This study demonstrates how magnetic resonance imaging can be used to quantitate the heating of commercially available baby foods as sold in glass jars either 'on-line' during immersion in warmed water in the scanner's magnet, or 'off-line' following microwave heating. The internal temperature distribution can be measured in 2 or 3-dimensions with a precision of ±1.5 °C compared with fibre optical thermo-probe measurements. Illustrative examples include jars of Heinz 'Banana & Apple', Sainsbury's 'Organic Banana Rice Pudding' & Cow & Gate 'Organic Roasted Vegetable Lasagne.' Localised thermal lags induced by pieces of vegetable in the lasagne were observed during on-line immersion heating. Importantly, the spatially heterogeneous heating by microwaves demonstrates the need for strong warnings about using microwave ovens for heating baby foods.
