Hermetic and modified atmosphere storage of shelled peanuts to preventfree fatty acid and aflatoxin formation


Abstract: The development of free fatty acids (FFA), molds and aflatoxins formation wasstudied on peanuts with 7.0% and 8.0% moisture contents stored under hermetically sealedconditions or in an atmosphere of 99% carbon dioxide and in comparison to aerated storage at30 ± 1°C for 3 months. The laboratory trials were carried out using 0.95l capacity mason jarscontaining clean peanuts or peanuts with 3% broken peanuts at the two moisture content levels.In addition, semi commercial trials were carried out using 20kg of sound peanuts stored inhermetic SGBIIZ (GrainPro Inc.) bags at the same two moisture contents and the controlscontaining 7kg of sound peanuts were stored in ordinary PE bags. Each trial was replicated 3times. Moisture content, FFA (% of oleic acid), Colony Forming Units (CFU) of molds and B1,B2 G1 and G2 aflatoxins were checked on the outset of storage and after 3 months. Respirationrates based on the oxygen consumption of the microflora and the peanuts and the carbon dioxideevolved were monitored periodically. The fastest respiration rate (oxygen depletion) obtained inthe jars was with 8% moisture content peanuts containing 3% broken nuts after 18 days while at7% moisture content sound peanuts reduced its oxygen concentration to a level of 1% after 84days. In the SGBIIZ hermetic bags, at the 8% moisture content, the oxygen was depleted after 44days compared to the laboratory tests in jars which the lowest oxygen was obtained after 28 days.In all trials, aflatoxins level was below the threshold limit (≤ 0.3μg/kg). In peanuts stored underhermetic conditions the CFU formation (≥ 1.3*104) and FFA rise (≥ 0.57) were suppressedcompared to the aerated samples. Best quality preservation for peanut storage with low CFU(≤ 9.7*101) and low FFA (≤ 0.77) was obtained under controlled atmosphere of 99% carbondioxide for both moisture contents in peanuts containing 3% broken.

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