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ISSN : 1225-7060(Print)
ISSN : 2288-7148(Online)
Journal of The Korean Society of Food Culture Vol.35 No.4 pp.342-350
DOI : https://doi.org/10.7318/KJFC/2020.35.4.342

Questionnaire Survey of the Methods Used in Household Doenjang Production in Korea

So Young Ryu, Sang Yoo Lee, So Young Woo, Seung Yoon Kang, Jeonghun Song, A-Yeong Jeong, Hyang Sook Chun*
Advanced Food Safety Research Group, BK21 Plus, School of Food Science and Technology, Chung-Ang University
*Corresponding author: Hyang Sook Chun, Advanced Food Safety Research Group, BK21 Plus, School of Food Science and Technology, Chung-Ang University, Anseong 17546, Republic of Korea Tel: +82-31-670-3290 Fax: +82-31-670-4853 E-mail: hschun@cau.ac.kr
August 10, 2020 August 26, 2020 August 31, 2020

Abstract


This study examined the methods used in household Doenjang (Korean soybean paste) production. Nine hundred fortythree responses were obtained using a nationwide, questionnaire-based survey (2018-2019) with non-probabilistic snowballing sampling. Consistent with previous studies, the respondents were primarily over the age of 50 years (97.1%) and female (97.9%). In addition to soybeans, the most used ingredients were red pepper (85.8%) and charcoal (85.5%), which most respondents obtained through direct farming (50.4-59.9%). Seasonal production occurred later in the higher latitude regions (Gyeonggi-do, Gangwon-do, Chungcheong-do) (p < 0.01), which have lower average temperatures, and the fermentation period was shorter in the lower latitude regions (Jeolla-do, Gyeongsang-do, Jeju-do) (p < 0.01), which have higher average temperatures. There were no significant regional differences in the season when Doenjang was made, with most production occurring during January and February (81.1%). Most respondents (71.3%) made Doenjang using homemade meju (soybean block used as a starter) in a traditional way to allow the microorganisms to be naturally inoculated. These results could be used as a basis for future research on topics such as starter development, standardized production, and safety of household Doenjang.


Doenjang , meju , method , questionnaire , survey , household

초록

    I. Introduction

    Doenjang (Korean soybean paste) is a traditional Korean food made by fermenting soybeans and supplemental ingredients to create various flavors. Korea is geographically surrounded by the sea to the east, west, and south, and mountain ranges to the north, making it difficult to transport goods. Thus, long-term food storage between harvests has historically been essential to survival, leading to the development of fermented foods such as doenjang (Oh et al. 2014). Doenjang is rich in isoflavones like genistein, daidzein, glycitein-6-Oglucoside, which are well known for their anticancer effects (Ravindranath et al. 2004); doenjang made with a longer fermentation period also has stronger anticancer effects (Jung et al. 2006). Antioxidant, anti-obesity, antidiabetic, and antihypertension properties have also been reported (Kwak et al. 2007;Kwon et al. 2010;Cha et al. 2013;Kim & Kim 2014).

    In the Korean food code, doenjang is defined as a fermented food made from the incubation of bacteria, fungi, etc. on raw ingredients, primarily soybean, rice, barley, wheat or defatted soybean. Doenjang and traditional doenjang have been uniquely defined (MFDS 2018). The doenjang process is generally divided into two steps: making meju (soybean block), a fermentation starter, and then fermenting doenjang by adding soybean, brine, etc. to the meju. Depending on its production method, meju is either traditional or improved; thus, doenjang made with traditional meju is called “traditional doenjang” and doenjang made with improved meju is called “improved doenjang” (Lee et al. 2019). Traditional meju is influenced by the microorganisms present in the surrounding environment (e.g., air, straw). Therefore, it is also possible that toxin-producing fungi in the air (e.g., Aspergillus flavus, Aspergillus ochraceous) may produce mycotoxin contaminants such as aflatoxin and ochratoxin (Kim et al. 2015). To reduce toxin contamination, factories have recently begun using an improved method to artificially inoculate starter which does not produce toxins, such as Aspergillus oryzae, along with rapid fermentation and mass production, while maintaining the doenjang’s taste and functionality (Lee et al. 2016).

