Carotene and Ascorbic Acid in Foods


 How various procedures affect carotene values when lycopene
is present is depicted in Table 1. A sample of pink guava blended
in ether was extracted 6 times with 90 percent methyl alcohol,
another sample was extracted once, and a third was unextracted.
The 3 samples were then adsorbed on 2 lots of dibasic phosphate.
Extraction with 90 percent methyl alcohol removed a little
lycopene. The 2 lots of phosphate varied slightly in their adsorp-
tive power. The spectral data showed that even after diphasic
separation, adsorption, or both, still almost one-half of the
color in the solution was due to lycopene.

 TABLE 1.-CAROTENE VALUES IN PINK GUAVAS AFTER DIFFERENT
 EXPERIMENTAL PROCEDURES.
 Carotene found after adsorption on 2
 different lots of dibasic calcium phos-
 phate, computed from absorption data
 Treatment of Sample at:
 I 450 Millimicrons 1450/505 Millimicrons
 Lot 1 Lot 2 Lot 1 Lot 2
 Microgms Microgms Microgms Microgms
Extracted 6 times with 90%
 MeOH before absorption---............ 5,440 5,100 2,960 2,750
Extracted once with 90% MeOH
 before absorption ...................... 5,500 5,260 3,070 3,070
No extraction ....................... ... 5,600 5,280 3,120 2,990

 In routine work with the spectrophotelometer an exit slit of
5 millimicrons was used, but when pigments other than carotene
were present a 2.5 millimicron slit was substituted. In both
cases the 0.5 mm entrance slit was employed. The total spectral
regions isolated in each case were 7.0 and 4.5 millimicrons,
respectively.
 Ascorbic Acid.-The volumetric determination of ascorbic acid
with Tillman's indicator, or sodium 2,6 dichlorobenzenoneindo-
phenol, has been used general (3). At first 8 percent
CC13COOH was the extracting medium, but later 2 percent
HPO was used (9). In special cases where the amount of
ascorbic acid to be determined was small, or color interfered with
the endpoint of the titration, either the photometric (1) or
electrometric (4) procedure was used as alternate. These 3
methods were in agreement when used on the same samples.
 When titration values were unusually large or suspected, con-
 firmation was obtained by checking on the destruction of the
 titration values by an oxidase prepared either from squash (12)