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In the food safety domain, the respect of the cold chain is of prime importance. The present paper presents an original method to monitor the food cold chain of everyday refrigerated food products sold in self service counters of supermarkets and hypermarkets in France. The proposed method consists in dissimulating a small temperature recorder inside the food product at the end of the production line and to send this product, equipped with the concealed device yet undistinguishable from any other, throughout the supply chains. At the end of the cold chain, the consumer who discovers the recorder is invited to send it back to the laboratory. Three types of products were chosen depending on their recommended conservation temperature, their shape and the logistic circuit they were likely to follow. 480 recorders have sent. A return rate of 65% allows the observation of the complete thermal history observed in 314 food products, representing a sum of more than 3 800 recording days. The results are presented in a qualitative form (degrees of compliance / non compliance of the recommended temperature) as well as a quantitative form (average temperature and residence time of the products in the different links of the cold chain) over the entire cold chain, and for each link of the cold chain. The results indicate that ¾ of the food product are conserved in good / very good temperature conditions, and that 3% of the observations dramatically exceed the recommendations, especially at the last stages of the cold chain.

Control of food processes involving vapor compression cycles as actuators is often a difficult task: indeed this particular device is itself a complex process including coupled unit operations as evaporation, compression, condensation and expansion. Nevertheless, an accurate control of heat transfer rate is often essential for global quality of product and stability of flow in exchangers. Moreover a number of vapor compression systems are already equipped with variable speed‐compressors and fans. However, due to lack of knowledge about the dynamic behavior of these systems, the industry has not taken full advantage of these variable devices to get substantial control performance improvement. This paper presents a lumped‐parameter model for describing the dynamics of vapor compression cycles. Based on moving‐boundary approach for the description of two‐phase/single phase interface inside the heat exchangers, this low‐order model composed of only ordinary differential equations can be highly useful for design of control strategies. This model has been validated on an experimental device and a good agreement between measurements and computed data has been found. Use of this model in food process control design is discussed.

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