    Because research on doenjang production forms the basis for establishing its functionality, taste, reduction of harmful substances, etc, research on its production should include various sources (e.g., factories, households, the literature). Previous research on production methods of doenjang by Park et al. (2002) assessed doenjang making processes described in the literature (e.g., research reports, recipes, media reports) and used in factories, to establish a standardized process. This group divided doenjang into traditional and improved in their investigations of doenjang type, fermentation periods, ingredient mixing ratios, and meju ingredients. Moon & Lee (2001) studied doenjang consumption and production among housewives in Yangsan City. Using a questionnaire, they investigated intake frequency of doenjang, its production season, and the type of meju used according to age, education, and housing type. Han & Yu (2002) studied doenjang consumption and production among housewives in Seoul using a questionnaire. However, in that study, only the fermentation period of doenjang was considered, with emphasis on consumption (e.g., frequency of use, reasons for using doenjang) rather than how it is made (Han & Yu 2002).

    Most research on the methods for making doenjang was published more than 10 years ago, and insufficient research has been conducted on the conditions under which household doenjang is made. In addition, most research on homemade doenjang has been limited to a specific region, while studies assessing the entire country have not been conducted. Therefore, we sought to investigate the regional patterns of household doenjang production and describe changes since previous studies were conducted, using a nationwide, questionnairebased survey.

    II. Materials and Methods

    1. Questionnaires

    A questionnaire (IRB No. 1041078-201802-HR-022-01) was used to survey household techniques for making traditional doenjang across the country. A total of 1076 surveys were distributed, and 943 respondents’ data were collected.

    1) Sampling design

    The study was conducted during February 2018 and November 2019. The questionnaire was distributed to households in which doenjang is made in six Korean provinces: Gyeonggi provinces (GG), Gangwon provinces (GW), Chungcheong provinces (CC), Jeolla-do (JL), Gyeongsang provinces (GS), and Jeju provinces (JJ). The number of questionnaires by province was assigned considering the resident population of the six provinces (31.5% in GG, 1.9% in GW, 16.9% in CC, 16.4% in JL, 31.8% in GS, and 1.5% in JJ) which were included metropolitan cities (Seoul, Sejong, Daejeon, Gwangju, Daegu, Busan, Ulsan, etc.). (KOSTAT, 2016). Before administering a survey of this type, a list of households in which doenjang is made should be prepared. Because such a list for the entire country was practically impossible, the snowballing (non-probabilistic) sampling method was used, in which initial respondents recruit additional respondents.

    2) Questionnaire design

    According to Paek et al. (2016), most people who make homemade doenjang are aged 60 years or older. Therefore, because it was estimated that a disproportionate number of respondents would be older adults, the questionnaire was conducted by individual personal interviews, with the snowballing method. The questions were designed to be easily understood and were divided into four sections: respondent information, raw ingredients (e.g., soybeans, peppers, etc.), making meju, and making doenjang <Table 1>.

    In section one, respondent information included: age (R1), gender (R2), and area of residence (R3). In section two, raw ingredients included: supplemental ingredients (I1); salt types (I2); number of washings for soybean (I3), pepper (red pepper) (I4), charcoal (I5), and jujube (red date) (I6); purchase paths for soybean (I7), pepper (I8), charcoal (I9), and jujube (I10); storage locations for soybean (I11), pepper (I12), charcoal (I13), and jujube (I14); and storage periods for soybean (I15), pepper (I16), charcoal (I17), and jujube (I18). In section three, the methods for making meju included: type of soybean (Me1), production season (Me2), fermentation period (Me3), and fermentation location (Me4). In section four, the methods for making doenjang included: whether meju is purchased (D1), type of meju purchased (D2), whether ssi-doenjang (the very old doenjang that is added to make fresh doenjang, and maintains the doenjang as if it were passed through a certain taste) is used (D3), ssidoenjang fermentation period (D4), number of meju washings (D5), doenjang production season (D6), doenjang fermentation period (D7), and doenjang fermentation location (D8).

