A GUIDE TO CAROTENOID ANALYSIS IN FOODS

40 A Guide to Carotenoid Analysis in Foods
Francisco), which were chosen to represent three
distinct regions (northeast, north central, and west).
For each tomato product, analyses were performed
on at least one name-brand and one store-brand product
from each of the three cities. For tomato soup,
for example, at least two units of a name brand (having
the same lot number) and two units of a store
brand (having the same lot number) were obtained
from each of the three cities. Name-brand or storebrand
products having the same lot number were
combined. Aliquots from the resulting six samples
were then analyzed.
To investigate the effects of influencing factors,
sampling has to be so designed that variables are
controlled. For example, to verify cultivar differences
and seasonal variation in the carotenoid composition
of kale, mature leaves of each of two cultivars were
hand-picked at random from the same farm, thus
stage of maturity and environmental conditions were
the same for both cultivars (Mercadante and
Rodriguez-Amaya 1991). Ten sample lots (laboratory
sample: about 250 g each) were collected and
analyzed individually for each cultivar for each season,
the lots being harvested at the same time (morning)
at different days during the season. One sample
lot each of the two cultivars was collected at each
sampling day. At the laboratory, the leaves were finely
cut and mixed, and 4–5g subsamples were immediately
taken for analysis. To verify the possible effects
of agrochemicals, 10 sample lots of mature kale
were collected during the same time period from
neighboring farms, one natural and the other using
agrochemicals.