Food Biochemistry and Food Processing (2 edition)

BLBS102-c42 BLBS102-Simpson March 21, 2012 14:27 Trim: 276mm X 219mm Printer Name: Yet to Come

806 Part 8: Food Safety and Food Allegens

Major Peanut and Tree Nut Allergens

The major allergens identified in peanut are Ara h 1 (glycopro-

tein, vicilin, MW 63.5 kDa), Ara h 2 (glycoprotein, conglutin,

MW 17.5 kDa), Ara h 3 (legumin, MW∼60 kDa), Ara h 4

(legumin, MW 37 kDa), Ara h 5 (profilin, MW 14–15 kDa), Ara

h 6 (conglutin, MW 14.5 kDa), Ara h 7 (conglutin, MW 15.8

kDa) and Ara h 8 (pathogenesis-related protein, MW 16.9 kDa;

Wen et al. 2007, Rajamohamed and Boye 2010). Ara h 1 and Ara

h 2 are classified as major allergens and are recognised by the

sera of>90% of peanut-allergic patients. Ara h 3, Ara h 4, Ara h

5, Ara h 6, Ara h 7 and Ara h 8 are less frequently recognised by

the sera of peanut allergic individuals and are classified as minor

allergens (Wen et al. 2007, Rajamohamed and Boye 2010).

Allergenic proteins in tree nuts vary depending on the type of

nuts. In a voluntary survey report on tree nut allergy conducted

by Sicherer et al. (2001), 46% of tree-nut-allergic individuals

reacted to multiple tree nuts, and 54% reacted to single tree

nuts with the highest reactions being reported toward walnut

(34%), cashew (20%) and almond (15%) and lower allergic

responses to pecan (9%), pistachio (7%), hazelnut, Brazil nut,

macadamia nut, pine nut and hickory (less than 5% each). Table

42.3 provides a list of some of the major proteins identified in

tree nuts and their properties (Rajamohamed and Boye 2010).

Processing-Induced Changes in Peanut and

Tree Nut Allergenic Proteins

Processing induces changes in peanut and tree nut proteins,

which can modify their allergenic properties. Many research

studies have found, for example, that roasting increases the im-

munogenic properties of peanut compared to frying and boiling.

Using sera of peanut-allergic patients, Beyer et al. (2001) found

lower IgE-binding intensities of Ara h 1, Ara h 2 and Ara h 3 in

fried and boiled peanuts compared to roasted peanuts. Similarly,

Maleki et al. (2000) found significant increases in the allergenic

properties of roasted peanut compared to raw peanut. On the

contrary, Koppelman et al. (1999) reported no change in the

allergenicity of Ara h 1on heat treatment. Hansen et al. (2003)

also reported that dry roasting of hazelnut reduced its aller-

genicity compared to raw hazel nut. Differences in the effect of

the thermal treatment on the molecular structure of the proteins

and their solubility may explain the variations in the responses

reported.

FISH AND SHELLFISH ALLERGENS

Fish and shellfish represent one of the most common sources of

food allergens in the adult population. Fish and shellfish species

known to cause allergic reactions include but are not limited to

cod, flounder, grouper, haddock, halibut, hake, herring, mack-

erel, pike, sole, snapper, trout, crabs, lobsters, prawns, shrimps,

crayfish, octopus, squid, clams, mussels, oysters, scallops and

snails.

The major allergen in fish is parvalbumin (Gad c 1), a 12

kDa protein (O’Neil et al. 1993). Tropomyosin, with a MW

of∼36 kDa, is the major allergen found in shrimp, lobster,

crab and molluscs such as squid, oyster, snail, mussels, clam

and scallops (Daul et al. 1993a, 1993b). Both parvalbumin

Table 42.3.Major Tree-Nut Allergens and Their Characteristics

Tree Nuts Allergen

Molecular

Weight (kDa) Protein Family

Allergen

Type

Identified

Epitopes

Allergen

Stability References

Cashew Ana o 1 50 Vicilin (7S) Major 11 Thermostable 51, 54

Ana o 2 33 and 53 Legumin (11S) Major 22 Thermostable 53, 54

Ana o 3 12 Albumin (2S) Major 16 Thermostable 52, 54

Walnut Jug r 1 14 Albumin (2S) Major 3 NR 55, 56

Jug r 2 44–47 Vicilin (7S) Major NR NR 57

Jug r 3 9 LTP NR NR NR 58

Jug r 4 NR Legumin (11S) NR NR NR 58, 76

Hazelnut Cor a 1 18 PR-10 Major NR Thermolabile 59, 61

Cor a 2 14 Profilin Major NR NR 59

Cor a 8 9 LTP Major NR NR 63

Cor a 9 35–40 Legumin (11S) Major NR NR 63

Cor a 11 47 Vicilin (7S) NR NR NR 63

Brazil nut Ber e 1 9 Albumin (2S) Major NR Thermostable

and resistant

to proteolysis

64, 65

Ber e 2 22 and 35 Legumin (11S) Minor NR NR 67

Almond NR 45 Vicilin (7S) Major NR NR 70

NR 20–22 and

38–42

Legumin (11S) Major NR NR 68, 69

NR 12 Albumin (2S) Major NR NR 70

Source: Adapted from Rajamohamed and Boye 2010.

MW, molecular weight; NR, - not reported; PR, pathogenesis-related protein family; LTP, lipid transfer protein.