Processing of Sweet Corn [chapter]

Mariusz Szymanek
2012 Trends in Vital Food and Control Engineering  
Trends in Vital Food and Control Engineering 86 tissue and forms the outer layer of the kernel. The thickness of the layer determines the kernel skin level of tenderness. This feature is important in the estimation of kernel quality for processing. As compared to other varieties, sweet corn is characterized by lower thickness of the epicarp, on average 25-30 μm (Ito and Brewbaker, 1991) . The epicarp is composed of a single layer of pericarp, in the cavities of which single cells of the
more » ... ells of the mesocarp are located. It also includes one or two layers of cross-cells and one or more tube cells adherent to the pericarp. The germ, located obliquely at the base of the kernel, is large and constitutes about 15% of the volume or 11.5-14% of the weight of the kernel. Germ size, however, is cultivar-related and may constitute 5% of the mass of the whole kernel (Puangnak, 1998) . In turn, the parenchyma is the largest element of the kernel. It is in the parenchyma that the sugars, starch, and water-soluble polysaccharides are accumulated in. In the phase of consumption ripeness, the consistency of kernels is soft, delicate, creamy, and the taste is sweet and fragrant (Reyes and Varseveld, 1982) . The kernel seed coat has colours from pale yellow to orange, often also with a violet tint and shiny. In the genotype of sweet corn, apart from the genotype of sweet corn, except gene su (sugary) gene determining the sweet taste and tenderness of the kernel, also other genes have been discovered, responsible for enhancing the sweetness and the taste and utility qualities -the gene se (sugary enhancement) and the gene sh2 (shrunken 2). Genetic combinations of the genotypes su and sh2 helped in the creation of very sweet cultivars (Simonne et al., 1999) . In the phase of full ripeness, sweet corn has wrinkled kernels, almost completely filled with vitreous parenchyma, mostly white or yellow in colour. The reserve substance of the parenchyma is composed of amylodexstrins which are responsible for the sweet taste. The kernel has a bulbous shape, oval, wedge-shaped or angular, a smooth or wrinkled surface, and white, yellow, read or brownish colouring. It is enclosed in a cover formed from fused pericarp and seed coat, beneath which there is a layer of aleurone cells, the parenchyma, and the germ. From the moment of pollination till harvest the cob of sweet corn undergoes numerous physical and chemical transformations which largely affect the taste and the quality of kernels. The taste is especially strongly affected by the transformations of sugars (Wong, 1994). With respect to the content of sugars, three types of sweet corn cultivars are distinguished: normally sweet cultivars, type su (sugary), with sugar content of 4-6%, cultivars with increased sugar content, type se (sugary enhancement) -6-8%, and very sweet cultivars, type sh2 (shrunken 2) -8-12%
doi:10.5772/35867 fatcat:3i2lmq4l4ba5vm4gtw57btft54