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The enzyme-linked immunosorbent assay (ELISA) offers many advantages for the detection of potentially hazardous allergenic food residues that might become adventitious components of other foods during the course of food production and processing. ELISAs detect proteins, and food allergens are proteins. ELISAs are sufficiently sensitive and specific for detection of food allergen residues. ELISAs can also be produced in formats that are compatible with the industrial food processing environment. However, ELISAs also have disadvantages that should be carefully evaluated and widely recognized. Various food-processing operations can have profound effects on the detectability of allergenic food residues. ELISAs detect intact proteins but protein hydrolysates evade detection in some ELISA formats. The residual proteins present in some ingredients derived from commonly allergenic sources may also not be easily detected with ELISAs because of the nature of the protein residues remaining, e.g. lipophilic. Processing operations can dramatically lower the solubility of proteins. In some food formulations, heat processing, in particular, induces chemical modifications that can affect antibody binding to epitopes in the ELISA. The use of naturally incurred standards where allergenic food residues are incorporated into various representative food matrices and then processed in a manner similar to "real-world" food processing can reveal some of the limitations of allergen ELISAs. Methods for the preparation of naturally incurred standards in chocolate, cookie, muffin, ice cream, pasta, frankfurter, and cream of potato soup are provided as examples.

Supercritical carbon dioxide extraction was investigated for removal of cholesterol and lipid components from dried egg yolk. Four different combinations of pressure and temperature were used including 163 atm/rlO"C, 238 atm/45"C, 306 atm/45"C and 374 atm/55"C. As temperature and pressure were increased, more lipids and cholesterol were removed. Extraction at 306 atm/45"C or 374 atm/55"C removed approximately two-thirds of the cholesterol. Phospholipids and protein were concentrated under the supercritical extraction conditions used. Sponge cake volume was significantly (PcO.05) improved at extraction conditions of 163 atm/llO"C, 238 atm/45"C and 306 atm/45"C, which may have been due to higher phospholipid and protein concentrations. Onlv extraction at 374 atm/55"C significantlv fP

Supercritical carbon dioxide (SC-CO2) was used to extract cholesterol and other lipids from dehydrated beef powders and chunks. When powders were extracted at 55 O C and a fluid density of 0.90 g/cmB, the cholesterol and total fat contents of the product could both be reduced by as much as 87 % . Lipids were more easily extracted from chunks than from powders, allowing for successful removal at lower temperatures and pressures. Extracted samples were lighter in color than the control. The residual lipids in the extracted samples also contained higher relative percentages of linoleic and linolenic acids than did the lipids in the control samples. Taste panel evaluation of control and extracted powders found no significant differences in beef flavor, the presence of off-flavors, or overall acceptability.

Enzyme-linked immunosorbent assay (ELISA) is a commonly used method for the detection of trace amounts of potentially allergenic protein residues in foods. However, food matrices and processing conditions can affect the detection of protein residues. The effects of acidity on the detectability of several allergenic proteins commonly found in salad dressing using ELISAs was investigated. First, recovery experiments were performed on salad dressing formulated with 0 to 1000 ppm mustard flour (mustard). The mean percent recovery for mustard from the salad dressing was only 7.7%+/- 1.6%. When the pH of the salad dressing was adjusted to pH 7 prior to spiking with mustard, recovery improved to 94.1%+/- 7.6%. However, if the pH was adjusted to pH 7 after spiking and extraction, the recovery was only 11.1%+/- 1.7%. When vinegar was spiked with mustard flour at pH 3, 3.5, and 4, detectability of mustard was lowest at pH 3. Basic extraction of mustard proteins from salad dressing did not improve the mustard detection. Acidic salad dressing matrices reduced the detectability of mustard by the mustard ELISA probably because of acid precipitation of mustard proteins that renders them insoluble and nonextractable. Commercial salad dressings containing 100 ppm (mg/kg) of egg, milk, or gluten were analyzed every 2 to 4 d for 90 d using 3 commercially available ELISAs. A decrease in the detection of the egg, milk, and gluten in the salad dressing upon storage was observed. Our study highlighted the importance of evaluating the utility of various ELISAs for specific food matrices and the recovery as a function of product storage.

Tree nuts, including walnuts, can be responsible for allergic reactions. Food manufacturers have the responsibility to declare the presence of walnuts on packaged foods even when trace residues may be present from the use of shared equipment or the adventitious contamination of ingredients. The aim of this study was to develop a rapid, sensitive, and specific enzyme-linked immunosorbent assay (ELISA) method for the detection of walnut protein residues. Mixtures of raw and roasted English walnuts of several varieties were defatted, powdered, and used as separate antigens in sheep and New Zealand white rabbits. An ELISA was developed using the sheep antiroasted walnut serum as the capture reagent and rabbit antiroasted walnut serum as the detector reagent followed by addition of commercial goat anti-rabbit IgG antibody labeled with alkaline phosphatase and subsequent substrate addition. The performance of the ELISA was validated by testing known amounts of walnut (0 to 100 ppm) either spiked into or manufactured into milk chocolate, cookies, muffins, or ice cream. Recoveries of 1 to 100 ppm walnut-in-chocolate ranged from 71.6% to 119%+/- 7% to 16.5%. The walnut ELISA has a detection limit of 1 ppm (1 microg/g) walnut in several food matrices. Substantial cross-reactivity was observed with pecan while minimal cross-reactivity was noted for hazelnut, mustard, mace, and poppy seed among almost 100 foods and food ingredients tested. This walnut ELISA can be used to detect undeclared walnut residues in foods and ingredients and as a tool to validate the effectiveness of allergen control programs for walnuts.

Supercritical carbon dioxide (SC-CO2) extraction was studied for removal of lipids and cholesterol from dried chicken meat powder and chunks. Two combinations of pressure and temperature were used: 299 atm and 45 C, and 381 atm and 55 C, both providing a fluid density of .90 g/cm3. For a given quantity of CO2, at the higher temperature and pressure, significantly (P < .05) more lipids and cholesterol were extracted from the powder. At 381 atm and 55 C, approximately 89% of the lipids and 90% of the cholesterol were removed from the dehydrated chicken meat powder. With respect to the chunk chicken meat, about 93% of the lipids and 82% of the cholesterol were extracted at 299 atm and 45 C. It seemed that the SC-CO2 extraction process was more efficient when chunks were used. Protein was concentrated as cholesterol and lipids were removed by SC-CO2 extraction of both chicken meat types, and Hunterlab L values increased but aL values decreased, indicating a lighter color with less redness. This research indicated that SC-CO2 extraction holds promise for substantially reducing lipids and cholesterol in chicken meat.