Supercritical Carbon Dioxide Treatment to Inactivate Aerobic Microorganisms On Alfalfa Seeds

Supercritical Carbon Dioxide Treatment toInactivate Aerobic Microorganisms on Alfalfa Seeds
December2001
Journal of Food Safety, Volume 21, Number 4
Angela M. Mazzoni, Ratna R. Sharma, Ali Demirci, Department of Agricultural andBiological Engineering;

GregoryR. Ziegler, Department of Food Science

PennsylvaniaState University

ABSTRACT-The supercritical carbon dioxide (SC-CO2) process involves pressurizing CO2 in achamber, which generates liquid phase of carbon dioxide.  Pressurizedliquid CO2 has a strong extraction capability of organic and inorganiccompounds. 

Therecent studies have also demonstrated that antimicrobial effect of SC-CO2 dueextraction some cellular components of microorganisms.  The efficacy of asupercritical carbon dioxide treatment on alfalfa seeds contaminated withEscherichia coli K12 was tested at 2000, 3000, and 4000 psi at 50C. Samples were treated for 15, 30, and 60 min at each pressure.   Afterpummeling the seed samples in 0.1% peptone water, the initial and finalEscherichia coli and total aerobic bacteria on the seeds were determined byplating on 3M Petri Films.  After 48 h of incubation at 37C, the colonieswere enumerated.

Treatedseeds were evaluated in terms of germination characteristics.  For aerobicplate count, the effect of pressure in the range of 2000-4000 psi was notstatistically significant (p>0.05) even though 85.6% inactivation wasachieved at 4000 psi for 60 min.

For E.coli, the reductions for 2000, 3000, and 4000 psi treatments for 15 min were26.6, 68.1, and 81.3%, respectively.  As the time was increased from 15 to60 min at 4000 psi, the percent E. coli reduction increased from 81.3% to 92.8%.

Thepercent germination for all treatments was over 90%. There was no significantdifference (p > 0.05) in the germination rate of treated and untreated seeds. Supercritical carbon dioxide treatments demonstrated a reductionof E. coli K12 and total aerobic counts without affecting the germinationharacteristics of alfalfa seeds (p<0.05).  This study was a step in thedirection of improving safety of alfalfa seeds used to produce fresh sprouts,which have been the cause of several outbreaks.