AOAC Guidance on FA Immunoassay Validation (August 2023)

remaining ingredients (as appropriate) and processing the food matrix under relevant conditions (baking, heating, etc.). Alternatively, the food allergen can be made into a suspension (suspended in a regular part of the recipe) to be mixed with ingredients in the matrix recipe. 1154 3.6. The actual weight of the incurred matrix material should be weighed throughout preparation, and 1155 in particular before and after processing in order to account for any moisture loss or gain during 1156 processing (grams or kilograms). 1157 3.7. Matrix form considerations 1158 3.7.1. The form of both the matrix and the food allergen material should be considered when 1159 developing a protocol to produce incurred testing materials. Important properties to consider 1160 include particle size, texture (dry, sticky, fluid, etc.), moisture content, etc. 1161 3.7.2. If the matrix (or a component thereof) and the food allergen material have similar properties, 1162 these two materials can likely be blended homogenously. 1163 3.7.3. If the matrix (and all components thereof) and the food allergen material have very different 1164 properties, alternate strategies may be needed to prepare appropriate testing materials. 1165 Below are some examples of how to prepare incurred materials when the food allergen 1166 material and matrix have different properties. Alternatively, an alternate food allergen 1167 material may need to be used. 1168 3.7.3.1. A suspension of the food allergen material can be incorporated more easily into a matrix 1169 with different properties, a uniform suspension of the food allergen material may be 1170 prepared in a fluid and incorporated into the matrix formulation as most appropriate to 1171 achieve a homogeneous mixture. The suspension should be made in a regular part of 1172 the recipe (see also 3.5). 1173 3.7.3.2. Cryo milling with dry ice of paste ingredients can be performed to achieve a consistent 1174 fine powder. 1175 3.7.3.3. Use of liquid nitrogen and a mortar/pestle or spice grinder can turn paste or solid 1176 ingredients to a powder. Note: if using a spice grinder, be mindful to keep materials 1177 from getting too warm. The end product can also be sifted to achieve a fine powder 1178 consistency. 1179 3.7.3.4. A suspension of the food allergen material in water can alternatively be mixed with a 1180 dry matrix (soaking of the dry matrix resulting in a paste-like consistency). A low 1181 concentration allergen material suspension is typically needed to achieve this. The 1182 mixed paste-like material is then dried (with a lyophilizer, speed vac, ventilator, etc.) 1183 and milled. If drying operations are used, careful attention should be paid to the 1184 moisture balance of the system (i.e., moisture content before and after drying) to 1185 correctly calculate the concentration of food allergen material in the dried product. 1186 3.8. Achieving uniform, low concentrations of food allergen material 1187 3.8.1. In general, preparation of incurred matrix batches of at least 1 kg are preferable to facilitate 1188 accurate weighing of food allergen material and to enable thorough mixing with test kitchen- 1189 scale equipment. 1190 3.8.2. Adequate mixing of food allergen materials and matrix materials can be achieved with 1191 kitchen-scale equipment such as stand mixers, food processors, and blenders. Thorough 1192 mixing can also be achieved manually, for example, with a sifter for dry materials. If available, 1193 1152 1153