EXAMINATION OF THE EFFECT OF DOMESTIC COOKING ON ACRYLAMIDE LEVELS IN FOOD Rachel Burch Leatherhead Food International

Objectives To compile a list of foods relevant to home cooking that are high in asparagine, taking into account levels of consumption To examine the effect of cooking on acrylamide levels of less complex foods (i.e. vegetables) To examine varietal effects in potatoes

Total quantities (grams) of vegetables and vegetable products consumed in 7 days (consumers only) Type of food Total quantities (grams) consumed in 7 days MeanMedian% consumers Green beans Leafy green vegetables Carrots – not raw Tomatoes – not raw Other vegetables Potatoes Potato chips Other fried/roast potatoes and products Potato products – not fried Other potatoes and potato dishes NDNS data, 2002

Asparagine and glutamine levels Asparagine mg/100g fresh weight Glutamine mg/100g fresh weight Carrots Tomatoes16.6 Onions33-55 Cauliflower740 Mushrooms12-17 Broccoli716 Green bean pods1875 Kale16107 Spinach639 Potatoes13394

Task 3a Potatoes cooked from fresh and from frozen –Baked, boiled, roast, saute, microwave “baked” from fresh –Boiled, roast, saute from frozen Onions cooked from fresh and from frozen –Boiled, baked, fried from fresh and frozen

Task 3a – Potatoes

Task 3a – Onions

Task 3c – Cyclic re-use of frying oils Five different oil types Five cookings in each oil –Initial cookings to same colour, to determine fry time for each oil. Subsequent cookings for the same length of time –Oil temperature 190ºC (except lard: 175ºC)

Use of different cooking oils

Re-use of cooking oils

Re-use of cooking oils - conclusions Preliminary data suggests: –Some differences in acrylamide levels in chips cooked in different oils –Some indication that acrylamide levels increase in chips cooked in re-used rapeseed oils

Task 3d – Effect of pre-treatment Chips –Washing, storing in water for 30 mins, storing in water for 2 hours –Samples prepared in triplicate, chips cooked for same length of time Roast potatoes –Washing, storing in water for 30 mins, storing in water for 2 hours, par-boiling –Samples prepared in triplicate, cooked for same length of time except for par-boiled

Task 3d – Effect of pre-treatment - Chips

Chips – correlation with colour greenred

Chips – correlation with colour L Value DarkLight

Pre-treatment – Chips – glucose removed

Task 3d – Effect of pre-treatment – roast potatoes

Pre-treatment – roast potatoes – glucose removed

Effect of variety - chips

Effect of variety – Roast potatoes

Effect of variety – baked potatoes

Conclusions – factors affecting acrylamide formation in domestic cooking Type of cooking –Acrylamide formed in roasted, sautéed, oven baked potatoes, higher levels found in potatoes cooked after freezing –Not formed in boiled or microwaved potatoes –Formed in fried onions, onions baked from frozen –Not formed in onions baked from fresh, or boiled Pre-treatments –Soaking for two hours, or par-boiling led to greatest reductions –Indication that some pre-treatments affect fat content

Conclusions – factors affecting acrylamide formation in domestic cooking Chip colour correlates to acrylamide levels, roast potato colour does not –Roast potatoes were not of uniform size and shape Variety –Some varieties result in higher acrylamide levels relative to other varieties cooked using the same method