The Study Of Microwave Technology And Quality Evaluation Of Peanut Butter

Most industrial and local peanut butter productions are linked to use oven roasters for roasting pre-treatment.This roasting technology take 20-60 min at 130-170℃ to heat peanut for peanut butter production.However,long-time high-temperature roasting brings high energy consumption problems,and at present,a comprehensive study on the peanut short-time pre-treatment method to produce peanut butter is rarely involved.Microwave technology,as a new heat treatment technology,has the characteristics of uniform and fast heating speed.Therefore,this study uses microwave technology to pretreat peanuts,determine the appropriate microwave pre-treatment conditions,and evaluate the physical quality,volatile and bioactive compounds,safety risk factors,and storage stability of microwave pretreated peanut butter.Firstly,to determine the appropriate pre-treatment condition,the Silihong variety was pretreated at different power(400 W,800 W,and 1200 W)and time(4,4.5,5,and 5.5 min).The pretreated peanut butter at different powers and times were compared to commercial for color CIE values(L*a*b*).The degree of sensory acceptance was evaluated by 18 trained panelists(a 9-point hedonic scale).Microwave pre-treatment condition at 800 W for 5 min was affirmed as the best condition due to its produced butter statistical similarity(P>0.05)with the commercial sample.Secondly,the optimized condition(800 W at 5 min)was further validated by applying it to four peanut cultivars in China(Baisha-1016,Yuhua-9414,Silihong,and Yuanza-9102),and their produced butters were compared to the commercial and oven treated(150℃,at 30 min)peanut butter.The pretreated peanut butters from Silihong,Yuahua-9102,and Yuhua-9414 with initial moisture(5.5-7%)showed no significant difference in commercial one(P>0.05).The variation(P<0.05)was observed in the peanut butter from the lowest moisture peanut(Baisha-1016).There was no significant difference between the CIE values a*and b*(P>0.05).The L*values vary significantly(P<0.05)but remain within the recommended range of peanut butter color(Hunter L*51-52).Baisha-1016(lowest moisture content)had significant(P<0.05)dark color after microwave treatment.Furthermore,the comparison between microwave and oven revealed that all the microwave pretreated peanut butter had significantly higher sensory and desirable peanut butter color than the oven treated samples.The peanut butter from the Biasha-1016 cultivar showed a lower sensory score due to over-roasting.The result of bioactive compounds suggested that a significantly(P<0.05)higher total polyphenol(35.20±1.76μmol GAE/g)was observed in pretreated microwave samples(Yuahua-9102)compared to commercial peanut butter(28.47±0.75μmol GAE/g)but similar in all oven treated samples.The free tocopherol content of the Silihong butter was 1.8 times higher(P<0.05),with the other samples showing statistical similarity(P>0.05)with the commercial peanut butter.On the other hand,except for Baisha-1016,all pretreated peanut butter showed significantly higher tocopherol content than the oven-treated samples.Additionally,the commercial peanut butter’s total phospholipid content was similar(P>0.05)with butter from Baisha-1016 and Yuhua-9414 treated with the microwave but lower in the oven treated samples.The phytosterol content of microwave oven treated samples was similar but higher in the commercial sample.The peanut butter safety test indicated no benzo[a]pyrene content was found in all peanut butter,including the butter obtained from microwave treated peanuts.Finally,the storage stability was determined by storing the samples at accelerated temperature(370 C)and testing the induction period,moisture accumulation,and peroxide value for a month at 10-day intervals.The induction period of microwave treated samples(19.80±0.99-14.22±0.23 hrs.)was significantly longer(P<0.01)than the commercial(10.64±0.13 hrs.)and the oven peanut butter(16.65±0.22-12.93±1.41)at the initial stage.Although rapid reduction was observed over storage time,the commercial peanut butter(10.64±0.13-4.68+0.19 hours)experienced statistically(P<0.05)higher reduction,followed by oven treated samples(16.65±0.22-5.88±0.15 hrs.)than all the butter treated with microwave(19.80±0.99-7.84±0.07 hrs.).And there was no indication of rancidity in all samples.Except for oven-treated samples,all the microwave samples showed statistically lower moisture content and peroxide values(P>0.05)with the commercial peanut butter at the initial stage before storage.Though there were an increase in moisture content and peroxide values in all samples as storage time progresses,a significant(P<0.05)higher increase was observed in the long-time(30 min)oven treated samples than the short-time(5min)microwave and commercial samples.However,the increase in peroxide values of all samples was ≤5.5,which could be below the permeable value(<15meg O2/kg oil).In general,the quality of peanut butter obtained through microwave pre-treatment in a short period(5min)was superior to both commercial and the long-time oven(30min)treated peanut butter.The finding could provide support and reference to promote microwaves’use for the production of peanut butter.