Development of a database of capsaicinoid contents in foods commonly consumed in Korea

Abstract Chili peppers (Capsicum annuum L.) are widely consumed worldwide, and the health benefits of capsaicinoids (the active compounds in chili peppers) have been suggested. However, the link between capsaicinoid consumption and the risk of certain cancers remains controversial. Capsaicinoid consumption level is an important determinant of its potential health effects. This study sought to construct a database of capsaicinoid contents in foods commonly consumed in Korea (CAPKO) to enable a more reliable estimation of capsaicinoid intake. Capsaicinoid‐containing foods were identified from the Korea National Health and Nutrition Examination Survey datasets and divided into eight categories: chili peppers, red pepper powder, hot sauce, kimchi, salted seafood, red pepper paste, instant noodles, and convenience foods other than instant noodles. The capsaicinoid contents of primary capsaicinoid sources (chili peppers, red pepper powder, and hot sauce) were estimated from the literature. For the remaining food categories, the contents of primary capsaicinoid sources were identified from standardized recipes (kimchi) or food labels (salted seafood, red pepper paste, and convenience foods other than instant noodles). Then, capsaicinoid contents were estimated by calculation using the identified capsaicinoid source contents and the estimated capsaicinoid content in these sources. This information was unavailable for instant noodles, and capsaicinoid content was measured by HPLC analyses. This study developed the CAPKO database, which includes a variety of foods with varying levels of spiciness, which can be used in combination with dietary surveys to estimate capsaicinoid intakes. Therefore, this study established a framework for future database development for other compounds with potential health effects.


