比较不同浓缩蛋白的功能特性.pdf

Comparative studies on the functional properties of various protein concentrate preparations of peanut protein Haiwen Wu a Qiang Wanga Tiezheng Maa Jiajia Renb aInstitute of Agro food Science and Technology The Key Laboratory of Agro food Process and Quality Control Ministry of Agriculture Chinese Academy of Agricultural Sciences No 2 Yuanmingyuan West Road Haidian District Beijing 100193 PR China bOil and Fat Equipments Research Institute Chinese Academy of Agricultural Mechanization Sciences No 1 Beishatan Road Chaoyang District Beijing 100083 PR China a r t i c l ei n f o Article history Received 21 October 2008 Accepted 14 December 2008 Keywords Different preparations Peanut protein Functional properties a b s t r a c t The effect of different preparations on the functional properties of peanut protein concentrates was stud ied Peanut protein concentrates were isolated from defatted peanut fl our by isoelectric precipitation alcohol precipitation isoelectric precipitation combined with alcohol precipitation alkali solution with isoelectric precipitation and their functional properties protein solubility water holding oil binding capacity emulsifying capacity and stability foaming capacity and rheology were evaluated The results showed that the protein solubility foaming capacity and stability of protein prepared by alkali solution with isoelectric precipitation were the best of all the peanut protein products But the protein prepared by alcohol precipitation had better water holding oil binding capacity which was signifi cantly different from other protein products The emulsifying stability of protein concentrate prepared by different meth ods was signifi cantly lower than that of defatted protein fl our The protein prepared by isoelectric precip itation and isoelectric precipitation combined with alcohol precipitation had better gel properties which indicated that they were a potential food ingredient Crown Copyright 2008 Published by Elsevier Ltd All rights reserved 1 Introduction The peanut Arachis hypogaea L is an important crop grown in China and worldwide The total yield in China has been the highest in the world since 1993 In 2007 Chinese export of peanut was about 637 4 million kilogram Peanut web of China 2008 Most peanuts grown in China are primarily used to produce edible oil The remaining meal also called as defatted peanut fl our DPF is a protein rich inexpensive and underutilized by product of the peanut industry which contains 50 55 high quality protein DPF despite having an excellent amino acid profi le has found only marginal use in food industry due to its inferior functional proper ties Beuchat Cherry Yu Ahmedna Fuhrmeister Yumiko Yoshiko Michael Yu et al 2007 2 2 1 Isoelectric precipitation To produce test PPC defatted peanut fl our was mixed with water at the ratio of 1 10 w v The mixture was stired at room temperature for 1 h then adjusted to pH 4 5 the isoelectric pH as determined in Section 3 2 with 1 0 N hydrochloric acid HCl The suspension was then centrifuged at 3500g for 20 min The supernatant was discarded and the precipitate involved re sus pensed in water at the ratio of 1 10 and stired at room temperature for 1 h in order to clear acid then centrifuged at 3500g for 20 min The precipitate was collected and dried using a LGJ 25 freeze dryer Sihuan science instrument factory Beijing The dry PPC powder was stored in a refrigerator until use in functionality tests 2 2 2 Aqueous precipitation Defatted peanut fl our was mixed with aqueous alcohol 75 at fl our aqueous alcohol ratio of 1 10 leaching time min and tem perature C of 60 min and 30 C respectively and centrifuging the suspension at 1500g for 10 min Then the supernatant was dis carded and the precipitate involved re suspensed in aqueous alco hol 85 at the ratio of 1 8 leaching time min and temperature C of 30 min and 35 C and the suspension was centrifuged as de scribed in the fi rst recovery test and dried as described in Section 2 2 1 2 2 3 Isoelectric precipitation and alcohol precipitation Defatted peanut fl our was employed using isoelectric precipita tion pH 4 5 and centrifugation separations as described in Section 2 2 1 The precipitates involved re suspension in aqueous alcohol 85 at the ratio of 1 10 and stired at room temperature for 30 min then centrifuged at 3500g for 20 min and dried as de scribed in Section 2 2 1 2 2 4 Alkali solution and isoelectric precipitation Deffated peanut fl our was mixed with water at fl our to water ratios of 1 10 and a solubilization pH of 8 5 adjusted with 1 0 N NaOH The peanut fl our suspensions were stired at room tempera ture for 1 h then centrifuged at 3500g for 20 min The supernatants were collected and adjusted to pH 4 5 the isoelectric pH as deter mined in Section 3 2 with 1 0 N HCl The suspensions were centri fuged at 3500g for 20 min The supernatants were discarded and the precipitate was dried as described in Section 2 2 1 2 3 Preparation of peanut protein gels The