The challenge of o-phenylphenol detection in coffee: How "OPP-conjugates" hide their presence in green and roasted samples.

o-Phenylphenol (OPP) is not a commonly used pesticide in the coffee production chain. Although it has only been detected in roasted coffee, it is unlikely that OPP can be formed during roasting. Its acidic nature may lead to the formation of conjugates with natural matrix components. The objective of this study is to optimize an analytical method to discover how these conjugates may mask the presence of OPP in coffee. Sample extraction with hexane followed by basic hydrolysis and then a QuEChERS method allows the presence of OPP to be quantitatively detected via UPLC-MS/MS. The optimized method was applied to the same Arabica coffee (Brazil), and the quantification of comparable amounts of OPP was observed in both green and roasted samples (34.8 vs 32.2 µg/kg). The optimized procedure detected twice the amount of OPP in roasted samples, compared to the QuEChERS method, suggesting that roasting causes the partial hydrolysis of OPP conjugates.

Phthalimide Residue in Coffee: Does It Solely Derive from Folpet?

Folpet, a fungicide used on several crops, easily degrades into phthalimide (PAI) at high temperatures and basic pH. The maximum admitted limit for Folpet in foodstuffs as coffee is defined by the sum of its amount and that of PAI. Noteworthy, PAI can also arise from the reaction between ubiquitous phthalate derivatives and NH3. This work aims to demonstrate that the detection of PAI in roasted coffee is not necessarily diagnostic for Folpet as it can also originate from the reaction between phthalic anhydride (PAA), derived from phthalates, and amino acids (AAs), as a NH3 source. Thermal treatment of AAs with PAA confirmed that PAI generation follows a temperature-dependent path. Experiments with diethyl phthalate (DEP) and AAs have shown that maximum PAI generation via heating occurs at 200 °C for 60 min. PAI generation has also been proven for Folpet-free green coffee beans that were heated under laboratory and industrial roasting conditions.

Old Yellow Enzyme homologues in Mucor circinelloides: expression profile and biotransformation.

The reduction of C=C double bond, a key reaction in organic synthesis, is mostly achieved by traditional chemical methods. Therefore, the search for enzymes capable of performing this reaction is rapidly increasing. Old Yellow Enzymes (OYEs) are flavin-dependent oxidoreductases, initially isolated from Saccharomyces pastorianus. In this study, the presence and activation of putative OYE enzymes was investigated in the filamentous fungus Mucor circinelloides, which was previously found to mediate C=C reduction. Following an in silico approach, using S. pastorianus OYE1 amminoacidic sequence as template, ten putative genes were identified in the genome of M. circinelloides. A phylogenetic analysis revealed a high homology of McOYE1-9 with OYE1-like proteins while McOYE10 showed similarity with thermophilic-like OYEs. The activation of mcoyes was evaluated during the transformation of three different model substrates. Cyclohexenone, α-methylcinnamaldehyde and methyl cinnamate were completely reduced in few hours and the induction of gene expression, assessed by qRT-PCR, was generally fast, suggesting a substrate-dependent activation. Eight genes were activated in the tested conditions suggesting that they may encode for active OYEs. Their expression over time correlated with C=C double bond reduction.