| INTRODUC TI ON
Chili peppers (Capsicum annuum L.) are among the world's most widely used spices and are particularly popular in Asia, Latin America, and Africa. Moreover, spicy foods are the mainstay of many cuisines across the globe. C. annuum varieties encompass a wide range of chili pepper shapes and sizes, both mild and hot (Wang, Xia, Wang, Luo, & Huang, 2009).
The pungency or spiciness of chili peppers is directly correlated with the concentration of capsaicinoids present in the fruit. The most commonly occurring capsaicinoids are capsaicin (8-methyl-N-vanillyl-6-nonenamide) and dihydrocapsaicin (8-methyl-N-vanillylnonanamide), which together constitute approximately 90% of all capsaicinoids (Barbero, Liazid, Azaroual, Palma, & Barroso, 2016). Capsaicin is an irritant that produces both thermal and burning sensations upon contact with oral or skin mucosa (Caterina et al., 1997). Capsaicin-induced irritation is mediated by transient receptor potential vanilloid I (TRPV1) or vanilloid receptor 1 (Julius, 2013). TRPV1 is a nonselective cation channel that is also activated by heat (>42°C), protons, and physical abrasion (Caterina et al., 1997). The activation of TRPV1 allows the preferential influx of Ca 2+ cation, resulting in the depolarization of neurons and the propagation of nociceptive signals to the brain and spinal cord (Caterina et al., 1997;Cui et al., 2006).
The topical application of capsaicin has been extensively studied as an effective pain management alternative (Fattori, Hohmann, Rossaneis, Pinho-Ribeiro, & Verri, 2016). When TRPV1expressing sensory nerve fibers are exposed to high or repeated capsaicin doses, the TRPV1 receptors undergo a refractory state (desensitization) that inhibits the receptor function (Comunanza, Carbone, Marcantoni, Sher, & Ursu, 2011). Capsaicin-induced desensitization causes the sensory neurons to become less responsive to endogenous TRPV1 agonists, resulting in analgesia (Anand & Bley, 2011). TRPV1 occurs not only in nociceptive sensory neurons but also in vascular endothelial cells, hepatocytes, adipocytes, smooth muscle cells, fibroblasts, T cells, mast cells, and astrocytes (Gunthorpe & Szallasi, 2008). This widespread expression of TRPV1 in vivo suggests its potential role in these cells as a modulator of intracellular calcium levels (McCarty, DiNicolantonio, & O'Keefe, 2015). In fact, capsaicin has been linked to many health benefits including protection from cardiovascular disease, insulin sensitivity improvement, and weight gain amelioration mainly through TRPV1 activation (Baskaran et al., 2017;Ma et al., 2011;Marshall et al., 2013;McCarty et al., 2015). Additionally, anticancer activity of capsaicin has been shown in various types of cancer, including lung, prostate, and breast cancer, partly due to its ability to induce cell-cycle arrest or apoptosis (Clark & Lee, 2016).
Nonetheless, capsaicin has also been suggested to possess co-carcinogenic effects in skin cancer (Bode & Dong, 2011). Exposure to capsaicin promoted the growth of skin tumors initiated by 7,12-dimethyl benz(a)anthracene or 12-O-tetradecanoylphorbol-13-acetate in mice, although capsaicin alone did not develop skin cancer (Liu et al., 2015). Moreover, some epidemiological studies have suggested an association between high chili pepper consumption and an increased cancer risk, especially gastric cancer (Chen et al., 2017;Lopez-Carrillo, Hernandez Avila, & Dubrow, 1994). However, the evidence for increased risk of cancer by capsaicinoid consumption is insufficient. No clear genotoxicity has been associated with capsaicinoid exposure, and potential confounding factors (e.g., food contaminants) in previous epidemiological studies have been pointed out (Bley, Boorman, Mohammad, McKenzie, & Babbar, 2012). A meta-analysis study reported that moderate capsaicin consumption was associated with protection from gastric cancer development, whereas medium or high consumption increased the risk of this disease (Pabalan, Jarjanazi, & Ozcelik, 2014). Therefore, a clear link between capsaicin or capsaicinoids and cancer risk remains to be established.
Given that the amount of capsaicinoid consumption might determine its potential health effects, a means to accurately estimate capsaicinoid consumption would be a useful risk assessment tool.
Previous capsaicinoid consumption estimation has mainly relied on characterizing the frequency of chili pepper or chili pepper-containing food consumption without accounting for capsaicinoid content (Chen et al., 2017;Lopez-Carrillo et al., 1994). The lack of a comprehensive database of the capsaicinoid contents of different food items makes it difficult to determine the association between capsaicinoid consumption and health effects.
The demand for spicy foods in Korea has accelerated the development of various spicy products, such as hot-flavored instant noodles. Various cultivars of "gochu" (chili pepper) are available in Korea, all of which vary in spiciness intensity (Kim, Park, & Hwang, 2002).
Red pepper powder ("gochugaru") is a Korean chili-based product that is sold as powder or flakes and is commonly used in Korean cuisine. This product is a major condiment in spicy food and a primary source of capsaicinoids in the Korean diet. Its spiciness largely depends on its pepper cultivar composition  and cultivation location . Capsaicinoid consumption may be reasonably high for certain individuals who consume spicier versions of the same foods by adding more ingredients that contain capsaicinoids (e.g., red pepper powder) or using ingredients that contain high levels of capsaicinoids (e.g., red pepper powder with higher capsaicinoid content). These variations highlight the importance of developing a database of capsaicinoid content in commonly consumed food items in Korea to allow for a reliable estimation of capsaicinoid intakes and the identification of individuals with high capsaicinoid consumption.
Therefore, the CAPKO database was created in this study to estimate the capsaicinoid content of foods commonly consumed in Korea. The information provided by this database will allow for the evaluation of capsaicinoid intakes in Korea and the identification of subpopulations that consume high amounts of capsaicinoids to determine associated health effects. Moreover, this study establishes a methodological framework for the development of databases for other compounds with potential health effects.

| Selection of capsaicinoid-containing food items
Capsaicinoids in the Korean diet are primarily derived from chili peppers, red pepper powder, and hot sauce. Therefore, food items that contained these components were identified using the Korea National Health and Nutrition Examination Survey (KNHANES) datasets. The KNHANES is a nationwide survey program conducted by the Korea Centers for Disease Control and Prevention to assess the health and nutritional status of the Korean population. This representative, nationwide, and cross-sectional survey annually gathers information from approximately 10,000 individuals aged ≥1 year (Kweon et al., 2014). The nutritional component of the KNHANES assesses dietary behaviors, food frequency, and food intake (Kweon et al., 2014), and therefore serves as a useful resource to estimate dietary exposure (Kwon, 2014 Figure 1 illustrates a flow chart of the steps taken to develop the CAPKO database. To estimate the capsaicinoid content of selected food items, the capsaicinoid levels of primary capsaicinoid sources (chili peppers, red pepper powder, and hot sauce) were first compiled from the literature. For the remaining food categories, their major capsaicinoid sources were determined, and capsaicinoid contents were identified from standard recipes or food labels. Afterward, the capsaicinoid contents of kimchi, salted seafood, red pepper paste, and convenience foods other than instant noodles were estimated via calculation. Capsaicinoid levels in kimchi and red pepper paste were also available from the literature, and these values were compared with the estimated values to validate calculations in this study. When the content of the primary capsaicinoid source was unidentifiable (e.g., instant noodles), capsaicinoid levels were analyzed via high-performance liquid chromatography (HPLC) analyses.

