15D-25 |
Process simplification and modification affecting physico-chemical properties of chitosan and conversion efficiency of chitin |
S. K. ROUT and W. Prinyawiwatkul. Department of Food Science, Louisiana State University Agricultural Center, Baton Rouge, LA 70803-4200 Traditional isolation of chitin from crawfish shells involves three sequential steps: demineralization, (DM, removing calcium carbonate/phosphate), deproteinization (DP), and decolorization (DC, removing mainly astaxanthin). The first two steps can be reversed (i.e., DMDP or DPDM). Chitin is converted to chitosan by deacetylation (DA). Isolation steps may be shortened, depending on intended applications of chitosan. For example, DC may be unnecessary if chitosan is used as film coating on citrus fruits. During DA, some proteins are removed, thus DP may not be necessary. This study investigated effects of (1) reversing sequence (DPDM) and (2) eliminating DP and DC steps on physico-chemical properties of chitosan and conversion efficiency of chitin. Six processes: DM, DP, DMDP (non-decolorized chitin), DPDMDC (decolorized chitin), DPDMDCDA (chitosan), and DMDA (non-deproteinized/non-decolorized chitosan) were investigated. Nitrogen content, CIE-L*a*b* color, bulk density (g/ml), and conversion efficiency (%CEF) were determined. DA of DPDMDC did not affect bulk density. Without DP and DC, bulk density of chitosan significantly increased. Color of DPDMDCDA-chitosan was creamy-white, having greater hue angle, greater L* and lower a* values than that of DMDA-chitosan (light pink). Nitrogen content of DMDA-chitosan was 6.96% compared to 7.4-7.9% of commercial crab chitosans. DA removed 19% protein from demineralized shells. Deproteinized and demineralized shell once dried was not an effective substrate for decolorization. Simultaneous DM and DC should be done immediately after DP of shells. CEF of demineralized shell to non-deproteinized/non-decolorized chitosan (DMDA) was 52.5%. CEF of chitin (DPDMDC) to chitosan (DPDMDCDA) was 75%. About 14% yield of chitosan (DPDMDCDA) from crawfish shell was achieved. This study shows that isolation steps for chitosan production can be reduced, which, in turn, would lower production cost and produce less chemical wastes compared to the traditional process. Removal of DP and DC steps affects some properties of chitosan that hold the key to its applications.
Session 15D, Food Engineering: Processing Technologies
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