P1: SFK/UKS BLBS102-c42 P2: SFK BLBS102-Simpson March 21, 2012 14:27 Trim: 276mm X 219mm Printer Name: Yet to Come 801 42 Food Allergens provide nutritional requirements of neonates Human milk and the milks of dairy animals, such as cows, goats, sheep and buffaloes, have been extensively studied Humans are the only known mammals that consume the milk of other mammals, particularly from cows In fact, cow’s milk and cow’s milkassociated food have been deeply rooted as an important part of the human diet, and the dairy industry plays a huge role in supporting nutrition of humans and continues to be a backbone of the agri-food sector in many countries In developed countries, bovine milk and milk-derived products contribute about 19% of total dietary protein intake and 73% of calcium intake (Tome et al 2004) However, for some people, consumption of cow’s milk and cow’s milk-derived food has to be avoided due to milk allergy Recent studies have indicated that prevalence and persistence of cow’s milk allergy (CMA) in industrialised countries may be increasing In North America, incidence of CMA is estimated at 2.5% in children and about 1% in the adult population with a 75% outgrowing rate at the age of 16 (Sicherer and Sampson 2010) Major Milk Allergens β-Lactoglobulin (BLG, not found in human milk) and caseins, α-s1-casein in particular, are regarded as the principal allergens in cow’s milk (Kaminogawa and Totsuka 2003) A recent study of 115 CMA Japanese children identified casein as a major milk allergen with 107 (97.3%) children reacting positively to caseinspecific IgE, whereas 51 patients (46.6%) were positive to BLGspecific IgE (Nakano et al 2010) However, studies on large populations show that a high proportion of CMA patients are sensitised to multiple milk proteins, including proteins present in very low quantities, such as bovine serum albumin (BSA), immunoglobulins and lactoferrin, suggesting that all milk proteins could be potentially allergenic Sensitisation to caseins, BLG, and α-lactalbumin (ALA) appear to be closely linked However, sensitivity to BSA seems to be completely independent Epitope mapping of major milk allergens has revealed multiple allergenic epitopic regions within each protein (Busse et al 2002, Cocco et al 2003) Caseins Milk Protein Milk protein is a very complex mixture of molecules Thanks to advanced analytical techniques, over 200 types of proteins have been identified in bovine milk (Ng-Kwai-Hang 2002) These proteins can be arranged into five groups: caseins, whey proteins, milk fat globule proteins, enzymes and minor miscellaneous proteins Caseins and whey proteins make up almost all of the total milk protein composition, whereas the other groups are found in trace amounts (Table 42.1) Caseins can be separated from the other proteins by acid precipitation at pH 4.6 to form a coagulum However, the ratio of casein and whey in the milk varies among different species In human milk, the ratio is 40:60, in equine the ratio is 50:50 and in major dairy animals (cows, goats, sheep and buffaloes) the ratio is 80:20 Casein (CN) forms the main fraction of milk proteins and is subdivided into a number of families, including α-S1-, α-S2-, β-, κ- and γ -caseins The α-S1-casein (α-S1-CN) is a single-chain phosphoprotein of 199 amino acid residues and represents about 40% of total casein α-S1-CN is characterised by a high content of proline residues without disulfide bonds and the presence of a small amount of secondary structure, such as α-helix or βsheets Several epitope regions of α-S1-CN recognised by human IgE antibodies have been identified These regions include amino acid (aa) 19–30, aa86–103 and aa141–150 (Spuergin et al 1996), aa181–199 (Nakajima-Adachi et al 1998) and nine regions from amino acid residues 17 through 194 (Chatchatee et al 2001) Reasons for the differences in the dominant Table 42.1 Characteristics of the Major Proteins in Human and Cow’s Milk Proteins Whole caseins α-s1-Casein α-s2-Casein β-Casein κ-Casein γ -Casein Whey proteins β-Lactoglobulin α-Lactalbumin Immunoglobulins Serum albumin Lactoferrin Other Human (mg/mL) Cow (mg/mL) Molecular Weight (kDa) of Cow’s Milk Proteins Number of Amino Acids in Cow’s Milk 0 2.2 0.4 11.6 9.6 3.6 1.6 23.6 25.2 24 19 11.6–20.5 199 207 209 169 2.2 0.8 0.4 1.4 1.3 1.2 0.6 0.4 