| Estimation of capsaicinoid content through literature searches
The capsaicinoid contents of chili peppers, red pepper powder, and hot sauce were estimated by literature searches. Chili peppers are often consumed fresh, and four types are mainly produced for fresh consumption. Red pepper powder is obtained by processing red chili peppers. However, the chili pepper cultivars for red pepper powder are different from those produced for fresh consumption. Hot sauces can be made from various kinds of peppers such as Tabasco pepper (Capsicum frutescens), cayenne pepper (Capsicum annuum), and habanero pepper (Capsicum chinense), as well as mixtures of these varieties. Therefore, the capsaicinoid contents of chili peppers, red pepper powder, and hot sauce can vary considerably.
Capsaicinoid contents in chili peppers, red pepper powder, and hot sauce were obtained from previous reports that analyzed capsaicinoids using reliable analytical methods such as HPLC and gas chromatography (GC). Capsaicinoid content (combined capsaicin and dihydrocapsaicin levels) was expressed as milligrams of F I G U R E 1 Flow chart of the steps taken to develop the database of capsaicinoid contents in foods commonly consumed in Korea capsaicinoid in 100 g of wet weight or dry weight, depending on the way they are consumed; wet weight was used for Korean chili pepper as well as hot sauce, whereas dry weight was used for red pepper powder.
When capsaicin or dihydrocapsaicin content was only available on a dry weight basis in chili peppers, the values were converted to a wet weight basis after correcting for water contents in fresh and dried peppers using data available from the Korean Food Composition Table (KFCT, version nine) (RDA, 2017). The KFCT is a database of energy and nutrient contents in foods commonly consumed in Korea. The moisture correction factor was calculated using the following formula: (100 -fresh pepper water content)/ (100dried pepper water content). When dihydrocapsaicin levels were not measured, the ratio of capsaicin to dihydrocapsaicin for a given cultivar (Korean chili pepper or Chengyang chili pepper) derived from other studies that analyzed both capsaicinoids was used to estimate dihydrocapsaicin level.
Red pepper powder is a major source of capsaicinoids in many foods, and therefore contributes significantly to capsaicinoid intake. Additionally, capsaicinoid content in red pepper powder can be affected by many factors including region, cultivar, and drying conditions (Kim et al., 2002;Lee et al., 2013;Wang et al., 2009), resulting in variation in red pepper powder spiciness (Yu, Choi, & Lee, 2009). In this study, literature covering the capsaicinoid content of red pepper powders produced in Korea was comprehensively searched. A total of six studies used GC or HPLC to analyze the capsaicinoid levels of various red pepper powders consumed in Korea. One study provided only a mean capsaicinoid content (35.3 mg/100 g of red pepper powder) for a variety of red pepper powders that were purchased from different locations in Korea (Dang et al., 2018). Individual values from five other studies were used for estimations in this study. Capsaicinoid levels in red pepper powder were estimated in terms of five levels of spiciness.
These red pepper powder capsaicinoid concentrations were used throughout this study to estimate the capsaicinoid content in kimchi and other foods that contain red pepper powder as their primary capsaicinoid source.