    2. Statistical analysis

    The survey results were analyzed using SPSS version 20. Frequency analysis was used to develop descriptive statistics and a chi-square test (χ2) was performed to identify regional differences.

    III. Results and Discussion

    1. General information

    1) Respondent information

    Respondents’ age (R1), gender (R2), and area of residence (R3) characteristics are shown in <Table 2>. Most respondents (97.1%) were over the age of 50 years, consistent with previous surveys showing that not knowing how to make doenjang is highest among those in the 20-50-year age group (Kim 2012;Peak et al. 2016). Those over age 70 years made up the largest proportion of this sample (55.5%, 503/907), followed by those in their 60s (25.9%, 235/907), 50s (15.7%, 142/907), and under 50s (2.9%, 27/907). Females made up 97.9% (890/909) of the sample and 2.1% (19/909) were male. Regional representation was 19.2% (181/943), 5.8% (55/943), 6.3% (59/943), 19.7% (186/943), 47.6% (449/943), and 1.4% (13/943) from GG, GW, CC, JL, GS, and JJ, respectively.

    2. Raw ingredients

    Among the supplemental ingredients (I1) (multiple choice), charcoal and red pepper were most common, with 85.8% (750/874) using “pepper” and 85.5% (747/874) using “charcoal”; 26.8% (234/874) endorsed using “jujube” and a relatively small number of respondents used “sesame seeds” (3.5%), “barley” (1.7%), “red pepper seeds” (1.7%), “pine needles” (1.3%), “lacquer tree” (1.0%), or “dried pollock” (0.8%) (Fig. 1). That most of these participants (over 70%) used “charcoal” or “peppers” and 7-15% used jujube or sesame seeds is like a previous study of traditional doenjang methods (Park et al. 2002). Regarding the use of salt (I2), 97.0% (853/879) used “sun salt”; “refined salt” (2%) or “bamboo salt” (1%) were rarely used.

    The number of washings of the most frequently used ingredients (I3-6) (soybean, pepper, charcoal, and jujube) was assessed. The largest proportion of respondents, 30.2% (208/688), wash soybean, the main ingredient, “4 or more than times.” Supplemental ingredients pepper, charcoal, and jujube were each commonly washed “one time,” 37.6% (258/687), 40.1% (264/659), and 42.6% (78/183), respectively.

    Regarding the purchase path of soybean, pepper, and jujube (I7, 8, and 10), “farming” accounted for the largest portion: 58.5% (411/703), 50.4% (326/647), and 59.9% (112/ 187), respectively. At a “traditional market” was also endorsed: 33.3% (234/703), 37.1% (240/647), and 27.3% (51/187), respectively. Charcoal (I9) was more often purchased at a “traditional market” (41.8%) than “directly manufactured” (29.1%). About 58% of respondents make doenjang from directly grown soybean and about 33% purchase soybean. This finding is like a previous study showing that 50% of soybean was grown directly and about 26% was purchased (Kim et al. 2003).

    Storage (I11-14) “in the storehouse” was most commonly endorsed by respondents, with 69.0% (455/659), 54.7% (346/633), 55.1% (332/603), and 46.2% (67/145) reporting this storage location for soybean, pepper, charcoal, and jujube, respectively. Soybean and charcoal, which can be stored long-term at room temperature, were also often stored on the “balcony” rather than in “refrigerated” storage (2.6% and 1.3%, respectively). Pepper and jujube, which have the potential to rot if stored long-term at room temperature, were kept on the “balcony” (20.4, 15.2%) or “refrigerated” (17.9, 22.1%), respectively.

