Cheng Janice, Omolo Morrine, Flores-Sanchez Cecia, Ubbink Job
Department of Food Science and Nutrition, University of Minnesota, St. Paul, Minnesota, USA.
J Food Sci. 2025 Aug;90(8):e70385. doi: 10.1111/1750-3841.70385.
The aim of this research is to determine if low-cost devices can be used to accurately and reproducibly measure water activity (a). Small-scale food producers, including those in the cottage food industry and start-up companies, need affordable devices to accurately measure the a of their food products. Water activity plays a critical role in food safety and quality, and products must meet a predefined legal requirement (a ≤ 0.85). In this project, devices ranging from <$100 to ∼$2000 were tested against four criteria: (1) robustness in a stress test; (2) reproducibility; (3) equilibration time; and (4) accuracy. The performance of the devices was investigated by measuring the water activity of six saturated salt solutions (0.11 < a < 0.94 at T = 22°C ± 1°C). Linear regression models were developed for each device and implemented in Excel to give corrected values ± standard deviations. For one of the types of low-cost devices, seven more devices were tested to determine consistency among devices from the same manufacturer and brand. Devices were found to be suitable for a measurements for food safety if the corrected values were consistently close to the actual a-values of the saturated salt solutions and if the maximum error was lower than 0.005 (ISO 18787). Of the seven types of low-cost devices tested, none strictly met all conditions, but four were found to be sufficiently close to allow for use by cottage food producers for directional testing, provided that samples are also sent for lab testing.
本研究的目的是确定低成本设备是否可用于准确且可重复地测量水分活度（a）。包括家庭食品工业中的生产商和初创公司在内的小规模食品生产商需要价格实惠的设备来准确测量其食品的水分活度。水分活度在食品安全和质量方面起着关键作用，产品必须符合预定义的法律要求（a≤0.85）。在本项目中，对价格从低于100美元到约2000美元不等的设备依据四个标准进行了测试：（1）压力测试中的稳健性；（2）可重复性；（3）平衡时间；以及（4）准确性。通过测量六种饱和盐溶液（在T = 22°C±1°C时，0.11 < a < 0.94）的水分活度来研究这些设备的性能。为每种设备建立了线性回归模型，并在Excel中实施以给出校正值±标准偏差。对于其中一种低成本设备类型，又测试了另外七台设备，以确定同一制造商和品牌的设备之间的一致性。如果校正值始终接近饱和盐溶液的实际a值，并且最大误差低于0.005（ISO 18787），则认为这些设备适用于食品安全的a测量。在所测试的七种低成本设备类型中：没有一种完全满足所有条件，但发现有四种足够接近，只要也将样品送去实验室检测，家庭食品生产商就可以将其用于定向测试。