| Estimation of capsaicinoid content via calculation
Red pepper powder is a major capsaicinoid source in kimchi, salted seafood, red pepper paste, and many other processed foods. In addition to red pepper powder, convenience foods other than instant noodles contain hot sauce as a major source of capsaicinoids. For each food category, this study examined whether the amount of these capsaicinoid sources can be identified using standard recipes or food labels that provided information on their major ingredients and their content, as mandated by Korean law.
For example, standardized recipes for different types of kimchi were searched. The weights of the main ingredients were combined, and red pepper powder portion (%) was calculated. When standardized recipes only provided the fresh weight (rather than drained weight) of cabbage or radishes, they were corrected for weight loss (approximately 10%) due to moisture loss during the salting and draining processes (Han & Seok, 1998). Capsaicinoid content was further corrected to reflect the degradation by microorganisms during fermentation (Ku, Park, & Park, 2004). For kimchi types for which standardized recipes were unavailable, their red pepper powder content was estimated from the red pepper powder content of other kimchi made from vegetables with similar mechanical properties.
For the estimation of capsaicinoid source contents (%) in salted seafood, red pepper paste, and convenience foods other than instant noodles (e.g., kimchi dumpling and spicy canned tuna), products available in the market were examined, and the food labels were reviewed to identify red pepper powder and hot sauce contents. Red pepper powder contents were averaged from different products within the same food item classification.
Afterword, capsaicinoid content was calculated using the identified capsaicinoid sources contents (red pepper powder and/or hot sauce) based on standard recipes and food labels coupled with the capsaicinoid content reported in the literature. The estimated capsaicinoid levels in capsaicinoid sources were multiplied by the capsaicinoid source contents and divided by 100. When foods contained more than one capsaicinoid source (e.g., spicy canned tuna), the capsaicinoid levels derived from each capsaicinoid source were combined to estimate capsaicinoid contents. Capsaicinoid content was expressed as milligrams of capsaicinoids per 100 g of consumable food.

| Measurement of capsaicinoid content via HPLC analysis
Capsaicinoids in instant noodles are contained exclusively in the seasoning powders or liquids provided with each noodle block. Major sources of capsaicinoids in seasonings include red pepper powder and chili oleoresin. Hot flavors can originate from different combinations of chili peppers; however, this information is often proprietary.
Therefore, the capsaicinoid level in instant noodles was determined via HPLC analysis of the seasonings provided with the noodle block.
Capsaicinoid levels were expressed as milligrams of capsaicinoids per 100 g of seasoning. Seasoning size (weight) varied among the examined products, and therefore, the capsaicinoid content was also expressed per seasoning packet (one serving).
A total of 24 instant noodle products were selected upon considering their spiciness, market share, and inclusion in the KNHANES.
The samples included 16 regular (packaged in a bag) and 8 cup noodles produced by four major manufacturers (Nongshim, NS; Ottogi, OTG; Paldo, PD; and Samyang, SY). All items were purchased from local markets in Seoul, Korea. Analytical standards of capsaicin (≥98.5%) and dihydrocapsaicin (≥97.0%) were purchased from Sigma-Aldrich. Stock solutions of capsaicin and dihydrocapsaicin prepared in methanol were stored in the dark at −20°C and further diluted to the desired concentration with 75% methanol to provide a daily working standard. All other reagents and solvents used were of analytical or HPLC grade.
Capsaicinoids were extracted from seasoning powders or liquids via the heating-block method, as described in a previous study with minor modifications (Namgung, Lee, & Ha, 2013). Briefly, the samples (powder, 3 g; liquid, 1 g) were heated in 75% (powder) or 100% (liquid) methanol at 95°C for 1 hr. The extraction was performed three times for each sample. The extracts were collected and centrifuged at 6,200 g for 10 min to remove particulates. Supernatants were adjusted to 25 ml with methanol and filtrated into an HPLC sample vial through a 0.2-μm syringe filter.
HPLC analyses were carried out on a Gilson HPLC system equipped with an auto-injector and a UV/VIS detector set at 280 nm (Gilson, Inc.). The capsaicinoids were separated with a Zorbax 300SB-C18 (4.6 × 250 mm, 5 μm) column (Agilent Technologies, Inc.) by elution with isocratic acetonitrile/water containing 0.1% acetic acid 40/60 (v/v) with a 1 ml/min flow rate. The injection volume was 20 μl.
The capsaicin standard was dissolved in 75% methanol at concentrations of 0.313, 1.25, 5, 20, and 80 μg/ml. Dihydrocapsaicin was dissolved in 75% methanol at concentrations of 0.625, 2.5, 10, and 40 μg/ml. The standard solutions were analyzed under the same analytical conditions as the samples, and the obtained standard curve plots (peak area against concentration) were used to quantify the capsaicin or dihydrocapsaicin level in instant noodle seasonings.

