Three varieties of sweet corn (Zea mays L.) , including two supersweet (Crisp 'N Sweet 710 and Rogers 3376) and one normal sweet (Jubilee), were harvested at six stages of maturity (80-72% moisture for supersweet and 75-68% moisture for normal sweet) at three days intervals. Changes in physical and chemical properties over the 15 day harvest period and effects of steam blanching on carbohydrate composition of both genotypes of sweet corn were determined. Moisture content of the kernels decreased with maturity. A quick microwave oven moisture method for determining moisture content of normal sweet and supersweet corn was evaluated and found to be a good alternative method for the time-consuming standard AOAC vacuum oven method. Yield (as represented by average ear weight) increased linearly with maturity. Percent soluble solids was determined to be a satisfactory maturity index for normal sweet corn but not for supersweet corn. The pericarp content in the normal sweet corn Jubilee increased 25% over the 15-day harvest period compared to a mean of 5-6% in the supersweet varieties. Values of the shear press tests were not significantly correlated to % moisture, and only values of compression work showed a positive trend to increase with maturity. Total sugars of supersweet corn averaged 2-3 times higher and decreased more slowly than those of normal sweet corn in the comparable maturity range for processing. Sucrose was the major sugar in both corn genotypes and represented about 80% of the total sugars (9-20% dry weight) in normal sweet corn versus 90% of the total sugars (30-45%) in supersweet corn. Polysaccharides consisted mainly of starch in supersweet corn and of water soluble polysaccharide (WSP) in normal sweet corn. Normal sweet corn contained about twice as much polysaccharides as did supersweet corn. Percent total polysaccharides increased with maturity. Although higher in sugars, supersweet corn had lower % total carbohydrates than normal sweet corn due to its low polysaccharide content. Blanching of corn-on-the-cob for 10 minutes in 99°C steam resulted in a significant loss of sugars. Blanching did not significantly reduce total polysaccharides of sweet corn. / Graduation date: 1990