Elektrik potansiyeli ve sıcaklığın ohmik ısıtma ve sıcak suya daldırma esnasında makarnaların rehidrasyon davranışları üzerine etkisi

In the present study, rehydration of pasta samples was examined during soaking at different temperatures (75, 85 and 95°C) and during ohmic heating at different electrical potential levels (10, 20, 30 and 40 V/cm) as an alternative method of pasta cooking. Two effective diffusion coefficients were defined using Fick’s second law of diffusion for regular soaking experiments and three diffusion coefficients were calculated to describe the rehydration behaviour during ohmic heating. The effect of applied voltage and temperature on the diffusion coefficients were evaluated using an Arrhenius type equation. Moreover, the two common models that are used to describe rehydration behaviour of food materials, namely Peleg and Weibull models, were used for kinetic analysis of rehydration experiments. It was observed that an increment both in temperature of cooking water and applied voltage for ohmic heating enhanced the water absorption rate of pasta samples then the rehydration was completed faster. The Peleg and Weibull models showed promising performance for regular soaking experiments where the first one could not describe moisture change of pasta during ohmic heating at a desired level. Different from soaking testes, a delayed moisture uptake phase was observed at the very beginning of ohmic heating experiments however it can be concluded that ohmic heating led an increment in moisture uptake rate in general.Söz konusu çalışma kapsamında, farklı elektrik potansiyelleri altında (10, 20, 30 ve 40 V/cm) ohmik ısıtma ve farklı sıcaklıklarda (75, 85 ve 95°C) suya daldırma işlemi esnasında makarna örneklerinin rehidrasyon özellikleri incelenmiştir. Makarnaların rehidrasyon davranışlarını ifade etmek için Fick’in ikinci difüzyon kanunu kullanılarak, normal daldırma denemeleri için iki ve ohmik ısıtma denemeleri için üç farklı efektif difüzyon katsayısı hesaplanmıştır. Uygulanan farklı voltaj ve sıcaklıkların difüzyon katsayıları üzerine etkisi ise Arrhenius tipi bir eşitlikte değerlendirilmiştir. Ayrıca, gıdaların rehidrasyon özelliklerinin tanımlanmasında yaygın olarak tercih edilen iki model, Peleg ve Weibull, rehidrasyon denemelerinin kinetik analizi amacıyla kullanılmıştır. Elde edilen veriler neticesinde, hem daldırma suyu sıcaklığının hem de ohmik ısıtma esnasında uygulanan voltajın artırılması, makarna örneklerinin su emilimini hızlandırıcı etki göstermiştir. Hem Peleg hem de Weibull modelleri, normal daldırma denemeleri için üst düzey bir performans ortaya koymuştur. Ancak bunlardan sadece Weibull, ohmik ısıtma esnasında gözlenen nem değişimini kabul edilebilir seviyede ifade edebilmiştir. Normal daldırma denemelerinden farklı olarak, ohmik ısıtma işleminin ilk safhalarında nem emiliminde bir gecikme dikkati çekmiştir. Ancak genel olarak ohmik ısıtmanın makarnaların nem absorpsiyonu üzerine hızlandırıcı bir etkiye sahip olduğu ifade edilebilir

Üzüm suyu filtrasyonu, berrak meyve sularının termofiziksel özellikleri ve üzüm asma dalından polifenolik bileşiklerin basınçlanmış düşük polariteli su (bdps) ile özütlenmesi.

