Quantitation of chlorophylls and 22 of their colored degradation products in culinary aromatic herbs by HPLC-DAD-MS and correlation with color changes during the dehydration process.

Chlorophylls and their green and olive-brown derivatives were successfully separated from culinary herb extracts by HPLC with photodiode-array and mass spectrometry detection. The method involved a ternary gradient elution and reverse-phase separation conditions capable of resolving 24 different pigments (2 chlorophylls and 22 of their derivatives) of different polarities within 28 min. The method was applied to monitor color changes in 50 samples of culinary aromatic herbs subjected to five different drying treatments. Of the 24 pigments, 14 were key to understanding the differences between the primary degradation pathways of chlorophyll a and chlorophyll b in culinary herbs during drying processes. A color degradation ladder based on the total molar percentage of all the remaining green pigments was also proposed as a tool to measure the impact of drying treatments on aromatic herb visual aspects.

Determination of added sulfites in dried garlic with a modified version of the optimized Monier-Williams method.

The optimized Monier-Williams method is slightly modified so that it could be applied for determining sulfite content in dried garlic. Dried garlic sample is directly acidified in a reactor at a pH below 3. At this pH level, the alliinase enzyme activity is irreversibly blocked, and the sulfur-containing amino acids such as alliin (the most abundant) present in dried garlic cannot be transformed into corresponding thiosulfinates such as allicin, which is absent in dried garlic. This prevents allicin from reacting with added sulfites and being probably converted to S-allyl thiosulfate, which is not volatile and has no taste. It is found that at a pH below 2.4 and at boiling water temperature, allicin produces sulfur dioxide in adequate quantity to explain the false-positive results when utilizing the optimized Monier-Williams method with allicin suppression for unsulfited dried garlic samples. Finally, when garlic samples are stabilized in a phosphoric acid buffer at a final pH around 2.4, no sulfite is produced during the Monier-Williams distillation, which is further proof there are no naturally occurring sulfites in unsulfited dried garlic under these mild conditions.