peanut protein products were dispersed with phosphate buffer pH 7 0 at protein buffer ratio of 12 100 w v The disper sions were stired at room temperature for 120 min Twenty milli liters of each suspension was put into a beaker sealed with a fi lm and heated at 90 C for 60 min followed by immediate cool ing in a bath of cold water The heated samples were stored at 4 C for 14 h until tested 2 4 Proximate composition analysis Total protein content of deffated peanut fl our and peanut pro tein concentrates was evaluated using a FOSS nitrogen analyzer and a conversion factor of 6 25 Fat moisture ash and crude fi bre contents were determined using standard AOAC methods 932 06 925 09 923 03 and 994 13 respectively AOAC 1990 Carbohy drate content was determined using AOAC 1996 2 5 Determination of functional properties 2 5 1 Protein solubility Peanut protein products were mixed with water at the ratio of 1 100 w v and pH of the mixtures adjusted to 2 0 12 0 with 1 0 N NaOH and HCl The suspensions were stirred at room temper ature for 1 h and then centrifuged at 3000g for 20 min Protein concentration in each supernatant was determined by kjeldahl method AOAC 1996 by a FOSS Nitrogen Analyzer 2300 Foss Cor poration Sweden using 6 25 as the conversion factor Triplicate determinations were carried out and the solubility profi le was ob tained by plotting averages of protein solubility against pH Protein solubility was calculated as solubility W1 W0 where W1was the weight of amount of protein in the supernatant g W0was the weight of amount of protein in the sample g 2 5 2 Water holding capacities Water holding capacity was determined by using the method outlined by Beuchat 1977 One gram of peanut fl our or protein concentrate was weighed into a pre weighed 15 ml centrifuge tube For each sample 10 ml of distilled water was added and mixed using a Fisher Gene II vortex at the highest speed for 2 min After the mixture was thoroughly wetted samples were al lowed to stand at room temperature for 30 min then centrifuged at 3000g for 20 min The supernatant was decanted and the centri fuge tube containing the sediment was weighed Water holding capacity grams of water per gram of protein was calculated as WHC W2 W1 W0 where W0was the weight of the dry sample g W1was the weight of the tube plus the dry sample g and W2 was the weight of the tube plus the sediment g Triplicate sam ples were analyzed for each protein concentrate 2 5 3 Oil binding capacities The oil binding capacity was determined using the method of Chakraborty 1986 One gram W0 of protein was weighed into pre weighed 15 ml centrifuge tubes and thoroughly mixed with 10 ml V1 of vegetable oil soybean oil using a Vortex mixer 344H Wu et al Food Research International 42 2009 343 348 Samples were allowed to stand for 30 min The protein oil mix tures were centrifuged at 3000g Feige Centrifuge 4500 R for 20 min Immediately after centrifugation the supernatants were carefully poured into a 10 ml graduated cylinder and the volumes were recorded V2 The oil binding capacity milliliter of oil per gram of protein was calculated as OBC V1 V2 W0 Triplicate samples were analyzed for each fl our protein concentrate 2 5 4 Emulsifying activity and stability EA ES The emulsifying activities were determined by the method of Pearce and Kinsella 1978 with slight modifi cations Emulsifying activities at protein concentration of 0 5 w v in Britton Robin son buffer were examined at pH values of 2 0 12 0 The dispersions 40 ml were pre homogenized using FLUKO homogenizers at 10 000g for 30 s and then 40 ml of peanut oil was added to each protein suspension followed by homogenization at 10 000g for 2 min Forty microlitres of emulsion avoidance of the supernatant foam were removed carefully by micropipettor from the emul sions and immediately mixed with 10 ml of 0 1 SDS solution and the absorbance of the mixture E0 which showed the emulsi fying capacity EC was determined at 500 nm Ten minutes later another 40ll of emulsion were removed from the emulsions as stated above and immediately mixed with 10 ml of 0 1 SDS solu tion again and the absorbance of the mixture Et which showed the emulsifying stability min t was 10 min was determined at 500 nm Emulsifying stability was calculated using the formula ES E0 t E0 Et Triplicate samples were analyzed for each fl our protein concentrate 2 5 5 Foaming capacity The foaming capacity FC was determined in triplicate using the method described by Makri Papalamprou and Doxastakis 2005 with slight modifi cations Concentrations of 1 fl our were prepared in de ionized water and adjusted to pH 7 4 with 1 0 N NaOH and 1 0 N HCl Volumes of 100 ml V1 of peanut protein con centrate suspension was blended for 3 min using a high speed blender poured into 250 ml graduated cylinders and the volume of foam Vt were immediately recorded at 0 min 30 min and 60 min FCwascalculatedusingthefollowingequation FC Vt V1 100 100 2 5 6 Texture profi le analysis TPA of the gels To evaluate the