See also Maize/Corn Pollen.

Common Names: Maize, Corn, Sweet Corn, Indian Corn, Field Corn

Cultivars may be divided into six general types: Popcorn (everta), Flint Corn (indurata), Dent Corn (indenta), Flour Corn (amylacea), Sweet Corn (saccharata) and Pod Corn (tunicata).

There are, however, only two more basic types: 'Sweet Corn' is distinguished from 'Field Corn' by the high sugar content of the kernels at the early 'dough' stage and by wrinkled, translucent kernels when dry.

The original habitat was probably South America or Mexico where is was the staple diet of the American Indian. Maize is now grown almost anywhere summers are reasonably warm although approximately 50% of the world's maize is produced in the USA. It is one of the most commonly grown foods. It is a staple cereal of the human diet in Central and South America and in many parts of Africa. It is extremely important in livestock rearing, food processing and other commercial activities in developed countries.

The plant is a single-stemmed annual, sometimes over 3m long. It terminates in the tassle or staminate flowers and bears female flowers and grains on 'ears' arising at the leaf axils. The smooth leaves, usually green and usually drooping can be over a metre long. In the Northern Hemisphere, it is in flower between July and October, and the seeds ripen between September and October.

Maize is cultivated and not known in the wild.

Few plants are grown more extensively or put to more diversified uses than Maize. It is a staple cereal for humans in Central and South America, and in many parts of Africa. In the US and Europe it is used almost entirely for animal feeding, as grain or fodder. But it is important as a vegetable, and as the snack Popcorn. Kernels may be eaten straight from the cooked cob or cut off and used in succotash, custards, fritters, soups and chowders. Kernels are also used in mixed pickles and vegetable relishes. Corn meal, grits, and hominy are prepared forms of Maize kernels. Maize is also converted into various substances that have a wide range of usage, such as starch, syrup, dextrin, oil, and zein. Maize serves in the making of whiskey and other alcoholic products, and condensed milk. The roasted seed is a coffee substitute. Riboflavin and nicotinamide are added to fortified maize, and in some countries, e.g., South Africa, other substances as well.

The various parts of the plant have been used in the treatment of a variety of ailments, including diabetes, gonorrhoea, gout, nose bleeds, ulcers, menstrual pathologies, rheumatism, cancer, tumours, warts, corns, wounds, Bright's disease, dropsy, dysentery, gingivitis, hepatitis, hypertension, inflammation, influenza, metritis, oliguria, pneumonia, prostatitis, renitis, and urogenital ailments.

Allergens/Function:

Allergens:
Zea m 14, a 9 kDa Lipid Transfer Protein (isolated from corn flour). (Pastorello 2000 ref.4265 1) (Midoro-Horiuti 2001 ref.5021 0) (Pantoja-Uceda 2001 ref.7280 3) (Diaz-Perales 2002 ref.6865 4) (Asero 2002 ref.6858 2) (Heiss 1996 ref.2428 1) (Scheurer 2001 ref.4187 3)

A chitinase has been isolated from Zea mays seeds. (Verburg 1992 ref.7279 5) (The allergenicity of this chitinase was not evaluated. Ed.)

A 22 kDa protein from maize seeds with a 52% homology with the sweet protein thaumatin and 99% homology with the 22 kDa trypsin/alpha-amylase inhibitor has been isolated. (Huynh 1992 ref. 7281 4). (The allergenicity of this protein has not been evaluated. Ed.)

Sera from 19 (86%) of the 22 patients with systemic symptoms after maize ingestion and positive skin prick test responses and serum-specific IgE antibodies to maize recognized a 9-kd protein, thus confirming this as the maize major allergen. (Pastorello 2000 ref.4265 1) A 16 kDa allergen, recognized by 36% of patients, was also isolated and shown to be the maize inhibitor of trypsin. This protein cross-reacts completely with grass, wheat, barley, and rice trypsin inhibitors. (Pastorello 2000 ref.4265 1)

