Freshness of food

Household -based sensors for food/water/environmental monitoring, e.g., quality evaluation of drinking water, freshness of foods in fridge, etc. 

Maintaining the freshness of food as it goes from market to the table is accomplished through chemicals and other substances that act as preservatives, processes that prevent or delay food spoilage, and packaging that guards against the chemical reactions that initiate decay. 

Chan, S. T., M. W. Y. Yao, Y. C. Wong, T. Wong, and C. S. Mok. 2006. Evaluation of chemical indicators for monitoring freshness of food and determination of volatile amines in fish by headspace solid-phase microextraction and gas chromatography-mass spectrometry. Eur. Food Res. Technol. 224 67-74. 

Section 1 Water-Absorption Sheet for Maintaining Freshness of Foods... 

A sheet that absorbs dripping water or moisture from foods is not sufrieient to preserve the freshness of foods. Additionally, as an approach to prevent health problems eaused by baeteria on foods, an antibacterial funetion is often desired for food-related materials. Based on these needs, multifunctional packaging materials, with antibaeterial and deodorant abilities, in addition to a water-absorption function for freshness preservation, are being developed. These new packaging materials will be introduced in what follows. 

The aforementioned powdery inorganic antibacterial agent is easy to use and safe. However, the antibacterial effect can only reach the contact surface of the food. Instead, wasabi extract, which easily vaporizes and the gas surrounds the food, is being tested as an antibacterial agent. Wasabi extract consists of allyl isothiocyanate and is obtained either naturally or synthetically. As this material is permitted by the Department of Health and is currently used to prolong the freshness of foods, safety is not an issue. The basic structure of a sheet utilizing this material is shown in Fig. 2. 

Nuts are rich in protein and fat most commercially important nuts supply about 28 MJ /kg (6600 kcal/kg) of kernel, more than most other foods (Table 2) cereals supply about 15 MJ /kg (3640 kcal/kg) meats about 7.5 MJ /kg (1790 kcal/kg) and fresh fmits less than 2.8 MJ /kg (660 cal/kg). The energy content in kilojoules (1 food calorie or cal = 4.184 kJ) per kilogram of food is calculated by the following formula ... 

Handling conditions must be hygienic. Some types of food, such as milk, can be kept sealed within the processing system. If the food will be exposed to the air during handling, the conditions of the surrounding air - in terms of temperature, humidity and cleanliness - must be the best that can be maintained. This is especially the case with fresh meats. 

Food typically is a complicated system with diverse interfaces. Stable air-water or oil-water interfaces are essential for the production of food foams and emulsions. Interface phenomena, therefore, attract great interest in the food industry. AFM provides enough resolution to visualize the interface structures, but it cannot be directly applied on air-liquid or liquid-liquid interfaces. Fortunately, the interface structure can be captured and transferred onto a freshly cleaved mica substrate using Langmuir-Blodgett techniques for AFM scan. Images are normally captured under butanol to reduce adhesion between the probe and the sample. Then, sample distortion or damage can be avoided (Morris et al, 1999). 

Quality of food products and the ability to guarantee the quality of a food product is becoming increasingly important in a global economy where there are multiple sources for the food product. This need to measure, control and guarantee quality has resulted in an emphasis to develop more analytical techniques/sensors to measure a product for both external and internal quality. Consider quality evaluation of fresh fruits and vegetables. 

U.S. Energy Research and Development Administration. 1977. Plutonium and americium concentration along fresh-water food chains of the Great Lakes, U.S.A. Woods Hole, MA U.S. Energy Research and Development Administration. COO-3568-18. 

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