Citrus juice characterization. Analysis of the phosphorus fractions

Abstract

The organic and inorganic phosphorus compounds of orange, lemon, and grapefruit juices were fractionated into groups of total P, inorganic P, lipid P. and a n ethanol-insoluble P fraction which contains nucleic acids and phosphoproteins. The averages of total P for orange, lemon, and grapefruit juices were 19.3, 11.1, and 13.6 mg. of P per 100 ml., respectively. The average percentages of total P distributed among these groups for the three juices were, respectively, 65.3, 55.0. and 69.5 for inorganic P; 7.3, 11.6, and 7.9 for lipid P; and 15.6, 17.5, and 11.0 for ethanol-insoluble P. A n inverse correlation was observed between the percentages of inorganic P and ethanol-insoluble P of all juices, but particularly orange.

Identification and analysis of the major acids from fruit juices and wines

“…In the case of grape juice the inorganic phosphate represents over 90% of the total phosphorus present, i.e., the P is largely in the PO43-form and little is combined in organic forms. Such a relationship was also found with orange juice (Vandercook and Guerrero, 1969). In comparing the merits of the two methods it is to be noted that the glc procedure also gives information about the amounts as well as the kinds of other acids present in the sample.…”

“…As a simple method was available to measure the inorganic phosphate content of juices and wines by glc, a comparison was made between this method and the molybdenum blue method for phosphorus. The latter has been described by Vandercook and Guerrero (1969), the only modification being, in the case of digestion for mea- Apple juice 7.7 7.5 6.0 5.7 5.9 5.6 6.6 7.9 7.5 6.6 6.3 6.2 surement of the total phosphorus, the sample was subsequently neutralized to pH 8.2. Results for these two methods for apple and grape juices are given in Table IV and are reported as elemental phosphorus.…”

“…Phosphoric Acid. The phosphate present in juices and wine was measured by the molybdenum blue method both before and after digestion (inorganic and total phosphorus) as described by Vandercook (1969). Ascorbic acid was used as the reducing agent and the absorbance of blue complex was measured at 820 µ.…”

Citrus juice characterization. Identification and estimation of the major phospholipids

“…The total lipid phosphorus content of citrus juices was reported as part of an earlier paper from this laboratory (Vandercook and Guerrero, 1969). This lipid fraction of a citrus juice makes a significant contribution to the color, flavor, and cloudy appearance (Curl and Veldhuis, 1947).…”

“…The purpose of this investigation was to identify and quantitatively measure the major phospholipids of representative orange, lemon, and grapefruit juice samples. EXPERIMENTAL Extraction of the phospholipids followed the procedure reported earlier (Vandercook and Guerrero, 1969) with only minor modifications. Since the phospholipids are labile compounds, all manipulations were carried out as quickly as possible and with evaporation temperatures not exceeding 30°C.…”