In this study it was aimed to design and operate a new system with sufficient number of rotating drums since rotation of turntable is incapable of providing uniformity. Effect of new design on final color values and moisture content were also investigated. Macaroni beads were colored with CoCl2 solution and processed in a domestic microwave oven starting from 11.3±0.10% moisture content and L*= 41.1±0.31 , a*= 8.5±0.27 , b*= 5.3±0.22 color value with turntable and the proposed design. In experiments 40%, 60%, 80% and 100% power levels and 1, 2 and 3 min processing times and 2 different locations were used. The average color values measured were not affected significantly by the locations studied inside the cavity for both operation types. The changes in color values were found to be significant with altering power level for both operation types. Time also changed average color values for samples processed on turntable and in rotating drums. The new design lowered the average L* values of the final product and kept the sample from burning. Average a* and b* values were not significantly affected by the operation type. The uniformity of final product in terms of color distribution was affected significantly by the operation type and the improvement in uniformity calculated quantitatively by means of variances and found out that the new design improved the color uniformity of the final product by 94.7%. The non-uniformity of the products processed on turntable was significantly changed with power level. Time or location did not affect uniformity significantly for both operation types. The final average moisture contents of samples processed on turntable were lower than the ones processed with the new design. That is, the rotating drums lowered the moisture removal compared to the turntable.Ph.D. - Doctoral Progra

Evaluation of Two Fitting Methods Applied for Thin-Layer Drying of Cape Gooseberry Fruits

ABSTRACT Drying data of cape gooseberry was used to compare two fitting methods: namely 2-step and 1-step methods. Literature data was also used to confirm the results. To demonstrate the applicability of these methods, two primary models (Page, Two-term-exponential) were selected. Linear equation was used as secondary model. As well-known from the previous modelling studies on drying, 2-step method required at least two regressions: One is primary model and one is secondary (if you have only one environmental condition such as temperature). On the other hand, one regression was enough for 1-step method. Although previous studies on kinetic modelling of drying of foods were based on 2-step method, this study indicated that 1-step method may also be a good alternative with some advantages such as drawing an informative figure and reducing time of calculations

Optimisation of antioxidant activity of grape cane extracts using response surface methodology

Solid-liquid extraction and response surface methodology were used to optimise conditions for the antioxidant activity of grape cane extracts. The independent processing variables were ethanol concentration, temperature and solvent to solid ratio. Ethanol concentration and temperature significantly affected antioxidant activity measured by the Trolox equivalent antioxidant capacity (TEAC) assay and the oxygen radical absorbance capacity using fluorescein (ORAC(FL)) method (p 0.05). Antioxidant activity of the extracts, determined by the TEAC assay, varied from 85.6 to 238.6 mu mol Trolox equivalents/g of dry sample. ORAC(FL) values ranged from 308.4 to 1302.7 mu mol Trolox equivalents/g of dry sample. Ethanol concentrations of 40.4% and 55.4% were optimal for the highest antioxidant activities measured by the TEAC assay and the ORAC(FL) method, respectively. The optimal temperature was 83.6 degrees C. Antioxidant activity correlates with total phenolic content of extracts. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved

Optimization of solid-liquid extraction of resveratrol and other phenolic compounds from milled grape canes (Vitis vinifera)

Optimization of the solid-liquid extraction conditions for trans-resveratrol, trans-E-viniferin, ferulic acid, and total phenolics from milled grape canes has been investigated. The temperature and ethanol concentration were found to be major process variables for all responses, whereas the solvent to solid ratio was found not to be significant for any of the responses studied. The yields of transresveratrol, trans-epsilon-viniferin, and total phenolics increased with increasing temperature. Maximum yields of trans-resveratrol (4.25 mg/g dw), trans-epsilon-viniferin (2.03 mg/g), and total phenolics (9.28 mg/g dw) were predicted from the combination of a moderate ethanol concentration (50-70%) and the highest temperature (83.6 degrees C), whereas an ethanol concentration of 35% at the lowest temperature studied (16.4 degrees C) was optimal for the extraction of ferulic acid (1.05 mg/g dw). Effective diffusivity values of resveratrol in the solid phase, D(eff) for different extraction conditions, were calculated by fitting the experimental results to a model derived from the Fick's second law. Effective diffusivity of resveratrol in the solid phase varied from 3.1 x 10(-13) to 26.6 x 10(-13) m(2) s(-1) with changing extraction conditions. The increase in effective diffusivity of resveratrol was observed with increasing temperature, and the highest predicted level was obtained when using 54% ethanol/water mixture at 83.6 degrees C. The increase in ethanol concentration exhibited the favorable effect up to 50-55%, thereafter effective diffusivity decreased with a further increase in concentration

