Effect of Heat on the Anaphylactic-Sensitising Capacity of Cows' Milk, Goats' Milk, and Various Infant Formulae Fed to Guinea-Pigs
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Arch Dis Child: first published as 10.1136/adc.56.3.165 on 1 March 1981. Downloaded from Archives of Disease in Childhood, 1981, 56, 165-171 Effect of heat on the anaphylactic-sensitising capacity of cows' milk, goats' milk, and various infant formulae fed to guinea-pigs P MCLAUGHLAN, K J ANDERSON, ELSIE M WIDDOWSON, AND R R A COOMBS Division of Immunology, Department of Pathology, and Department of Medicine, University of Cambridge, Addenbrooke's Hospital, Hills Road, Cambridge SUMMARY Cows' milk-fresh, boiled, and processed in different ways for the domestic market, and various infant milk formulae-was investigated for its sensitising capacity in the guinea-pig after being fed for 37 days. The anaphylactic sensitising capacity was considerably reduced by heat-treatment. As heat becomes more intense and more prolonged so P-lactoglobulin and casein become less sensitising. It should be stressed that these were results from experiments on guinea-pigs drinking milk. Should they be found to apply to the human infant too, it seems that it would not be impossible to manufacture a non-sensitising but fully nutritive milk product. The sensitising capacity of fresh and boiled goats' milk was examined too, and it was found that boiling reduced the sensitising capacity to an even greater extent than was the case with cows' milk. copyright. In recent years there has been a resurgence of interest heat-treated milk, or spray-dried whole cows' in breast feeding. Human milk is once again popu- milk (reconstituted with water), severe anaphylactic larly recognised as being a nutritionally adequate reactions could be provoked by injecting the diet for the human infant. The protective properties guinea-pigs with PLG either intravenously3 or of human milk in terms of local protection against intratracheally.2 4In contrast, anaphylactic reactions http://adc.bmj.com/ gastrointestinal and systemic infection are recognised. to ,BLG could not be similarly provoked in guinea- However, in Western countries, babies are still pigs that had been drinking 'evaporated milks'. mainly bottle fed. Although most infants thrive on Since these three types of milk consisted simply of bottle feeding with preparations based on cows' whole cows' milk it seemed that the physical treat- milk without any apparent ill effects, a few develop ment to which the milks had been subjected was some form of sensitisation to cows' milk and become responsible for this variation in sensitising capacity. unable to tolerate it because of gastrointestinal, Accordingly it was decided to investigate in greater on September 29, 2021 by guest. Protected dermatological, or respiratory problems. detail the effect of heating milk for different times As part of a larger study on the relevance of cows' and to varying degrees on its anaphylactic proper- milk sensitivity to the sudden infant death syndrome, ties in the guinea-pig, and to include milk from the a guinea-pig model for studying anaphylactic goat as well as the cow. sensitivity to cows' milk has been developed.' It has Infants today are rarely fed on whole cows' milk, been shown that guinea-pigs, after drinking milk but on a variety of proprietary formulae based on ad libitum for 37 days, develop anaphylactic cows' milk heated and treated in different ways. sensitisation.2 These formulae are designed to resemble human Recently, using this guinea-pig model, the milk to a greater or lesser extent, especially with sensitising capacity of various infant formulae and regard to the concentration of protein and inorganic cows' milk preparations was compared.3 It was constituents, particularly sodium and phosphorus, found that infant formulae varied considerably in but little attention has been given to lowering the their sensitising capacity per os, particularly in sensitising capacity of bovine milk proteins. The regard to sensitisation to P-lactoglobulin (fLG). It present study was designed to test such infant foods, was found that after 37 days of drinking either ultra compare the results with whole cows' milk treated 165 Arch Dis Child: first published as 10.1136/adc.56.3.165 on 1 March 1981. Downloaded from 166 McLaughlan, Anderson, Widdowson, and Coombs in various ways, and as far as possible, to relate the Controls. Each experiment included a group of results obtained with the proprietary foods to the guinea-pigs drinking water and a group drinking treatment they receive during manufacture. SMA pasteurised milk. These two groups were challenged formulae were selected for special study since the by injection with pasteurised milk on day 37. All the same ingredients are subjected to a different heat animals that drank water remained unaffected, but treatment in the manufacture of each preparation. all the animals that