Avaliação da contaminação por microplásticos e seus efeitos sobre a composição elementar de infusões de café servidos em copos de poliestireno

Abstract

The contamination of food and beverages with microplastics (MP) from environmental, packaging, and containers has been evidenced in recent years. Moreover, adsorptive processes involving MP and inorganic species in aqueous media have been reported. Nevertheless, studies on the effect of MP on the inorganic composition of food and beverages are still scarce. Thus, this work aims to determine the presence of MP and their impacts on the concentration of Ca, K, Mg, Mn, and P from coffee infusions served in polystyrene (PS) cups. Initially, the effect of temperature on MP release from PS cups was assessed by measuring the amount of MP released with water at room temperature (TRoom) and at 70 °C (T70). Subsequently, coffee infusions from five brands (A, B, C, D, and E) were prepared by pouring heated water on ground coffee in paper filters, and the resulting infusions were added individually to glass cups (control group, CG) and to PS cups (plastic group, PG) with 150 mL of coffee infusion in each cup. CG and PG samples (n = 10 each) were subjected to alkaline digestion (10% w v-1 KOH and 30% w v-1 H₂O₂) to determine MP content (MP/150 mL). For the elemental composition analysis (Ca, K, Mg, Mn, and P), filtered coffee infusions (n = 3) from both groups underwent microwave-assisted acid digestion (65% w v-1 HNO₃ and 30% w v-1 H₂O₂) followed by Inductively Coupled Plasma Optical Emission Spectrometry (ICP OES) analysis. The coffee infusions in plastic cups exhibit a mean of 12±11 MP/150 mL, namely fibers (6±9 MP/150 mL), and plastic fragments (6±5 MP/150 mL), whereas the TRoom and T70 exhibit 10±4 and 21±4 MP/150 mL respectively, wherein 5±2 and 11±3 MP/150 mL where fibers and 3±2 and 9±2 MP/150 mL plastic fragments. Four coffee brands (A, B, D, and E) from the PS group showed significant differences (p ≤ 0.05) for the concentrations of Ca. Similarly, K and Mg content in PG showed significant differences from CG in Arabica coffee samples (D and E). As for the Mn content, coffee sample D showed a significant difference. Generally, a decrease of 11.8±0.2% (Mg), 10.2±0.7% (K), 22±9% (Mn), and 25±16% (Ca) was observed for PG samples. The most significant content variation was observed for Ca, especially for sample A (ca. 49%). Therefore, the study demonstrated the release of PS MP from the cup into the coffee infusion at 70 °C, and a significant decrease (p ≤ 0,05) in Ca, K, Mg, and Mn content when the infusion passes through the plastic cup.