پديد آورندگان :
گنجلو، علي دانشگاه زنجان - دانشكده كشاورزي - گروه علوم و مهندسي صنايع غذايي , بي مكر، ماندانا دانشگاه زنجان - دانشكده كشاورزي - گروه علوم و مهندسي صنايع غذايي , قرباني، مسعود دانشگاه زنجان - دانشكده كشاورزي - گروه علوم و مهندسي صنايع غذايي
كليدواژه :
استخراج , تركيبات فنولي , سينتيك انتقال جرم , غلاف نخود فرنگي , فعاليت ضد راديكالي
چكيده لاتين :
Introduction: Agriculture is regarded as one of the most important fields of human industry, due to its role in ensuring global food security for people around the world and supporting other industries. Agricultural processing industries create a great amount of residues/byproducts, which are considered as “wastes”. The green pea (Pisum sativum L.) is one of the most important legumes in the world which its pod is considered a biological waste and discarded (Amarowicz and Troszyñska 2003). Interestingly, agricultural wastes contain many valuable bioactive compounds, possessing a wide range of potential pharmacological properties, which have great contributions to make in related industries, such as nutraceuticals or functional foods, medicines, pharmaceuticals and cosmetics. However, they are still underutilized as abundant, inexpensive, renewable and sustainable sources of natural bioactive compounds. Phenolic compounds are a large class of plant secondary metabolites that exhibit multiple biological activities (Diouf et al. 2009). Thus, phenolic compounds recovery from the low-cost resources has become increasingly important in recent years. Extraction is a key step in the way of valuable bioactive compounds preparation which greatly influenced by several parameters (Samavati and Manoochehrizade 2013). Extraction method, solvent type, solvent pH, temperature, extraction time, raw material to solvent ratio, raw material particle size and different pretreatments have a significant effect on the efficiency of valuable bioactive compounds extraction process (Chirinos et al. 2007). Knowledge on the kinetics of mass transfer during the extraction process is required for adequate control and the correct operational design. Different empirical and semi-empirical models such as Pseudo-first order, film Theory, Minchev and Minkov, Peleg, nth order, and Weibull presented to predict the kinetics of mass transfer without taking into account the underlying phenomena. These models represent data at conditions similar to those upon which such models were developed. However, far too little attention has been paid to study the kinetics of bioactive compounds extraction from agricultural wastes/byproducts. Thus, the present study was designed to determine the effect of different drying methods and type of solvent on the kinetics of phenolic compounds extraction from green pea pods. Finally, the antiradical activities of green pea pods extracts containing phenolic compounds were determined.
Material and methods: The green pea pods were washed and dried using different drying methods including shade, hot air (50 and 70 ºC), and freeze-drying to the final moisture content of 9.5%±0.22. Dried pods were grounded and pass through a 35-mesh sieve to produce homogenous dried green pea pod powder. Phenolic compounds were extracted from green pea pods through maceration technique using different solvents including water, acetone, ethanol and n-hexane. The sample to solvent ratio, temperature and extraction time was 1:20 (w/w), 25 ºC, and 1440 min, respectively. Total phenolic content (TPC) of extracts was determined using the Folin–Ciocalteu method, based on the colorimetric reaction of the sample with the Folin–Ciocalteu reagent and reported as a milligram equivalent gallic acid per gram of sample (mg GAE/g) (Amin et al. 2004). The antiradical activities of phenolic extracts were measured using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydrogen peroxide (H2O2) methods. Different empirical models including nth order, Peleg and Weibull were used for fitting experimental data using non-linear regression through Gauss–Newton method. The quality of the fit between the experimental and predicted data was determined according to values of correlation coefficient (R2), the root mean square error (RMSE), and the mean relative percentage deviation modulus (E). The best model was chosen as one with the highest R2 and the least RMSE and E values.
Results and discussion: The results revealed that drying method and solvent type have a significant effect (P<0.05) on phenolic compounds extraction. The amount of phenolic compounds under different conditions was in the range of 0.24-14.44 mg GAE/g. The highest amount of phenolic compounds was obtained using freeze-drying and ethanol as solvent equivalent to 14.44 ± 0.27 mg GAE/g. While the lowest total phenolic content (0.22 ± 0.02 mg GAE/g) was related to the hot air dried (70 °C) green pea pods treated with n-hexane as solvent. The experimental data fitted well with Peleg model considering maximum correlation coefficient (0.9908-0.9979), minimum root mean square error (0.001-0.140) and mean relative percentage deviation modulus (3.443-9.704). Based on the Peleg model, Peleg rate constant (K1), Peleg capacity constant (K2) and equilibrium of phenolic compounds (Ceq) were estimated. The lower Peleg rate constant described the higher initial mass transfer rate. The minimum Peleg rate constant was obtained for the dried samples by freeze drying and using ethanol as solvent. The lower Peleg capacity constant also represented the higher equilibrium content. Similar trend have been also observed for Peleg capacity constant. The equilibrium point (Ceq) is reached when phenolic content of matrix and solvent become equal. The high correlation coefficient (R2=0.991) was found between experimental values and predicted values by the Peleg model confirmed the precision of the Peleg model for estimation of the phenolic compounds extracted from green pea pods. Antiradical activity assessment of green pea pod phenolic extracts showed the high capacity for inhibiting DPPH (up to 48.85%) and hydrogen peroxide (up to 14.51%) free radicals. The highest antiradical activity of phenolic compounds was related to the green pea pods which treated by freeze-drying method and ethanol as solvent whereas the lowest antiradical activity was obtained for air-dried samples at 70 ºC and n-hexane as extraction solvent. A linear relationship with the high correlation coefficient
(R2=0.70-0.80) was found between the total phenolic content and the free radicals inhibitory activity.
Conclusion: The current study found that drying methods and solvent types have a significant effect (P>0.05) on the extraction of phenolic compounds from green pea pods. The highest amount of phenolic compounds was extracted from green pea pods by using freeze-drying and ethanol as solvent. In addition, the Peleg model can be used to study the kinetics of mass transfer during phenolic compounds extraction. As a result, green pea pod can be introduced as a low-cost source for the extraction of phenolic compounds. This finding has important application for developing natural ingredients to be used in the food and pharmaceutical industries.