A 50 kDa allergen, belonging to the Reduced Soluble Protein fraction (RSP), has been isolated and shown to be stable to heat and digestion. In a study of 16 patients with specific IgE to maize, only 6 patients were symptomatic. These 6 patients were DBPCFC-positive on challenges, and skin specific IgE with the purified RSP fraction was positive for all of the 6 DBPCFC-positive patients. (Pasini 2002 ref.5660 1)

In an individual with corn dust-induced occupational asthma and rhinitis, 10 IgE-binding components (9 to 140 kD) were detected within the corn dust extracts. (Park 1997 ref.2384 3)

Anaphylaxis in 2 nurses to cornstarch glove powder is described. Both exhibited positive prick skin tests to cornstarch powder in water, with resultant anaphylaxis in one and negative prick skin tests and RAST to corn. Analysis of the powder revealed only glucose and inorganic salts. The authors state that they suspect that cornstarch is the responsible allergen. (Seggev 1990 ref.7598 1)

Normal corn contains about 7-13% protein that can be fractionated into various solubility classes. The salt-extractable fraction (albumins and globulins) mainly comprise proteins with metabolic functions. Extraction with aqueous alcohol isolates the prolamin fraction that contains the storage proteins of the seed. These constitute around 60-70% of the corn endosperm proteins and are called zeins. Thse are various polypeptides and classified as alpha, beta, delta and gamma zeins. The Reduced Soluble Proteins are alcohol extractable and soluble in water. Also present is an alcohol-insoluble glutelin fraction. (Pasini 2002 ref.5660 3)

In a previous study a 9-kd lipid-transfer protein (LTP) was identified as the major allergen of raw maize in a population of 22 anaphylactic patients. However, the stability of this protein in cooked maize is unknown.

This study investigated the allergenicity of 5 maize hybrids and its modification after different thermal treatments by using sera from anaphylactic patients and patients with positive double-blind, placebo-controlled food challenges. All raw maize hybrids showed similar protein and IgE-binding profiles. The SDS-PAGE of all the heat-treated hybrids demonstrated a decreased number of stained bands in respect to the raw samples. The IgE immunoblotting demonstrated that the major allergen of the water-soluble, total zein, total protein, and glutelin fractions was a 9-kd protein identified as an LTP and a sub-tilisin-chymotrypsin inhibitor (in total zein fraction). The IgE-binding capacity of this 9-kd protein remained unchanged after thermal treatments, even though circular dichroism demonstrated an altered secondary structure. A 160 minutes of thermal treatment at 100oC almost totally eliminated the IgE-binding activity of the higher MW bands but did not affect that of LTP. (Pastorello 2003 ref.8563 5)

USES:
May also be used to produce corn starch, which is found in sauces, dressings, gravies, and other foods requiring thickening.

Adverse Reactions:

IGE AND IMMUNE:
Allergic reactions. Angioedema. Abdominal pain, nausea and vomiting. Rhinitis. Bronchospasm. Cutaneous complaint. Gastrointestinal symptoms. Respiratory complaints. Atopic dermatitis.

Anaphylaxis. (David 1984 ref.485 12) (Pastorello 2000 ref.4265 4) Double-blind, placebo-controlled corn challenge resulting in anaphylaxis. (Tanaka 2001 ref.4185 2)

Allergic reactions due to corn-starch powder used as glove-lubricant-powder. Symptoms included urticaria, intermittent dyspnea, oculorhinitis, angioedema, and asthma (Crippa 1997 ref.2383 4)

Allergic reactions (e.g., urticaria) seen with corn syrup, corn dextrimaltose, corn invert sugar, corn isomerized dextrose and corn D-psicose (Howard 1959 ref.527 87) (Nishioka 1983 ref.528 01) (Nishioka 1984 ref.529 02)

If corn oil is not purified it may contain maize/corn protein.