| Chili peppers
Four main types of chili peppers ("gochu") are cultivated for fresh consumption in Korea (Park et al., 2019). The most common cultivar is Korean chili pepper ("Nokguang gochu") or Korean hot pepper, also known as Korean dark green pepper or Korean red pepper depending on its color/ripening stages (the peppers are dark green when unripe).
Cheongyang chili pepper ("Cheongyang gochu") is the hottest cultivar (Hwang et al., 2011). Shishito pepper ("Kkawri gochu") is a mildly hot East Asian variety that is also known as ground cherry pepper in Korea due to its wrinkled surface (Park et al., 2019). Cucumber chili peppers ("Oi gochu") have a crunchy texture and are not spicy (Park et al., 2019).
Capsaicinoid contents varied among the examined cultivars (Table 1). Korean chili pepper (green) was found to contain 4.86 mg capsaicinoid/100 g fresh pepper, which increased to 9.71 mg in the ripe (red) peppers (Table 1). With approximately five times more capsaicinoids than Korean chili peppers (Table 1)  The moisture correction factor was calculated using the following formula: (100 -fresh pepper water content)/ (100 -dried pepper water content).
b Dihydrocapsaicin levels were estimated using the same ratio of capsaicin to dihydrocapsaicin for a given cultivar derived from other studies that analyzed both levels. c The value represents an average of capsaicinoid levels measured from peppers cultivated in 13 different regions.

| Red pepper powder
Many cultivars of chili peppers are produced in Korea. Most chili peppers are cultivated for the production of red pepper powder, which is obtained after a drying process (Kim et al., 2002).  (Dang et al., 2018). Individual values of a total of 94 capsaicinoid contents (mg/100 g) were obtained from five additional studies (Choi, Jeon, & Park, 2000;Ham et al., 2012;Kim et al., 2002;Ku, Lee, & Park, 2012;Yu et al., 2009), which are listed in Table S1 and are shown in increasing order in Figure 2.
The first (<10 mg/100 g) and last (>220 mg/100 g) three values were excluded due to their exceptionally low or high levels.   (Table S1). These results may have been due to a sample size limitation rather than analytical bias.

| Hot sauce
KNHANES-surveyed hot sauces included sweet hot chili sauce, Tabasco hot sauce, and chicken seasoning sauce. The capsaicinoid content in sweet hot chili sauce was estimated to be 1.6 mg/100 g sauce, averaged from the capsaicinoid contents of two products (Ham et al., 2012). For the Tabasco sauce, only one product is predominant in the Korean market, and it was reported to contain 20 mg capsaicinoid/100 g sauce (Betts, 1999). No reports were available for chicken seasoning sauce, and therefore, sweet hot chili sauce values were used instead due to their similar spiciness (Table 2).

