes for the clarification and the concentration of apple juice, taking into account the impact on the product quality. The fresh apple juice, with a total soluble solids (TSS) content of about 12°Brix was previously clarified by combined application of fining agents (gelatin and bentonite) and ultrafiltration (UF) through 10 kDa or 100 kDa molecular weight cut-off (MWCO) membranes on laboratory scale. The clarified juice was then concentrated by osmotic distillation (OD), membrane distillation (MD), coupled operation of OD and MD or by conventional thermal evaporation up to 65°Brix. The effect of different clarification and concentration processes on formation of 5-hydroxymethylfurfural (HMF), retention of bioactive compounds (phenolic compounds, organic acids, glucose, fructose and sucrose) and their efficiency in preserving natural color and aroma (trans-2-hexenal, the most relevant compound in apple juice aroma) were evaluated in order to maintain a high quality product. The new membrane-based concentration techniques were very efficient since the product characteristics were very similar to that of the initial apple juice especially regarding the retention of bright natural color and pleasant aroma, which are significantly lost during thermal evaporation. Furthermore, among all the concentration treatments applied, only thermally evaporated samples resulted formation of HMF. Phenolic compounds, organic acids and sugars were very stable against all concentration processes, including thermal evaporation. Coupled operation of OD and MD reduced trans-2-hexenal losses drastically tending towards that of the initial juice and hence can be proposed as the most promising alternative to conventional thermal evaporation technique. © 2010 Elsevier B.V. All rights reserved.
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    The effects of ascorbic and cinnamic acid addition and different pasteurization parameters on the inactivation of alicyclobacillus acidoterrestris in apple juice
    (2011) Sarıtaş, Ayşe Nur; Bahçeci, Kazım Savaş; Acar, Jale
    In this study, thermal inactivation parameters (z-, F- and D-values) of Alicyclobacillus acidoterrestris DSM 2498 strain, is an acidophilic, spore-forming microorganism that can survive typical pasteurization conditions, and may spoil fruit juices by producing off-flavour, were determined in clear apple juice and cloudy apple nectar. The effects of ascorbic acid and cinnamic acid at different consantrations (250 and 500 mg/L) on thermal inactivation of A. acidoterrestris were also investigated. When acid consantrations used in research was increased a decline in the z-value of A. acidoterrestris was observed. It was determined that decrease in z-values were greater in the clear apple juice than apple nectar. The reason of this difference is thought to be the protective effect of particulles in the apple nectar. D-values of A. acidoterrestris in clear apple juice were determined between D 93°C 7.3 min. and D 99°C 1.5 min, while in apple nectar this values were changed between D 93°C 7.7 min. and D 99°C 1.9 min. z-values obtained from D values were compared with z-values which were found experimentally before and almost close results were detected. In the last part of study, 10 6 CFU/mL of A. acidoterrestris spores were added into clear apple juice samples which prepared from commercial concentrated apple juice and pasteurized at 96°C according to the thermal death times determined before. Afterwards pasteurized samples stored at refrigerator temperature (+4°C) for 0, 5 and 10 days and at room temperature (-20°C) for 1, 2, and 3 months. At the end of the storage period microbiological analyzes of clear apple juice samples were carried out by using membran filtration method. No bacterial development was observed in samples stored in case of three analogous. This result showed that adequate lethality was obtained using F-values which determined before at different times for 96°C.
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    The use of factorial design for modeling membrane distillation
    (2010) Onsekizoğlu, Pelin; Bahçeci, Kazım Savaş; Acar, Jale
    A two-level factorial experimental design was used to investigate the influence of the main operating parameters on evaporation flux and soluble solid content of apple juice during concentration through osmotic distillation (OD) and membrane distillation (MD) processes. The factorial models have been obtained from experimental design to study all interactions among the considered parameters (osmotic agent concentration (0-65% CaCl2), flow rate (10-30 L/h) and temperature difference between feed and osmotic agent (10-30 °C)) and validated statistically by analysis of variance (ANOVA). For both responses, the osmotic agent concentration was the most influential factor. The magnitude of the main influence of CaCl2 concentration was followed by the temperature difference and flow rate, respectively. The analysis of the experimental responses revealed that CaCl2 concentration and temperature difference had significant interactive effects on evaporation flux. All interactions between the studied parameters were significant in the case of soluble solid content at the 99% confidence level. Although the interaction terms have significant effects, their levels were only a small amount compared to linear effects. The predicted responses were compared with the experimental ones. In general, the predicted values were in reasonable agreement with the experimental data, further confirming the very good prediction ability of the models. © 2009 Elsevier B.V. All rights reserved.