AOAC 2018 Methods

Items ( g )–( l ) are supplied in the Fructan Assay Kit (Cat. mo. K-FRUC) available from Megazyme, Bray Business Park, Bray, County Wicklow, Ireland, but preparations of enzymes and standards which meet these criteria may also be used.

E. Safety Considerations

The general safety measures that apply to all chemical substances should be adhered to. For more information regarding the safe usage and handling of the fructan assay kit please refer to the associated SDS that is available from the Megazyme website; www.megazyme.com. Sodium borohydride releases hydrogen on contact with water and is extremely hazardous in terms of skin or eye contact. The analyst should wear safety gloves and glasses when weighing this chemical and refer to the appropriate SDS.

F. Preparation of Test Materials

All products should be equilibrated to room temperature (22°C) before they are weighed.

( a ) Test samples .—For dry food, animal feed or grass samples, grind ca 50 g of sample in a grinding mill to pass 0.5 mm sieve. Transfer all material into wide-mouthed plastic jars and mix well by shaking and inversion. For wet products such as canned pet foods, homogenise samples with a Waring blender and freeze-dry approximately 100 g. Analyse a representative sample of the dry product. Record sample wet weight and dry weight. (b) Fructose standard working solution .—Add 0.2 mL fructose standard stock solution [1.5 mg/mL, D(l)] to 0.9 mL acetate buffer, D(b), and mix thoroughly. Dispense 0.2 mL aliquots of this solution (containing 54.5 µg fructose) in quadruplicate to the bottoms of 4 glass test tubes, C(d). Add 0.1 mL acetate buffer, D(b), to each tube. Immediately before incubation in boiling water bath, add 5.0 mL PAHBAH working reagent, D(c) (3).

(c) Reagent blank .—Transfer 0.3 mL acetate buffer, D(b), into test tubes and proceed with the standard assay procedure from G(c)( 3 ).

(d) Sucrose control powder . —Containing ca 10% w/w sucrose. Extract and analyse 400 mg of this powder as per G(a)( 1 ). This product contains no fructan and is used to check the effectiveness of the sucrase and borohydride treatments. The calculated fructan content should be less than 0.3% w/w.

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