| Kimchi
In Korea, kimchi is a popular side dish of salted and fermented vegetables. Kimchi types primarily vary by the main vegetables used for their preparation, and these include napa cabbage, Korean radish, young radish, cucumber, green onion, and many other vegetables. With the exception of white kimchi, kimchi is typically prepared with varying quantities of red pepper powder with varying degrees of spiciness. Some types of kimchi include water in their preparations, and these are properly referred to as "watery kimchi" (Kong et al., 2005). Watery kimchi contains less red pepper powder than typical kimchi (without added water) (Kong et al., 2005). A total of 11 types of kimchi were retrieved from the KNHANES 24-hr recall datasets. These included napa cabbage kimchi, cubed Korean radish kimchi, young radish kimchi, watery kimchi, ponytail radish kimchi, mustard green kimchi, cucumber kimchi, green onion kimchi, rapeseed leaf kimchi, and sonchus-leaf crepidiastrum kimchi.
Standardized recipes for different types of kimchi were searched, and standardized recipes for napa cabbage kimchi were found to be available (Cho, Park, & Rhee, 1997;Choi, Hwang, & Jo, 1997), in addition to cubed Korean radish kimchi (Choi et al., 1997), young radish kimchi (Kong et al., 2005), and watery kimchi (Kong et al., 2005), which are more commonly consumed than other types of kimchi. For these studies, red pepper powder proportions were calculated based on the main ingredient total weights (Table 3). Kimchi preparation typically includes salting and draining of the main vegetable ingredients (cabbage or radish). When standardized recipes only provided fresh cabbage or radish weights, these were corrected for weight loss (approximately 10%) due to moisture loss during the salting and draining processes (Han & Seok, 1998). Additionally, capsaicinoid content is reportedly to be decreased by microorganisms-mediated degradation (Lee et al., 2015). For instance, capsaicinoid content decreased by approximately 20% (10%-25%) in napa cabbage kimchi during fermentation (Ku et al., 2004). Considering that red pepper powder is a major source of capsaicinoids in kimchi, the red pepper content was further corrected to reflect the level of capsaicinoid degradation during fermentation (Table 3).
Standardized recipes were unavailable for other types of kimchi, and therefore, their red pepper powder content was estimated from that of other kimchi made from vegetables with similar mechanical properties. For example, the red pepper powder content of cubed Korean radish kimchi was used to estimate that of cucumber kimchi, and that of young radish kimchi was used to estimate red pepper powder content in the remaining types of kimchi (ponytail radish kimchi, mustard green kimchi, green onion kimchi, rapeseed leaf kimchi, and sonchus-leaf crepidiastrum kimchi) ( termine whether estimations in this study fell within these ranges, the capsaicinoid content was estimated in kimchi using five levels of capsaicinoids in red pepper powder ( Figure 2) and identified red pepper powder contents in kimchi products (  (Ku et al., 2004), which was also comparable to the levels of capsaicinoids estimated in this study. For comparison, another study reported 0.33 mg capsaicinoids/100 g napa cabbage kimchi, which was averaged from 121 samples (Dang et al., 2018). However, it is worth noting that the kimchi was first rinsed to remove the red pepper powder in that study, which could have led to an underestimation of its capsaicinoid content.

| Salted seafood
Salted seafood ("jeotgal") or fish sauce (liquid "jeot") is salted and fermented dish made from seafood, such as shrimp, oyster, clam, squid, fish, or fish roe. Unlike other salted seafood products (e.g., salted shrimp and salted anchovy), some salted seafood products are seasoned with red pepper powder (e.g., salted oysters and salted squid). Among the various salted seafood items that contain red pepper powder, a total of seven were found to be consumed by Koreans, according to the 2012-2016 KNHANES. These included salted oysters, pollock roe, squid, baby squid, octopus, fish gills, and fish guts.
Presently, salted seafood is more often purchased than prepared at home. The capsaicinoid content from this food category was estimated using the red pepper powder content listed on the food label provided by each product's respective manufacturers (  (Table 5). Therefore, a 5% red pepper powder content was assumed to estimate the capsaicinoid content in the aforementioned food items, except the salted pollock roe. This 5% criterion was also used for the two remaining salted seafood items for which red pepper powder content information was unavailable (salted baby squid and salted fish gills) due to their similar preparation (  (Table 5).

