No abstract

No abstract

A quantitative study has been made of changes in oxygen content, ascorbic acid content, flavour and colour during the processing and storage of pasteurised and frozen orange juices. By means of a gas‐saturation procedure, the juices were canned with initial oxygen contents ranging from about 3.5% to less than 0.002%. In frozen juices stored at o° F the presence of free oxygen in the cans for at least one year permitted slow oxidative loss of ascorbic acid. In pasteurised juices stored at 86° F, oxidative destruction of ascorbic acid occurred only during the first few days, since free oxygen rapidly disappeared from the cans. Throughout subsequent storage anaerobic loss of ascorbic acid continued at a rate about one‐tenth of that in the early period. Anaerobic reactions also contributed to flavour changes in pasteurised orange juices since complete removal of oxygen failed to retard the development of stale flavour at 86° F.

A method is presented for the determination of limonin, the bitter principle of oranges, based upon selective extraction and conversion to the dinitrophenylhydrazone, which is separated by thin‐layer chromatography for estimation by spectrophotometry. The method can be used as a routine procedure for the study of variations in the limonin content of oranges and processed juices. Some examples are given of its application to the study of the problem of bitterness in orange juice.

Polyamides are shown to be effective adsorbents for removal of the bitter principle, limonin, from pasteurised Washington Navel orange juice. The extent of limonin removal varies with different juices, but sufficient can be removed by one or two treatments to bring the concentration below the organoleptically detectable level. The commercial use of polyamides to prepare non‐bitter juices from Navel oranges is discussed.