Submitted to: Carbohydrate Polymers
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/8/2006
Publication Date: 2/1/2007
Citation: Peterson, S.C., Eller, F.J., Fanta, G.F., Felker, F.C., Shogren, R.L. 2007. Effects of critical fluid lipid extraction on the gelatinization and retrogradation of normal dent cornstarch. Carbohydrate Polymers. 67(3):390-397. Interpretive Summary: The ability of cornstarch to thicken food products is one of its key traits that make it an important commodity. One of the factors that influence the thickening properties of cornstarch is the amount of fat present in the starch to begin with. Although the fat content of cornstarch is very low (less than 1% by weight), the fat present in starch has a very large impact on its thickening properties. In this paper a new method of extracting some of the fat from starch, called critical fluid extraction, was investigated and compared to a well known method for extracting all of the fat. These two methods were then compared to regular starch that had not been defatted at all. Critical fluid extraction is a rapid and non-toxic method to use so positive results could ultimately translate to less processing time for modified starches. Previous research regarding the fat content of starch and its effects on how starch forms a gel has shown much conflicting data. In this paper we looked at not only how much fat was extracted but also the starch concentration. This may help explain some of the previous conflicting data. We saw results that suggest swollen starch granules that have had fat extracted from them may become more rigid than normal starch granules. At low starch concentration these swollen starch granules do not interact and may result in a lower consistency, but if the starch concentration is increased enough so that these more rigid granules interact with each other, an increase in viscosity (how thick the gel is) is seen. This research will benefit starch scientists because it clears up some of the past contradictions regarding fat extraction and its effects on how starch thickens. Also, the critical fluid extraction method is useful because it allows scientists to create starch samples that are only partially defatted, which can help provide scientific insight to other starch research.
Technical Abstract: Critical fluid extraction of native lipids from cornstarch using 80/20 (v/v) CO2/ethanol and 100% ethanol was carried out in order to see what effects each solvent would have on the starch pasting profile. The results were compared with cornstarch defatted by refluxing with 75/25 (v/v) n-propanol/water. Pure ethanol extracted more native lipid than CO2/ethanol, and extraction improved when the initial moisture content of the starch was increased from 10% to 19%. Granules became less swollen and less deformable with increased lipid extraction. Paste viscosity studies carried out at starch concentrations less than 8% yielded lower peak and setback viscosities of lipid-extracted cornstarch relative to native cornstarch. However, above 8% starch concentration, swollen granules were in more intimate contact, and the added rigidity caused by lipid extraction yielded much higher peak viscosities relative to the starch control. Lipid-extracted cornstarch samples at concentrations above 8% showed plateau rather than peak viscosities reflecting the limited swelling power of the granules, and the defatted samples displayed less viscosity breakdown due to their increased granule rigidity.