| Red pepper paste
Red pepper paste ("gochujang") is a fermented condiment made from red pepper powder, glutinous rice, fermented soybean, barley malt powder, and salt. Although traditional red pepper paste is naturally fermented at home for several years, modern red pepper paste is produced commercially, and most Koreans purchase it at grocery stores or markets. Red pepper paste is extensively used in Korean cuisine and is also often mixed with other condiments such as vinegar or soy bean paste.
The red pepper powder content in commonly consumed products ranged between 9.3% and 12.5%, with 11.3% being the most typical proportion. Therefore, the red pepper powder content in red pepper paste was estimated at 11.3%. Additionally, changes in capsaicinoid content during fermentation were also accounted for. Similar to kimchi (Section 3.4), the capsaicinoid content of red pepper paste has been shown to decrease after preparation (Lee et al., 2015). This decrease in capsaicinoid amount continued throughout the 90-day fermentation period, which typically results in a capsaicinoid loss of approximately 10% (Yang, Lee, & Choi, 2018). Therefore, the estimated red pepper powder content was reduced from 11.3% to TA B L E 3 Estimation of red pepper powder content in various kimchi products Red pepper powder content was corrected for capsaicinoid loss during fermentation (approximately 20%).
c Weight was corrected for water loss (10%) during salting and draining.
d Estimation was also used for cucumber kimchi.
e Estimation was also used for ponytail radish kimchi, mustard green kimchi, green onion kimchi, rapeseed leaf kimchi, and sonchus-leaf crepidiastrum kimchi.
10.2% to reflect the decrease in capsaicinoids during fermentation (Table 6). When the five levels of capsaicinoid content in red pepper powder ( Figure 2) were considered, the red pepper paste was estimated to contain either 2.71, 4.66, 6.00, 8.81, or 15.64 mg capsaicinoid/100 g if it was prepared with mild, slightly hot, medium hot, very hot, or extremely hot red pepper powder, respectively. This capsaicinoid content estimation in red pepper paste was comparable to the level of capsaicinoids measured in commercially available red pepper paste products. One study reported an average capsaicinoid content of 6.66 mg for 120 products commonly consumed in Korea (Dang et al., 2018) and another study reported a 3.92-5.90 mg capsaicinoids/100 g range in eight commercially available red pepper paste samples (Ham et al., 2012).
The KNHANES separated gather information on the consumption of traditional and commercial red pepper paste. According to the KNHANES datasets, both types were found to be consumed. TA B L E 4 Estimation of capsaicinoid content in various kimchi products based on the red pepper content in kimchi products (Table 3) and five levels of capsaicinoid contents in red pepper powder (Figure 2) TA B L E 5 Estimation of red pepper powder and capsaicinoid content in salted seafood   c Capsaicinoid contents were estimated based on the red pepper powder content in red pepper paste and the capsaicinoid content of red pepper powder at five levels ( Figure 2). The capsaicinoid content in the traditional red pepper paste was 2.46-9.64 mg capsaicinoid/100 g red pepper paste among 12 samples, which was similar to that of commercial red pepper paste (Jo et al., 2013). The capsaicinoid content in red pepper paste in this study was thus assumed to be the same for both traditional and commercial products. This study also estimated the red pepper powder content and capsaicinoid content of red pepper paste containing vinegar and soybean paste by adjusting the red pepper paste proportions down to 80% and 25% in red pepper paste products with vinegar and soybean paste, respectively (Table 6).

| Instant noodles
Instant noodles ("ramyeon") are a popular food in Korea, particularly among young people Yu, Jung, & Yoon, 2013). In this study, the capsaicinoid content of 24 seasonings (16 from regular noodles and 8 from cup noodles) was quantified using HPLC (Table 7). Seasoning size (weight) varied among the products, and therefore, the capsaicinoid content in a seasoning packet (one serving) was used to compare capsaicinoid contents in different instant noodles. The capsaicinoid contents in regular instant noodles could be categorized into three different flavor intensities: mild (n = 6; mean: 0.70 mg/serving), hot (n = 7; mean: 1.51 mg/serving), and extremely hot (n = 3; mean: 5.60 mg/serving). Cup noodles tended to contain comparable or slightly higher capsaicinoid concentrations compared with the same noodles packaged in a bag (

| Convenience foods other than instant noodles
Convenience foods other than instant noodles were also retrieved from the KNHANES dataset. These items included dumplings (kim- chili sauce (Table 9). The product with the higher red pepper content (OTG) had less chili sauce than the other products (  (Table 2) and five levels of capsaicinoids in red pepper powder (Figure 2).
However, heating temperatures between 100 and 190°C for 15 min did not substantially affect capsaicinoid contents (<10% reduction) (Wang et al., 2009). This suggests that canning, which is commonly achieved by maintaining the food core temperature at 121°C for a short period (Dincer, 1998) Koreans. This comprehensive CAPKO database will allow for reliable estimations of capsaicinoid consumption in Korea to identify subpopulations or individuals who consume high capsaicinoid levels.

CO N FLI C T O F I NTE R E S T
The authors declare no conflicts of interest.

E TH I C A L S TATEM ENTS
This study did not involve any human or animal testing.   Table 3.

Youngjoo
c Capsaicinoid content was estimated based on the red pepper powder content in kimchi dumplings and the capsaicinoid content in red pepper powder at five levels ( Figure 2). a Information was obtained from the food label provided by the manufacturers.

TA B L E 9 Estimation of capsaicinoid content of spicy canned tuna
b Capsaicinoid contents were estimated by combining the capsaicinoid level derived from red pepper powder at five levels ( Figure 2) and the capsaicinoid content in chili sauce (Table 2).