Mahdi Zahedi; Zohreh Hamidi-Esfahani; Hassan Ahmadi Gavghili
Abstract
Introduction: Pectin is a structural heteropolysaccharide in the cell wall of plants and after extraction it is used as a gelling agent in food products. The main sources of pectin are apple and citrus peel, but pectin from various sources, may have unique properties. Therefore, research is ongoing to ...
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Introduction: Pectin is a structural heteropolysaccharide in the cell wall of plants and after extraction it is used as a gelling agent in food products. The main sources of pectin are apple and citrus peel, but pectin from various sources, may have unique properties. Therefore, research is ongoing to find new sources of pectin and study their properties. The conventional extracting method is performed using a solution of mineral acids, this process is time-consuming and has some disadvantages in terms of quantity and quality of extracted pectin. It is very important to look for new methods or modifications to produce pectin with high efficiency and quality. One of the new methods is ultrasonic extraction, which has been studied extensively. The aim of this study was to optimize and quantitative and qualitative evaluation of pectin extraction from tomato pomace as one of the major wastes of industries in Iran. Also Ultrasound was used as a new and effective method for extraction of pectin. Ultrasound assisted extraction (UAE) of pectin from waste tomato pomace was investigated and optimized using Box–Behnken response surface design. The individual and interactive effect of process variables (pH, temperature, extraction time and power density) on the pectin yield and purity was studied. Also, the degree of esterification, intrinsic viscosity and emulsifying properties were determined on optimized conditions.
Materials and methods: Tomato pomace was supplied from ATA Company located in Tehran, Iran. It was dried at 60 °C for 36 hours. Then was milled and sieved by 60 mesh size screen. Fatty acids and pigments were removed from tomato pomace and again dried. The obtained powder stored at ambient condition for further uses. Ultrasonic device (Ultrasonic Technology Development Company, IRAN and 400 w, 20 KHz) with 12 mm probe and double-shell tank was used to carry out the extraction. Response surface methodology (RSM) was carried out to study the effect of pH (1.5-2.5), temperature (60-90℃), extraction time (6-30 minutes), and power density (0.15-0.3 W/ml) as input variables on the yield and galacturonic acid (GalA) content as the output (responses). GalA content was determined by colorimetric method (titration), using the 3, 5- dimethylphenol as reagent and D-galacturonic acid as standard. To determine the degree of esterification, titration method was used. The intrinsic viscosity of pectin was determined by applying a capillary viscosimeter (Cannon Instruments Co., No. 150, Cannon-Fenske, Germany; k = 0.04137 mm2/s2). Emulsifying properties of pectin extracted at the optimal point were investigated at three levels of pectin concentration %0.25,% 0.5 and %1.
Results and discussion: The experimental data obtained were analyzed by analysis of variance (ANOVA) and second-order polynomial models were developed using multiple regression analysis both for pectin yield and GalA content. The models developed from the experimental design were predictive and good fit with the experimental data with high coefficient of determination (R2) value. Pectin yield and GalA content were more influenced by temperature. The highest extraction yield (10.5%) and galacturonic acid content (65%) was obtained at pH of 2, temperature of 86℃, time of 30 min, and power density of 0.3 W/ml, while in the conventional extraction method with the same extraction conditions, extraction yield of 4.5% and galactoronic acid content of 55% was obtained. According to results of this experiment, it can be concluded that main advantage of UAE is considerable shortening of extraction time with enhancement of pectin purity. Under optimal conditions, pectin with a degree of esterification 76% and intrinsic viscosity of 2.6 dl/g was obtained. The highest emulsifying activity (87.5%) was obtained at %1 concentration. By holding the emulsion at a temperature of 4°C and 23°C, the emulsion stability was significant (99%) at the concentration of %0.25 over a period of 30 days. These results showed that tomato pomace could be used as a good source of low cost pectin.
Hamed Saberian; Zohreh Hamidi-Esfahani; Hassan Ahmadi Gavghili; Mohsen Barzegar
Abstract
Introduction: Ohmic heating or direct resistance heating is one of the several electromagnetic based methods, occurs when alternating electrical current is passed through a conductive material, with the primary purpose of heating it due to the electrical resistance of the foods. There are many applications ...