drank milk died of anaphylaxis. Materials and methods Milk and isolated milk proteins for intravenous challenge. Before injection the milks were centrifuged Guinea-pigs. Female Dunkin-Hartley guinea-pigs at 10 000 x g for 5 min in a Hawksley microfuge to aged 2-4 weeks on arrival from a commercial clear the inoculum of fat and insoluble material. breeder (Bantin and Kingman) were used. At the Isolated milk proteins-namely t3LG and casein- start of each experiment the guinea-pigs were aged were obtained from the National Institute for 4-6 weeks. Research in Dairying, Shinfield. The intravenous challenge consisted of 0 5 ml of Diets. RGP guinea-pig pelleted diet (Rank, Hovis, either microfuged milk at the concentration fed or McDougall) was fed to the animals. This pelleted isolated milk protein at a concentration of 6 mg/ml. diet had been shown to be free of cows' milk by immunological testing. The guinea-pigs received Passive cutaneous anaphylaxis reactions. The guinea- water or milk to drink ad libitum as indicated. pigs were bled by cardiac puncture on day 35 for passive cutaneous anaphylaxis (PCA) testing.4 The Milks tested. Table 1 gives a description of the sera were diluted 1:2 for intradermal injection and milks studied. There were 6 kinds of liquid whole thus could underestimate low serum levels of skin cows' milk differing only in the heat treatment each sensitising antibodies. had received, one liquid skimmed milk, one spray- dried whole cows' milk, and one spray-dried Results skimmed cows' milk. There were also 4 varieties of Experiment 1. copyright. the proprietary infant formula known as SMA, and goats' milk-both unheated and boiled. Anaphylactic sensitivity of guinea-pigs (drinking All infant formulae were prepared as recommended various cows' milk preparations) to the milk fed, and for infant feeding at about comparable protein also to 3LG and casein concentrations (20mg/ml protein, Lowry estimation). In previous studies guinea-pigs, after drinking milk Table 1 Composition and treatment ofmilks http://adc.bmj.com/ Designation Composition Treatment Cows' milk Raw Whole milk Unheated and untreated Pasteurised Whole milk Heated at 720C for 20 seconds Ultra heat-treated Whole milk Heated at 1400C for 1-2 seconds Boiled Whole milk Heated to 1000C and allowed to cool Evaporated Whole milk Heated to 950C for 10 min, evaporated under reduced pressure at 500C, autoclaved in cans at 110-1 150C for 15-20 min Sterilised Whole milk Autoclaved at 112.8-114-40C for 20 min on September 29, 2021 by guest. Protected Spray-dried Whole milk Uncertain, but see SMA powder. Cows' milk, skimmed Sterilised Skimmed milk Autoclaved at 1 10°C for 20 min Spray-dried Skimmed milk Uncertain, but see SMA powder SMA powder Skimmed cows' milk, lactose, vegetable Spray-dried* and animal fats Gold Cap powder Spray-dried* Whey, skimmed milk, lactose, vegetable Whey concentrated in falling film evaporator Ready to feed liquid *.* and animal fats at 720C for 15 seconds. Electrodialysed Diluted and at 370C, other ingredients added sterilisedt Liquid concentrate I ** *Sterilisedt Goats' milk Raw Whole milk Unheated and untreated Boiled Whole milk Heated to 1000C and allowed to cool * 1050C for 30 seconds, then cooled to 160C. Heated in preheater to 780C then into spray-drier and raised to 1670C, drying occurs instantaneously. tDiluted and heated to 770C for 16 seconds, sterilised at 1210C for 4.6 min. tHeated to 770C for 16 seconds, sterilised at 1220C for 5.6 min. Arch Dis Child: first published as 10.1136/adc.56.3.165 on 1 March 1981. Downloaded from Effect ofheat on the anaphylactic-sensitising capacity ofcows' milk 167 for 37 days, were tested for sensitisation by challenge on cows' milk, several preparations of whole milk with isolated milk proteins-namely tLG and were tested. In these milks the proportions of the casein. It was considered that whole milk (as fed) constituents had not been altered (unlike infant would provide a more critical challenge. In this formulae), they differed therefore only in the heat experiment the animals were challenged with whole treatment they had received. milk (as fed), and with 3LG and casein. Groups of 10 guinea-pigs were given variously Groups of guinea-pigs were given various treated whole cows' milk (Table 3) to drink for 37 formulae to drink for 37 days (Table 2). Each days. On day 35 each was bled and the serum was guinea-pig was bled on day 35 and the serum was used to study the PCA reaction. On day 37 the used to study the PCA reaction. On day 37 each guinea-pig was challenged by intravenous injection was challenged by intravenous injection of either the of the milk fed (Table 3). Raw milk-that is, direct milk preparation as fed, or PLG, or casein, and the from the cow and cooled by standing at room anaphylactic sensitivity was observed. The reactions temperature-was fed to the guinea-pigs and proved are shown in Table 2. to be sensitising to all the animals which drank it.