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Measuring Dissolved Oxygen in Fruit Juice

Prague (Pressweb) - Ascorbic acid, commonly known as vitamin C, is an essential organic compound used extensively in the food industry. As a natural antioxidant, ascorbic acid aids in iron absorption and functions as an enzymatic electron donor, reducing proximate oxygen. By reducing the amount of oxygen in its immediate environment, ascorbic acid effectively inhibits the production of free radicals. It is found naturally in many fruits, but is usually added during the production and storage of fruit juice products to improve palatability, aesthetics, and increase nutritional value. In the storage of juice, ascorbic acid can degrade over a period of time due to the presence of dissolved oxygen.

This degradation can occur over hours or weeks depending on conditions such as temperature, light, packaging permeability, and pH. Eventual oxidation of ascorbic acid and other chemical species can lead to the formation of brown-colored pigments in a juice product. Ascorbic acid degradation due to dissolved oxygen not only affects the aesthetic properties of a juice, but it can act as a precursor to the formation of unwanted aldehydes, which affect its aroma and flavor. Several methods can be employed to reduce the amount of dissolved oxygen present in storage containers, such as vacuum-deaeration, gas sparging, and membrane deaeration. By understanding the dissolved oxygen content of fruit juices, manufacturers can improve overall product quality.

An orange juice producer was interested in monitoring a variety of parameters including pH, temperature, and dissolved oxygen of their finished juice products. They were particularly concerned with the dissolved oxygen concentration values with respect to product packaging material; they considered that the permeability of their juice container could affect the dissolved oxygen concentration over time. The customer was looking to relate the shelf life of their juice product to the dissolved oxygen concentration during refrigeration, storage, and temperature variations associated with the shipping and distribution cycle. Their initial experiments would monitor juice product in various packaging materials over different temperature ranges for a period of several weeks; their final experiments would monitor juice product as it moved through shipping and distribution. The customer was ultimately looking for a portable and reliable device for measuring dissolved oxygen in their juice containers.

Hanna Instruments recommended the waterproof HI98186 Portable Dissolved Oxygen Meter. The customer wished to maintain low head-space in their containers to reduce exposure to the sample when opening the container for analysis. For this concern, Hanna provided the HI76407/4 Polarographic Dissolved Oxygen Probe, without the protective sleeve. The HI76407/4 is the same as the HI76407/4F probe but without the threads for protective sleeve. The HI76407/4 tapered design allows for a form fit between the probe and the container minimizing the amount of air entering into the sample during analysis. The customer appreciated that the local office was able to accommodate their specific needs by changing the I76407/4F probe for the HI76407/4 version.

All readings taken were automatically compensated for barometric pressure and temperature. The customer liked the log-on-demand function, allowing them to record up to 400 dissolved oxygen samples and aiding in the speed of the overall data recording. The customer also liked that the data could be transferred from the meter to a PC using the HI920013 USB cable and HI92000 software. Overall, the customer felt that the HI98186 met all of their needs, and appreciated that the meter was supplied with all the accessories including spare membranes, fill solution, and a hard shell carrying case.