    The storage period (I15-18) (i.e., between purchasing ingredients and making doenjang) was most commonly “more than one month” for soybeans, peppers, and jujubes: 33.2% (220/663), 33.2% (218/656), and 38.7% (65/168), respectively. Less common were “less than one week” (24.0, 25.5, 27.4%, respectively) and “immediate use” (16.1, 19.7, 15.5%, respectively). Because soybeans, peppers, and jujubes were usually obtained through “farming,” as described above, it is presumed that many respondents harvest and store these crops during “July-October” and then use them to make meju in November (i.e., more than one month later). In contrast, charcoal, (which is usually purchased in a traditional market, as described above) was “used immediately” by 36.7% (238/ 648) of respondents.

    3. Meju production

    Next, regional differences in soybean type, production season, fermentation period, and fermentation location for making meju were investigated.

    Among these respondents, 98.6% (634/643) reported using “Baektae” and 1.4% (9/643) used “Seoritae” to make meju (Me1), with no significant regional differences (χ2=5.989, p>0.05).

    The most common meju season (Me2) was “November- December” (50.7%, 325/640), while 36.3% (232/640) made meju during “September-October.” This is consistent with previous studies reporting that traditional meju was produced from November to January (Lee et al. 1997). Significant seasonal differences were observed across regions (χ2= 76.531, p<0.01). In GG, GW, and CC, which have relatively high latitudes, the reported season for making meju was usually “September-October.” In contrast, in JL and GS, which have lower latitudes, meju was typically made during “November-December.”

    The meju fermentation period (Me3) “1-3 months” was reported most frequently, by 47.9% (288/601); this is also like previous studies reporting a natural fermentation period of about one month (Lee et al. 1997;Park et al. 2002). This duration was followed by, “2-4 weeks” (15.1%), “1-2 weeks” (13.3%), and “less than one week” (12.1%). There was a significant regional difference in fermentation periods (χ2= 123.648, p<0.01). In JL and GS, fermentation for “less than one week” was more common compared with other regions. However, because there were fewer than 10 JJ respondents, the statistical reliability of the results could not be ensured.

    Meju fermentation usually took place (Me4) in the “yard (under the eaves)” (among 51.7%, 294/569), while “in the room” (28.5%, 162/569) and on a “balcony” (19.9%, 113/ 569) were less common. There was a significant regional difference in the meju fermentation location (χ2=53.651, p<0.01), although a significant pattern was not observed.

    4. Doenjang production

    Finally, doenjang making methods, including whether meju is purchased, the type of meju used, whether ssidoenjang is used, the ssi-doenjang’s degree of maturity, meju washings, doenjang season, and the fermentation period and location were explored.

    Regarding whether meju is purchased (D1), 71.3% (650/ 912) of respondents reported using “homemade” meju, while 28.7% (262/912) indicated that it is “purchased.” This is consistent with a 2001 study in which 86.8% of those surveyed use direct production and 13.2% purchase meju (Moon & Lee 2001), and with studies showing that the rate of purchasing meju is increasing (Han & Yu 2002; Peak et al. 2016). Among the types of meju (D2) used to make doenjang, 97.1% (886/912) of respondents used traditional meju and 2.9% (26/912) used improved meju. When “homemade” meju is used, all respondents prepared and used traditional meju. This replicates a previous finding: 88.9% of respondents surveyed by Moon & Lee (2001) used traditional meju. Thus, in the case of homemade meju, most households used traditional meju to make doenjang. There was a significant regional difference (χ2=12.104, p<0.05); however, because more than 25% of the items had an expected frequency 5, these data were not considered reliable.

    To initiate doenjang production (D3), only 13% (106/796) reportedly “used ssi-doenjang” (i.e., the very old doenjang that is added to make fresh doenjang, and maintains the doenjang as if it were passed through a certain taste), while most did not. There was no significant regional difference for use of ssi-doenjang. Among those who use aged ssi-doenjang (D4), 52% reported using doenjang that had aged “1-3 years,” 30% used doenjang aged “more than 3 years,” and 18% used doenjang aged “3-12 months.” There was a significant regional difference (χ2=20.930, p<0.05); however, because more than 25% of the items had an expected frequency 5, these data were not considered reliable.

