Most people expect corn kernels to be bright yellow, so observing white kernels can be surprising. Corn coloration is determined by pigments, primarily a class of compounds called carotenoids. The absence or reduction of these pigments is what makes corn appear white. This lack of color is not always a problem, but can be due to three factors: the corn’s natural variety, a health issue during growth, or a specific post-harvest processing technique.
The Role of Genetics and Pigmentation
The most straightforward reason for white corn is its genetic makeup, as the color is simply bred into the variety. Yellow corn obtains its vibrant hue from carotenoids, which are natural pigments synthesized within the kernel’s starchy endosperm. White corn varieties, such as Silver Queen, naturally lack the necessary dominant gene to produce these pigments. The white color results when the kernel carries the homozygous recessive version of the \(Y1\) gene, essentially turning off the metabolic pathway that synthesizes yellow pigments.
The resulting kernel is devoid of yellow coloration, exposing the naturally pale starch that makes up the bulk of the endosperm. This genetically determined lack of pigmentation is a desirable trait in many types of sweet corn, dent corn, and flour corn. The white appearance is completely normal and indicates a healthy, mature kernel of that particular strain.
Nutrient Deficiency and Plant Health
When corn genetically programmed to be yellow turns white, the cause often lies in a pathological condition during growth. This whiteness is a symptom of chlorosis, which is the failure to produce enough chlorophyll, or albinism in severe cases. This discoloration can affect the leaves, stalk, and ultimately the developing kernels.
A deficiency in the micronutrient Zinc is a common cause of striking white or pale coloration, particularly in new growth. Zinc is crucial for enzyme function and pigment synthesis, so its absence inhibits chlorophyll production. Severe zinc deficiency can cause the newest leaves emerging from the whorl to be almost entirely white, a condition sometimes termed “white bud.”
Magnesium deficiency can also lead to a pale appearance, first showing as streaking between the veins of the lower, older leaves. Since Magnesium is a core component of the chlorophyll molecule, an inadequate supply directly impairs the plant’s ability to create the green pigment. Similarly, a lack of Nitrogen causes a general paleness that typically starts at the tip of the oldest leaves and moves down the midrib in a characteristic V-shape.
Environmental stressors can further complicate the issue, as sustained cold temperatures or excessive moisture can temporarily prevent the plant from taking up available nutrients. This leads to symptoms that visually mimic a true nutrient deficiency. Observing the specific pattern of the whiteness on the plant is the first step in diagnosing the underlying nutrient or environmental factor.
White Appearance in Prepared Corn Products
A third reason for white corn is a change that occurs after harvest, specifically during traditional processing methods. The most significant post-harvest treatment that alters corn color is nixtamalization, a process used to prepare dried corn for making hominy, grits, and masa dough.
Nixtamalization involves soaking and cooking the dried corn kernels in an alkaline solution, traditionally limewater or water containing hardwood ash. This high-pH environment initiates a chemical change that loosens and removes the outer hull (pericarp) from the kernel. Even if the original corn was yellow, removing the hull and exposing the starchy interior contributes to a much whiter appearance.
Furthermore, the alkaline treatment chemically affects the remaining kernel structure, often resulting in a noticeable bleaching effect. This process transforms kernels of various colors into a softer, paler product called nixtamal, which has a uniform white or off-white color. Dried dent corn also loses much of its remaining color vibrancy during the drying and processing required for long-term storage and milling.