Reduction of the polycyclic aromatic hydrocarbon levels in dried red peppers (Capsicum annuum L.) using heat pump-assisted drying

Highlights

• To reduce polycyclic aromatic hydrocarbons, PAHs determination in dried peppers is important.

• Using heat pump-assisted drying, the PAHs content of dried red pepper is reduced.

• PAHs content reached minimal after 18 and 4 h of hot and cooler air drying, respectively.

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are primarily produced during the incomplete combustion of organic matter. PAHs are suspected endocrine disruptors and possible carcinogenic materials. The major sources of human exposure to PAHs are inhaled fumes and food. The aim of this study was to provide an alternative drying method to mitigate PAH formation in dried red peppers. We prepared dried red pepper samples using air-drying and heat pump-assisted drying methods, and measured the concentrations of four PAHs (PAH4), benzo[a] anthracene (B[a]A), chrysene (CHR), benzo[b]fluoranthene (B[b]F), and benzo[a]pyrene (B[a]P), in the resulting pepper samples. The PAH concentrations ranged from 3.61 to 18.0 µg/kg and from 2.22 to 8.35 µg/kg in the air-dried and heat pump-dried pepper samples, respectively. Overall, the results have shown that dried peppers contain PAH4, that the drying conditions for these contaminants should be optimized for mitigating the PAH formation in dried red peppers.

Introduction

The fruits of Capsicum are used as vegetables, natural flavorings, and coloring agents (Luning, Yuksel, Vries, & Roozen, 1995). Ground red pepper (Capsicum annuum L.), in particular, is used as a natural flavoring and coloring agent for pastes, pickles and sauces (Isidoro, Cotter, Fernandez, & Southward, 1995). Approximately 1,990,000 ha of land worldwide is used to cultivate red peppers, generating an annual production of approximately 2,480,000 tons (Judy. , 2017). In the Republic of Korea, red peppers were cultivated on 32,179 ha of land to yield 85,453 tons of peppers in 2016 (Statistics Korea, 2016). This plant is an essential component of traditional Korean foods because of its unique pungency, sweet taste, and color. Kimchi, which became the first Korean food to earn a Codex standard (CAC, 2001), contains 20.1% red pepper powder, which represents the second most-abundant ingredient after oriental cabbage (Kim, Park, & Hwang, 2004).

Most harvested fresh red peppers are processed into powder, and the annual consumption of red pepper powder in the Republic of Korea is approximately 2.5 kg per capita (Park, 1999). Korean producers and importers must respect the regulations relating to red pepper processing to ensure the safety and quality of their product. Red peppers have traditionally been dried by spreading them on the ground in a single layer using nets and exposing them to sunlight and open air for 3–6 d. However, sun-drying is a slow process and depends on weather conditions. Moreover, sun-drying can result in insufficiently dried red peppers, which are susceptible to fungal contamination and subsequent mycotoxin production (Kabak & Dobson, 2017). Alternatively, since 1980, some Korean farms have used bulk-type dryers based on the conventional air-drying method to dry red peppers using electric heating (Hallas, Hahn, & Korndorfer, 1988). During air-drying, de-stemmed red peppers are usually dried at 50–60 °C for 48 h, depending on the moisture content of the sample (Cheongyang-gun Agricultural Technology Center in Cheongyang-gun, Chungcheongnamdo, Republic of Korea). However, under adverse temperature and humidity conditions, air-drying can be performed at higher temperatures to compensate for the extended drying time.

On the other hand, food processes such as drying, grilling, and smoking can produce polycyclic aromatic hydrocarbons (PAHs) (Singh, Varshney, & Agarwal, 2016). Therefore, the possible formation of heat-induced PAHs is a concern associated with these methods. The amount of PAHs formed in foods has been reported to vary based on the drying method used. The total PAH concentration, including benzo(a)anthracene (B(a)A), chrysene (CHR), benzo(b)fluoranthene (B(b)F), and benzo(a)pyrene (B(a)P), as well as other PAHs, in fresh fish samples was reported to be 11.0 ± 0.1 µg/g, while the total PAH levels were 35.7 ± 0.2 µg/g for sun-dried, 47.7 ± 0.2 µg/g for oven-dried, 79.5 ± 0.2 µg/g for charcoal-dried, and 188.1 ± 0.2 µg/g for firewood-dried fish samples (Okenyi, Ubani, Oje, & Onwurah, 2016). The European Food Safety Authority (EFSA) has suggested that the PAH4, which include B(a)A, CHR, B(b)F, and B(a)P, are among the 15 top-priority PAHs that are the most suitable indicators of PAHs in foods (European Commission, 2006, European Commission, 2011). Although literature on the PAH content in dried red peppers is very limited, Ishizaki, Saito, Hanioka, Narimatsu, and Kataoka (2010) reported that dried red peppers presented a PAH4 content of 35.5 ng/g and compared this value to those of other food samples: blended coffee, 1.80 ng/g; dried shiitake, 30.9 ng/g; dried radish strips, 4.00 ng/g; dried konbu, 1.70 ng/g; dried hijiki, 11.1 ng/g; burnt rice, 11.0 ng/g; burnt bread, 1.90 ng/g. Additionally, starting from April 1, 2016, dried culinary herbs and spices (DCHS) entering the EU market must not exceed a maximum level (ML) of 10 μg/kg for B(a)P and 50 μg/kg for PAH4 (Schaarschmidt, 2016).

However, although the study of Ishizaki et al. (2010) implied that drying red peppers contributed to the formation of PAHs, the details of the drying methods involved were not given. The purpose of our study was to develop a well-controlled drying method for red peppers that could mitigate the formation of PAHs during processing using heat pump-assisted drying.