Food preservation involves different food processing steps to maintain food quality at a desired level so that maximum benefits and nutrition values can be achieved. Food preservation methods include growing, harvesting, processing, packaging, and distribution of foods. The key objectives of food preservation are to overcome inappropriate planning in agriculture, to produce value-added products, and to provide variation in diet. Food spoilage could be caused by a wide range of chemical and biochemical reactions. To impede chemical and microbial deterioration of foods, conventional and primitive techniques of preserving foods like drying, chilling, freezing, and pasteurization have been fostered. In recent years, the techniques to combat these spoilages are becoming sophisticated and have gradually altered to a highly interdisciplinary science. Highly advanced technologies like irradiation, high-pressure technology, and hurdle technology are used to preserve food items. This review article presents and discusses the mechanisms, application conditions, and advantages and disadvantages of different food preservation techniques. This article also presents different food categories and elucidates different physical, chemical, and microbial factors responsible for food spoilage. Furthermore, the market economy of preserved and processed foods has been analyzed in this article.

Agglutinated blood transports differently onto paper than stable blood with well dispersed red cells. This difference was investigated to develop instantaneous blood typing tests using specific antibody-antigen interactions to trigger blood agglutination. Two series of experiments were performed. The first related the level of agglutination and the fluidic properties of blood on its transport in paper. Blood samples were mixed at different ratios with specific and nonspecific antibodies; a droplet of each mixture was deposited onto a filter paper strip, and the kinetics of wicking and red cell separation were measured. Agglutinated blood phase separated, with the red blood cells (RBC) forming a distinct spot upon contact with paper while the plasma wicked; in contrast, stable blood suspensions wicked uniformly. The second study analyzed the wicking and the chromatographic separation of droplets of blood deposited onto paper strips pretreated with specific and nonspecific antibodies. Drastic differences in transport occurred. Blood agglutinated by interaction with one of its specific antibodies phase separated, causing a chromatographic separation. The red cells wicked very little while the plasma wicked at a faster rate than the original blood sample. Blood agglutination and wicking in paper followed the concepts of colloids chemistry. The immunoglobin M antibodies agglutinated the red blood cells by polymer bridging, upon selective adsorption on the specific antigen at their surface. The transport kinetics was viscosity controlled, with the viscosity of red cells drastically increasing upon blood agglutination. Three arm prototypes were investigated for single-step blood typing.

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Background: In recent years, formaldehyde is reported to be widely used as a food preservative to increase the shelf life of fruits and fishes in tropical countries. Formaldehyde is detrimental to human health. Hence, use of formaldehyde as a food preservative is legally prohibited in most of the countries. To regulate formaldehyde application in foods, the regulatory bodies often conduct on-the-spot analytical tests to detect artificially added formaldehyde in food items. However, formaldehyde is ubiquitous in the environment and is present in many animal and plant species as a product of their normal metabolism. This naturally occurring formaldehyde may interfere in the detection of artificially added formaldehyde in foods. It is, therefore, important to study the concentration and formation mechanism of naturally occurring formaldehyde in food items. Results: In this study, the formaldehyde contents of food samples were determined using spectrophotometric technique. The naturally occurring formaldehyde contents of a wide range of fruit, vegetable, milk, poultry, mutton and meat samples were determined. In addition, formaldehyde contents of processed food items, such as: cooked beef and poultry, beverages, and commercially available UHT milk and powdered milk samples, were also assessed and analyzed. The naturally occurring formaldehyde contents of fruit, vegetable, milk, poultry, mutton and meat samples were found up to 58.3, 40.6, 5.2, 8.2, 15.2 and 8.5 ppm, respectively. Formaldehyde contents of commercially available UHT milk, powdered milk, beverages, cooked beef and poultry were found up to 187.7, 194.1, 21.7, 4.3 and 4.0 ppm, respectively. This study also analyzed the time dynamic behavior of the formation of endogenous formaldehyde content of banana (AAB genome of Musa spp.), mandarin and beef. Conclusions: The experimental results provide a baseline data of natural occurring formaldehyde content of the analyzed food items. The formation behavior of formaldehyde may vary according to food types, storage temperature, storing time, and aging pattern of the food items. The findings of this study will be useful for the consumers, researchers, legal authorities and other stakeholders working on food safety and preservation.

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Urinary or serum uric acid concentration is an indicator of chronic kidney condition. An increase in uric acid concentration may indicate renal dysfunction. Reliable instantaneous detection of uric acid without requiring sophisticated laboratory and analytical instrumentation, such as: chromatographic and spectrophotometric methods, would be invaluable for patients with renal complication. This paper reports the early development of a simple, low-cost, instantaneous and user-friendly paper based diagnostic device (PAD) for the qualitative and quantitative detection of uric acid in urine. A colorimetric detection technique was developed based on the intensity of Prussian blue color formation on paper in presence of uric acid; the reaction rate of corresponding chemical reactions on paper surface was also studied. Based on the colorimetric signal produced on paper surface, a calibration curve was developed to detect unknown concentration of uric acid in urine. The effect of temperature on formation of color signal on paper surface was also analyzed. In this study, estimation of urinary uric acid using MATLAB coding on a windows platform was demonstrated as the use of software application and digital diagnostics. This paper-based technique is faster and less expensive compared to traditional detection techniques. The paper-based diagnostic can be integrated with a camera of smart phone, tablet computer or laptop and an image processing application (using windows/android/IOS platform) as a part of digital diagnostics. Therefore, with proper calibration, the paper-based technique can be compatible and economical to the sophisticated detection techniques used to detect urinary uric acid.

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