Heat-induced formation of N,N-dimethylpiperidinium (mepiquat) in Arabica and Robusta coffee.

N,N-dimethylpiperidinium (mepiquat) is a new process-induced compound formed from natural constituents during the cooking process. Mepiquat was first found in coffee and cereal products, but its formation mechanism in coffee is still unclear. In the current study, Arabica and Robusta coffee beans were roasted at different temperatures (215, 220, and 230 °C) to study the effect of roasting process on mepiquat formation. The highest mepiquat content, 1,020 µg/kg, was found in dark roast (230 °C) Indonesia Wahana, while 430 µg/kg of mepiquat was detected in medium roast (220 °C) Vietnam Robusta. At the same roasting temperature, higher level of mepiquat was observed in Arabica than in Robusta. In both species, substances related to mepiquat formation, including betaine, choline, trigonelline, lysine, carnitine, pipecolic acid (PipAc), pipecolic acid betaine (PipBet), were also detected. The lysine-based Maillard reaction and decarboxylation in Arabica and Robusta promoted mepiquat formation through the degradation of choline and trigonelline, and the formation of intermediate products. Results from both the model system and selected commercial beans showed that choline and trigonelline had a significant correlation (P < 0.01) with mepiquat formation in Arabica. PRACTICAL APPLICATION: Mepiquat is considered as a new process-induced compound resulting from typical roasting conditions, but its formation mechanism in coffee is still unclear. This work demonstrates the formation mechanism of mepiquat by many precursor substances contained in Arabica and Robusta. It is very important to figure out how mepiquat is ''naturally" present in daily diets, especially in those processed at high temperatures.

Li X ，Zhang X ，Tan L ，Yan H ，Yuan Y ... -  《-》

N,N-dimethylpiperidinium (mepiquat) Part 2. Formation in roasted coffee and barley during thermal processing.

Wermann S ，Theurillat V ，Verzegnassi L ，Hofmann J ，Kuchenbecker R ，Constable A ，Delatour T ，Stadler RH ... -  《-》

Homostachydrine (pipecolic acid betaine) as authentication marker of roasted blends of Coffea arabica and Coffea canephora (Robusta) beans.

The occurrence of pipecolic acid betaine (homostachydrine) and its biosynthetic precursor N-methylpipecolic acid was detected for the first time in green coffee beans of Robusta and Arabica species. The analyses were conducted by HPLC-ESI tandem mass spectrometry and the metabolites identified by product ion spectra and comparison with authentic standards. N-methylpipecolic acid was found at similar levels in green coffee beans of Robusta and Arabica, whereas a noticeable difference of homostachydrine content was observed between the two green coffee bean species. Interestingly, homostachydrine content was found to be unaffected by coffee bean roasting treatment because of a noticeable heat stability, a feature that makes this compound a candidate marker to determine the content of Robusta and Arabica species in roasted coffee blends. To this end, a number of certified pure Arabica and Robusta green beans were analyzed for their homostachydrine content. Results showed that homostachydrine content was 1.5±0.5mg/kg in Arabica beans and 31.0±10.0mg/kg in Robusta beans. Finally, to further support the suitability of homostachydrine as quality marker of roasted blends of Arabica and Robusta coffee beans, commercial samples of roasted ground coffee blends were analyzed and the correspondence between the derived percentages of Arabica and Robusta beans with those declared on packages by manufacturers was verified.

Servillo L ，Giovane A ，Casale R ，Cautela D ，D'Onofrio N ，Balestrieri ML ，Castaldo D ... -  《-》

Identification of nutritional descriptors of roasting intensity in beverages of Arabica and Robusta coffee beans.

Bicho NC ，Leitão AE ，Ramalho JC ，De Alvarenga NB ，Lidon FC ... -  《-》

Heat-induced formation of mepiquat by decarboxylation of pipecolic acid and its betaine derivative. Part 1: Model system studies.

This study describes, for the first time, the role of pipecolic acid betaine and pipecolic acid, naturally present in some foods, in the formation of the plant growth regulator N,N-dimethylpiperidinium (mepiquat) under dry thermal conditions. The formation of mepiquat and intermediate compounds was investigated in model systems using high performance liquid chromatography-quadrupole/time-of-flight mass spectrometry. Mepiquat is released with a yield of up to 0.66mol% after thermal treatment (>150°C) of pipecolic acid betaine. Similar conversion rates are attained with the congener piperidine-2-carboxylic acid (dl-pipecolic acid), albeit in the presence of alkylating agents, such as choline, glycine betaine or trigonelline, that are fairly widespread in food crops. These new pathways to mepiquat indicate that the occurrence of low levels of this thermally induced compound is probably more widespread in processed foods than initially suspected (see Part 2 of this study on the occurrence of mepiquat in selected foodstuffs).

Yuan Y ，Tarres A ，Bessaire T ，Stadler RH ，Delatour T ... -  《-》