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Introduction: Ohmic heating or direct resistance heating is one of the several electromagnetic based methods, occurs when alternating electrical current is passed through a conductive material, with the primary purpose of heating it due to the electrical resistance of the foods. There are many applications that can use ohmic treatment technology, such as blanching, evaporation, dehydration, fermentation, extraction, sterilization and pasteurization of foods (Saberian et al. 2015; Assiry et al. 2010). Pectins are complex heteropolysaccharides, consisting of α-1, 4-linked D-galacturonic acid units and interrupted by L-rhamnose residues with side chains of neutral sugars, mainly L-rhamnose, L-arabinose and D-galactose. In the industrial extraction process, pectin is usually extracted from waste plant material such as citrus peels, apple pomace, sugar beet pulp and sunflower head using hot water (60–100°C) acidified with a mineral acid (such as sulfuric, phosphoric, nitric, hydrochloric) or organic acid (especially citric acid) within the pH of 1.5–3 for 0.5–6 h. The aim of this study was to explore the effect of enzymatic extraction on the yield and quality properties (degree of esterification, Galacturonic acid, emulsifying properties and viscosity) of the pectin, and to compare this pectin with the pectins extracted by ohmic and conventional methods. Finally, the best extraction method was selected.
Materials and Methods: Extraction of pectin was done with the assistance of an ohmic heating system at working frequency of 50 Hz under different parameters including voltage gradient (7-15 V/cm), temperature (50-90°C), and time (5-30 min). Then, the effect of enzyme dose (0-20% v/w) of Celluclast and Rohament CL, solid/liquid ratio (S/L ratio) (1:10 to 1:50 g/ml) and extraction time (1-18 h) on the yield of the extracted pectin from orange waste was investigated.
After the time of extraction (enzymatically, ohmically or conventionally), the sample was cooled to room temperature and centrifuged (10000 rpm, 15 min), and the supernatant was precipitated with two volumes of 96% (v/v) ethanol at 4 °C for 1 h. The precipitated pectin mass was washed twice with 96% ethanol in order to remove impurities. The pectin was dried in a forced circulation oven at 55°C until a constant weight (14 h).
Galacturonic acid content was determined according to Scott (1979) with some modifications. The degree of esterification (DE) of pectin samples was determined by titrimetric method according to Santos et al. (2013).
Emulsifying activity and emulsion stability were measured according to the method described by Yapo et al. (2007).
The viscosity and the flow behavior of the selected pectin solutions (2%, w/v) extracted conventionally and ohmically at 90°C for 30 min (the optimum extraction condition) and the highest pectins extracted enzymatically, were measured at 25°C.
Pectin powder samples were mixed with KBr and pressed into KBr pellets before FTIR analysis. PerkinElmer FTIR spectra (PerkinElmer, Frontier model, USA) was applied at the transmission mode in the frequency range of 4000–400 cm-1 at a resolution of 1 cm-1.
Results were analyzed by analysis of variance (ANOVA) using SPSS 19 statistical software and the Duncan’s test with 95% confidence interval was used to compare the means of the tests. The results which were presented in this research, have been obtained from the average values of the minimal two replicate experiments.
Results and Discussion: first, the effect of enzyme dose, solid/liquid ratio (S/L ratio) and time of extraction on the yield of the extracted pectin from orange waste by using Celluclast and Rohament CL enzymes was studied. Then, the yield, of esterification, galacturonic acid, emulsifying properties and viscosity behavior of the pectins extracted in the optimum condition by enzymes were compared to the extracted pectins by ohmic and conventional methods. Results indicated that the highest yield of pectin was obtained by using Celluclast and Rohament CL enzymes at enzyme doses of 15 and 17.5%, S/L ratio of 1:20 and 1:40 (g/ml) and time of 3 h for both, which were 5.92 and 10.70 %, respectively. The highest yield of pectin by ohmic heating was obtained at the voltage gradient of 15 v/cm, the temperature of 90°C during 30 min (14.33%), which was higher than the amount obtained by conventional method (13.53%) may be due to the electroporation (disruptive pores which were made on the cell membrane by the electric field) (Cho et al., 1996). de Oliveira et al. (2015) reported that the moderate electric field (at 45°C, 50 and 100 V) extracted the pectin significantly (p < 0.05) more than the conventional extraction. The emulsifying activity of the extracted pectins by ohmic and conventional methods were 65.47 and 67.18%, respectively, although the pectins extracted by enzymatic method had not any emulsifying activity. It seems that during the pectin extraction, enzymes hydrolyzate the pectins. The viscosity of the pectins extracted by ohmic and conventional methods at the concentration of 2% was higher than those obtained from the enzymatic method. Therefore, pectin extracted by ohmic and conventional methods had the highest yield, emulsifying properties, and viscosity.