texture of peanut protein gels a uniaxial com pression test was performed with a TA TX2i Texture Analyzer Sta ble Micro Systems Ltd Godalming England The method of O Kane Happe Vareijken Gruppen this development reduced the repulsive forces acting among the protein molecules creating an identical situation as for the isoelectric region whereas further increase in ionic strength infl uenced the gel forming process negatively by decreas ing the protein unfolding Similar observations had been reported for whey protein and pea protein Boye Alli Ismail Gibbs Shand Ya Pietrasik Wanasundara 2007 The results Table 2 Effect of pH on emulsifying stability min of peanut protein products SamplepH 2 04 56 08 010 012 0 DPF50 68 1 55c43 36 1 57d54 04 3 21c60 04 0 62b64 94 0 70a31 72 1 38e IPPPC37 80 1 01a18 92 1 45d29 95 0 65bc32 58 0 49b33 54 3 19b20 46 0 64c AAPPC34 50 1 18a29 37 2 77c27 58 1 59d34 49 1 26a34 10 0 23a32 19 1 25b IAPPC56 43 3 57a34 44 1 48b39 02 3 20b39 49 0 81b39 77 0 06b35 27 5 48b PPI16 71 0 40c14 89 0 19d19 18 0 48b20 45 0 19b24 31 1 34a20 36 0 39b All values are means of triplicate determinations standard deviation Means within lines with different letter a b c d or e are signifi cantly different p 0 05 0 10 20 30 40 50 60 DPF Peanut Protein Products Foaming Capacity Volume of Foam at 0min Volume of Foam at 30min Volume of Foam at 60min PPIIAPPCAAPPCIPPPC Fig 4 Foaming capacity FC of peanut protein products defatted peanut fl our DPF isoelectric precipitation peanut protein concentrate IPPPC aqueous alcohol bis leach peanut protein concentrate AAPPC isoelectric precipitation and aqueous alcohol leach peanut protein concentrate IAPPC peanut protein isolate PPI Table 3 Texture profi le analysis TPA of peanut protein gels SampleRheological testing Hardness g SpringinessCohesiveness DPF56 70 2 80b0 90 0 02a0 56 0 01bc IPPPC64 96 2 93a0 86 0 03a0 52 0 02a AAPPC57 47 0 58b0 90 0 03a0 53 0 02ab IAPPC69 46 3 98a0 88 0 03a0 51 0 02b PPI16 43 0 50c0 58 0 02b0 48 0 01c All values are means of triplicate determinations standard deviation Means within columns with different letter a b or c are signifi cantly different p 0 05 H Wu et al Food Research International 42 2009 343 348347 of rheological testing of DPF IPPPC AAPPC and IAPPC when com pared with testing of common gel based foods such as hard tofu soft tofu bologna and egg white Pinterits Arntfi eld 2007 showed that peanut protein products were a potential food ingredient 4 Conclusions Peanut protein concentrate IPPPC AAPPC IAPPC and PPI pre pared by different methods had varied functional properties such as solubility water holding oil binding capacity foaming capacity emulsifying capacity and stability and rheological properties The study determined that the functional properties such as solubility foaming capacity and stability of protein prepared by alkali solu tion and isoelectric precipitation were the best compared to that of other peanut protein products It could be suitable for food sys tems requiring foaming such as cake and ice cream The protein prepared by alcohol precipitation had better functional properties particularly water holding oil binding capacity which were signif icantly different from other protein products It could be effectively used for making protein concentrates and suitable for use in vari ous food formulations such as weaning foods dry mixes baked foods whipped toppings and salad dressings owing to its high water and oil binding capacities The emulsifying stability of pro tein concentrate prepared by different methods were signifi cantly lower than that of defatted protein fl our and the emulsifying sta bility of the protein prepared by alkali solution and isoelectric pre cipitation was the lowest one A remarkable property of peanut protein products was its gel property which was determined in this study The resulting gel properties of IPPPC AAPPC and IAPPC were good compared with the results of rheological testing of common gel based foods The gel properties of IPPPC and IAPPC were the best which indicated that they were potential food ingredients But studies on the application of peanut protein concentrates to sausage products was limited and needed a further study In a word PPC could be a good source of protein fortifi cation for a vari ety of food products for protein defi cient consumers in developing countries as well as a functional ingredient for the peanut industry The production of PPC could also add value to defatted peanut fl our a low value by product of peanut oil production Acknowledgements This work is part of the research projects of the Science and Technology Department 11th Five year Plan State science and technology support projects serial number 2006BAD05A01 09 The authors gratefully acknowledge its fi nancial support The authors also wish to thank Prof Zhenzhen Yang for her advice dur ing composing this paper Ms Chunhong Li CAAS Beijing for allowing access to her TA 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