longer-terms storage is a normal pa

longer-terms storage is a normal part of domestic consumers’
behaviour and laboratories freeze food prior to analysis, in both
cases for convenience.
In general, analytical laboratories and domestic kitchens have
20 C freezers. Whilst laboratories could use 80 C, this equipment
is expensive to purchase and has higher operation costs,
mainly due to the energy consumption. Bearing in mind the sensitivity
of carotenoids, the impact of freezing/storage temperature
may be important, but no studies were found regarding to the effect
of freezing using the same food batch and the measurement
uncertainty to interpret the differences observed. Some researchers
choose to analyse products in the market, and acquired fresh,
frozen or canned fruits and vegetables as available to consumers.
In such cases, analysis of processing effects is difficult since raw
and processed foods cannot be obtained from the same batch,
and the mass fraction/profile of compounds may be different
depending on cultivar, harvest, ripeness, etc. (Dias, Camões, & Oliveira,
2009; Hart & Scott, 1995).
The determination of carotenoids in food by high performance
liquid chromatography (HPLC) requires the use of expensive standards,
often hundreds of euros per milligram. Inevitably, these
compounds degrade (oxidation, structural rearrangement, isomer
formation) during storage. Furthermore, the preparation of working
standard solutions daily, at different concentrations, is not only
expensive but also time consuming.