Optimization of Solid−Liquid Extraction of Resveratrol and Other Phenolic Compounds from Milled Grape Canes ( Vitis vinifera

Optimization of the solid-liquid extraction conditions for trans-resveratrol, trans-E-viniferin, ferulic acid, and total phenolics from milled grape canes has been investigated. The temperature and ethanol concentration were found to be major process variables for all responses, whereas the solvent to solid ratio was found not to be significant for any of the responses studied. The yields of transresveratrol, trans-epsilon-viniferin, and total phenolics increased with increasing temperature. Maximum yields of trans-resveratrol (4.25 mg/g dw), trans-epsilon-viniferin (2.03 mg/g), and total phenolics (9.28 mg/g dw) were predicted from the combination of a moderate ethanol concentration (50-70%) and the highest temperature (83.6 degrees C), whereas an ethanol concentration of 35% at the lowest temperature studied (16.4 degrees C) was optimal for the extraction of ferulic acid (1.05 mg/g dw). Effective diffusivity values of resveratrol in the solid phase, D(eff) for different extraction conditions, were calculated by fitting the experimental results to a model derived from the Fick's second law. Effective diffusivity of resveratrol in the solid phase varied from 3.1 x 10(-13) to 26.6 x 10(-13) m(2) s(-1) with changing extraction conditions. The increase in effective diffusivity of resveratrol was observed with increasing temperature, and the highest predicted level was obtained when using 54% ethanol/water mixture at 83.6 degrees C. The increase in ethanol concentration exhibited the favorable effect up to 50-55%, thereafter effective diffusivity decreased with a further increase in concentration

CHANGES IN TOTAL PHENOLIC AND FLAVONOID CONTENTS OF ROWANBERRY FRUIT DURING POSTHARVEST STORAGE

Postharvest storage conditions of rowanberry (Sorbus aucuparia) fruits were investigated. The influences of temperature and storage time on total phenolic content were observed. Both variables affected phenolic content of rowanberries, and their total phenolic contents significantly reduced during the 20-day storage at 4 and 22C. The loss of total phenolic was found to be almost 50% of its initial amount (3,619.8 mg/kg fresh weight [fw]) at 22C, which was higher than occurred loss (30%) at 4C. An investigation of rowanberry flavonoids showed the presence of rutin, quercetin-3-glucoside and quercetin-3-D-galactoside (Q3DG). Quantitative analysis of berry flavonoids showed Q3DG as a major compound, being 24.55 mg/kg fw. The highest reduction (86% of its initial amount) was also seen in that compound level compared with other ones. Degradation kinetics of flavonoids was studied at 22C over 16 days of storage. Checking of model adequacies indicated that their reductions followed a first-order kinetic

Grape cane waste as a source of trans-resveratrol and trans-viniferin: High-value phytochemicals with medicinal and anti-phytopathogenic applications

Grape cane waste was investigated as a potential source of high-value phytochemicals with medicinal and anti-phytopathogenic applications. Extraction yields of trans-resveratrol and trans-epsilon-viniferin from Vitis vinifera cv. Pinot Noir grape cane were 3.45 +/- 0.04 and 1.30 +/- 0.07 mg g(-1) dw, respectively. The analyte extraction efficiencies were investigated using protic and aprotic solvents. Yields varied 22-fold over the range of solvent systems investigated, demonstrating the importance in solvent polarity and hydrogen bonding capability for efficient extractions. The current study suggests that these compounds can be quantitatively extracted from grape cane residue using low-cost, environmentally benign, and non-toxic aqueous alcoholic solvent systems such as ethanol:water mixtures. With current commercial values of trans-resveratrol and trans-epsilon-viniferin between US$2000 and US$ 3000 per kg, established stilbene yields from cane waste could represent an agricultural coproduct valued at US$2000-US$ 3000 per hectare of production. At present levels of worldwide wine grape production, the extraction of trans-resvertrol and trans-epsilon-viniferin from grape cane waste may reach a global economic value of >$30 billion. (c) 2007 Published by Elsevier B.V