0.3 0.6 5.3 4.8 65% protein on dry basis), soya protein isolate (>90% protein on dry basis), textured soya products and soya hydrolysates or hydrolysed vegetable protein, which are used in a wide variety of products Other novel applications include soya ice cream and soya yogurt Allergenicity of soya foods is linked to the presence of residual soya proteins in these foods, so unless the soya ingredient used is highly refined (e.g refined soya bean oil), it is likely to contain allergenic protein and must be labelled when used in foods Studies conducted on soya lecithin have generally reported little or no allergy risk to sensitised individuals (Awazuhara et al 1998); however, hydrolysed and fermented soya products tend to retain some of their allergenic properties (Hefle et al 2005, L’Hocine and Boye 805 2007) Appropriate caution therefore needs to be exercised in the consumption of processed soya foods Soya Allergen Cross-Reactivities Although not confirmed clinically, a high cross-reactivity has been reported for different legumes (soya bean, peanut, lentils and beans; Yunginger 1990, Eigenmann et al 1996, Kalogeromitros et al 1996) This may be explained by the high amino acid sequence homology, which frequently occurs in plant proteins belonging to the same family Clinical coreactivity rates in peanut-allergic patients for soya using placebocontrolled challenges range between 1% and 6.5% (Burks et al 1988) Additionally, coexisting clinical reactivity has been reported between soya bean and cow’s milk for some allergic patients ranging between 5% and 50% depending on the specific group of patients studied (Host and Halken 1990, Burks et al 1994) PEANUT AND TREE NUT ALLERGENS Peanuts and tree nuts contain some of the most potent food allergens Prevalence rates of 0.8–1.5% for peanut allergy in the UK and US population and about 0.6% for tree-nut allergy in the US population have been reported (Grundy et al 2002, Sicherer et al 2003) Nuts and tree nuts belong to different plant species; however, they are frequently discussed together as their presence, handling and use in the food chain as well as the allergic responses they induce are often similar Peanut (Arachis hypogea) is a legume belonging to the family Leguminosae It grows under the ground in peanut pods containing the peanut seed Tree nuts, on the other hand, are edible seeds that grow on trees Examples of tree nuts that are of most concern as allergens are hazelnut (Corylus avellana), almond (Prunus dulcis), pistachio (Pistachia vera), macadamia nuts (Macadamia integrifolia), cashew (Anacardium occidentale), walnut (Juglans regia), pine nut (Pinus pinea), pecans (Carya illinoinensis) and Brazil nut (Bertholetia excelssa) Prevalence and Threshold Prevalence rates of peanut and tree nut allergies vary for different populations but appear to be higher in Western societies such as in Europe and North America Reported rates vary from 0.2 to 1.7 for peanut and 0.1 to 1.4 for tree nuts (Sicherer et al 2003) Allergic responses following ingestion of peanut and tree nuts by allergic patients range from oral pruritus, nausea, vomiting, urticaria, angiodema, bronchospasm, bronchitis, hypotension, anaphylaxis and death in some instances The reaction often occurs within minutes to a few hours after food consumption, and the severity of the response may be exacerbated by preexisting asthma (Sampson 2002, Sicherer et al 2003) Threshold doses for clinical reactivity reported in the literature range from 100 µg to 10 mg for peanut and 20 µg to 7.5 mg for tree nuts (Hourihane et al 1997, FDA 2006) Cross-reactivities between peanut, soya bean as well as other tree nuts have been reported (de Leon et al 2003) ... 96 95 87 88 90 85 96 94 89 89 90 84 Source: Adapted from Wal 2004 P1: SFK/UKS BLBS102-c42 P2: SFK BLBS102-Simpson March 21, 2012 14:27 Trim: 276mm X 219mm Printer Name: Yet to Come 42 Food Allergens... 21, 2012 80 2 14:27 Trim: 276mm X 219mm Printer Name: Yet to Come Part 8: Food Safety and Food Allegens epitopic regions reported by different researchers may be due to racial (Kaminogawa and Totsuka... of the white and yolk, both of which contain allergenic proteins Whole egg contains 12 .8? ??13.4% protein, 10.5–11 .8% fat, 0.3–1% carbohydrate and 0 .8? ??1.0% ash on a wet basis (Breeding and Beyer 2000)