Food-dependant exercise-induced anaphylaxis to corn. (Pauls 1998 ref.2381 5) A study reports on 7 cases of food-dependant exercise induced-anaphylaxis. The responsible foods were wheat (2 cases), corn, barley, shrimp, apple, paprika and mustard. (Mathelier-Fusade 2002 ref. 7125 2)

Patients allergic to maize may also be allergic to maize pollen, as Zm13 and homologous proteins are conserved plant allergens (Heiss 1996 ref.2428 3)

I.V administration of a corn-derived dextrose solution, a 23-y-old pregnant female patient admitted to the hospital at term gestation developed an anaphylactic reaction. Orofacial swelling, difficulty in breathing, hypotension, cardiac arrhythmia, voice hoarseness, total body warmth and flushing occurred within 8 min of initiation of a 5% dextrose Lactated Ringer's solution. A sample of suspect solution found no contamination. Although the reaction elicited in this patient was rare, clinicians should be aware of the possibility of corn allergy due to the administration of i.v. fluids containing corn-derived dextrose. (Guharoy 1991 ref.5633 2)

The 10 chief offenders among food allergens are cow's milk, chocolate and cola (the kola nut family), corn, eggs, the pea family (chiefly peanut, which is not a nut), citrus fruits, tomato, wheat and other small grains, cinnamon and artificial food colors. (Speer 1976 ref.1025 4)

In 34 children with atopic dermatitis, 33 were SPT positive with wheat and 18 with oats. Positive RAST to wheat and oats could be detected in 32 and 30 samples respectively. SPT with rice, corn, millet or buckwheat was positive in 16/34 patients. (Varjonen 1995 ref.7564 1)

Sixteen subjects with SPT and CAP-FEIA positivities to corn flour were examined. Only six of them complained of suffering from urticaria and/or other symptoms after ingestion of corn-based foods. Only 6 patients challenged with cooked corn flour (polenta) developed symptoms following oral challenge. SPT and CAP-FEIA positivities to corn flour had no clinical significance for most of the patients and food allergy to corn has to be proved by DBPCFC. A 50 kDa protein was isolated and was shown to be stable to cooking and digestion. (Pasini 2002 ref.5660 8)

A significant association exists between recurrent serous otitis media and food allergy was demonstrated in 81 of 104 patients. An elimination diet resulted in a significant amelioration of the disease in 86% of the patients and a challenge diet provoked recurrence of symptoms in 94%. The highest frequency was seen with milk, wheat, egg, peanut, soy and corn, and <10% were seen with orange, tomato, chicken and apple. (Nsouli 1994 ref.7725 6)

OCCUPATIONAL EXPOSURE:
Baker & bakery, mill worker, animal feed industry

The most frequent positive skin prick reactions to occupational allergens in a group of 35 men working in an animal food processing plant were to fish flour (82.9%), followed by carotene (77.1%), corn (65.7%), four-leaf clover (62.9%), sunflower (54.3%), chicken meat (31.4%), soy (28.6%), and yeast (22.7%) (Zuskin 1992 ref.2807 1)

Occupational asthma to corn flour in bakers and millers (Quirce 1998 ref.2386 8) IgE mediated occupational asthma and rhinitis to grain dust. (Park 1997 ref.2384 3) Specific IgE, IgG and IgG4 antibodies to corn dust in exposed workers (Park 1998 ref.2379 3)

In 42 employees working in the animal feed industry, 15/42 (34.9%) subjects had work-related respiratory dysfunction associated with or without nasal symptoms. (Park 1998 ref.2380 1) In 32 swine farmers, 37% were reported to be allergic to corn flour. (Zuskin 1991 ref.7597 1)

Contact urticaria and anaphylactoid reaction from cornstarch surgical glove powder. (Assalve 1988 ref.7599 1) Anaphylaxis in 2 nurses to cornstarch glove powder is described. Both exhibited positive prick skin tests to cornstarch powder in water, with resultant anaphylaxis in one and negative prick skin tests and RAST to corn. Analysis of the powder revealed only glucose and inorganic salts. The authors state that they suspect that cornstarch is the responsible allergen. (Seggev 1990 ref.7598 1)

NON IMMUNE:
In 60 migraine patients, the commonest foods causing reactions were wheat (78%), orange (65%), eggs (45%), tea and coffee (40% each), chocolate and milk (37%) each), beef (35%), and corn, cane sugar, and yeast (33% each). (Grant 1979 ref.1242 1)