Core temperature in fish cakes

The paper “On-line and non-destructive measurement of core temperature in heat treated fish cakes by NIR hyperspectral imaging” authored by Jens Petter Wold has been published in Innovative Food Science and Emerging Technologies.


During industrial heat treatment of food products the core temperature is a critical control parameter with respect to food quality and in particular food safety. This paper presents a method based on near-infrared (NIR) spectroscopy that enables on-line and non-contact monitoring of the complete product volume on a typical industrial belt cooking system. Two NIR systems (760–1040 nm) were evaluated on heat treated fish cakes, one point measurement system and one hyperspectral imaging system. Both systems measured several millimetres into the product. Core temperature in the fish cakes (at 10 mm depth) varied between 53 and 99 °C. The point system performed best with a root mean square error of prediction of 2.3 °C, while the imaging system was less accurate with an error of 4.5 °C. It was demonstrated that temperature changes down to 11–13 mm depth in the fish cakes could be registered by the NIR point system.

Industrial relevance: During industrial heat treatment of food products the core temperature is a critical control parameter with respect to food quality and in particular food safety. Especially for ready-made products this is important since they can be consumedwithout further heat treatment. Today,most temperature measurements during processing are typically based on spot checks on a small number of products. The core temperature of heat treated products is usually the most critical and needs to be measured by insertion of thermo couplers. This procedure is insufficient since it leaves the producer with a large degree of uncertainty; only a few products are checked and a very tiny volume of the checked products is actually measured. Due to these limitations, current practise is to over-cook much of the food to ensure that everything has reached the critical core temperature. This might reduce quality of the end product and also requires overspending of energy. In the food industry there is a need for non-contact on-line temperature measurements for improved control of the cooking process. The ideal system should be able to log the temperature in the entire production volume.

The method presented in this article can allow complete monitoring of the heat treated products. In this way the
producer could have full control of the heating process and be sure that sufficient core temperature is reached in all product units. Such a system can also be used to control the temperature to a certain target that ensures safe products of high quality.

DOI: 10.1016/j.ifset.2015.12.012