Esmaeil Zakipour-Molkabadi; Zohreh Hamidi-Esfahani; Soleiman Abbasi
Abstract
Regarding to economical importance of kiwi fruit, its wastes such as highly ripe or partially dried up fruits can be used to produce more economically valuable products like fruit leather. Therefore, the aim of present study was the effective factor evaluation of kiwi fruit leather production. The samples ...
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Regarding to economical importance of kiwi fruit, its wastes such as highly ripe or partially dried up fruits can be used to produce more economically valuable products like fruit leather. Therefore, the aim of present study was the effective factor evaluation of kiwi fruit leather production. The samples were studied in two groups, raw and cooked fruits which were treated in a boiling water bath. Defined amounts of liquid glucose (10%, 17.5%, and 25% w/w), ascorbic acid (100 mg percent of homogenized fruit) and citric acid (0%, 0.5% and 1% w/w) were added to each group. The samples were then poured in a flat pan with 7 mm thickness and were dried at 70°C in a vacuum drier to reach 14±1% moisture content. This research showed that increasing the percentage of citric acid caused an increase in fruit leather acidity whereas increasing the amount of liquid glucose caused a decrease in it. The ratio of vitamin C in samples from raw fruit was lower than that of its amount in samples prepared from cooked fruit. Furthermore, the amount of browning index in the fruit leather had a significant increase in comparison with the primary mixture before drying. Texture analysis showed that the tensile strength of the selected sample was significantly less than those of in the three other samples which are available in the market. Also, elongation of the selected sample was higher in comparison to the other samples. In the present study, regarding to the three decision variables, the acidity, the browning index and the ratio of vitamin C, six appropriate samples were selected for sensory evaluation and the most suitable sample was the sample obtained from cooked kiwi fruit which contained 25% and 0.5% of liquid glucose and citric acid, respectively.
Keywords: Kiwi fruit leather, Browning index, Vitamin C, Sensory evaluation
Soleiman Abbasi; Zohreh Hamidi-Esfahani
Abstract
Dehydration, as one of the practical ways to increase the shelf-life and applicability of yoghurt in various foodstuffs, is normally done by freeze drier (FD) which is an expensive and time-consuming process. For these reasons, in the present study the capability of microwave–vacuum drier (MVD), as ...
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Dehydration, as one of the practical ways to increase the shelf-life and applicability of yoghurt in various foodstuffs, is normally done by freeze drier (FD) which is an expensive and time-consuming process. For these reasons, in the present study the capability of microwave–vacuum drier (MVD), as an alternative process, was investigated. For doing so, the fat free yoghurt samples of 2.2, 4.2 and 6.2 mm were dehydrated under various combination of absolute pressures (60, 200, 400, 600, and 800 mbar) and microwave powers (35,130, and 260 W) using a lab scale drier designed in our lab. Based on our findings, the drying time of yoghurt in microwave–vacuum drier for thickness of 2.2 mm was considerably (80%) shorter than commercial freeze-drier. In addition, the dependency of the drying time to absolute pressure was much less than microwave power and yoghurt thickness. Furthermore, except the color and bulk density, the rest of the qualitative parameters of yoghurt powders dehydrated by MVD and FD methods were almost similar. It should be noted that the highest resemblance in terms of quality and color indices between FD and MVD powders was seen at combination of low microwave power and low absolute pressure (35 W, 60 mbar). All in all, the findings of this study showed the capability of MVD for production of yoghurt and other food powders and this technique can be introduced as a potential alternative for FD.
Keywords: Yoghurt, Shelf-life, Microwave, Drying, Quality