    Meju washings (D5) also varied, with 35.3% (305/863) reporting washing “3 times,” followed by 29.1% (251/863) who wash “2 times.” There was significant regional variation in the number of washings (χ2=171.104, p<0.01). In GG, GW, and CC, most respondents reported that they wash “more than 4 times,” while in JL and GS, most respondents reported washing “3 times.”

    Regarding seasonality (D6), 81.1% of respondents made doenjang during “January-February,” like previous studies reporting January production (Moon & Lee 2001;Park et al. 2002). Making doenjang during “March-April” (18.9%) was the second most common. There was significant regional variance in the production season (χ2=35.448, p<0.01), though no clear pattern was observed.

    The most common fermentation durations (D7) were “3- 12 months” (36.7%, 333/908) and “1-3 months” (33.3%, 302/908). This is like the “3 month” doenjang fermentation period most frequently reported in a standardization study of doenjang production methods (Park et al. 2002). There was a significant regional difference in fermentation periods (χ2= 114.603, p<0.01). Distinctly longer compared with other regions, respondents in JL and GW reported using a period of more than one year.

    The usual fermentation sites (D8) were the “yard (under the eaves)” (65.1%, 554/851) and (26.7%, 227/851) “balcony.” There was a significant regional variation on this measure (χ2=94.880, p<0.01); however, because more than 25% of the items had an expected frequency 5, these data were not considered reliable.

    IV. Summary and Conclusion

    The methods used in household doenjang (Korean soybean paste) production were surveyed using a nationwide, questionnairebased survey with non-probabilistic snowballing sampling.

    Among 943 responses obtained, most household doenjang producers in this study were primarily over the age of 50 years (97.1%) and female (97.9%). Pepper (71.5%) and charcoal (75.7%) are the most frequently used supplemental ingredients for making doenjang. These respondents most commonly wash the soybean more than four times, whereas they typically only wash supplemental ingredients (charcoal, pepper, and jujube) once. Most supplemental ingredients (excluding charcoal) are obtained through farming (50.4- 59.9%). For meju making, soybean was usually Baektae (98%) and the production season was typically November- December (50.7%). In regions at relatively high latitudes (GG, GW, and CC), meju was made slightly later than in regions at lower latitudes (JL and GS) (χ2=76.531, p<0.01). The most common fermentation period lasted 1-3 months. In JL and GS, a fermentation period of less than one week was more common than in other regions. Fermentation usually occurs in the “yard (under the eaves)” (51.7%). These results indicate that because the mean temperature is lower, fermentation takes place slightly later at higher latitudes; likewise, fermentation periods at lower latitudes are shorter because mean temperatures are higher. Most respondents (71.3%) made doenjang using homemade meju (soybean block used as starter) in a traditional way to allow microorganisms to be naturally inoculated. However, the ssidoenjang, the very old doenjang that is added to make fresh doenjang and maintains the doenjang as if it were passed through a certain taste, was not used in 86.5% of respondents. Meju was usually washed three times in the process of making doenjang (35.3%). The doenjang season is most often January-February (81.1%), after which it is fermented for “3-12 months” (36.7%). In GW and JL, the fermentation period is significantly longer than in other regions. Most doenjang fermentation occurred in the “yard (under the eaves)” (65.1%).

    These results could be used as a basis for future research on topics such as starter development, standardized production, and safety of household doenjang.

    As a limitation of this study, since the survey targets are often elderly people, the accuracy of responses that depend on memory may be inferior, and the results of a survey conducted on Jeju were 13 cases, It is that the representativeness of the survey results may be insufficient.

    Acknowledgments

    This research was supported by grants from the National Institute of Food and Drug Safety Evaluation in 2018 (18162KFDA023) and 2020 (20162KFDA007).

    Figure

    KJFC-35-4-342_F1.gif

    Supplemental ingredients (aside from soybean) used to make doenjang.

    KJFC-35-4-342_F2.gif

    Meju and ssi-doenjang used in household doenjang production.

    (A) Whether meju is purchased, (B) Meju type, (C) Whether ssi-doenjang is used, (D) Aging duration of ssi-doenjang

    Table

    Survey questions investigating the production of household doenjang (soybean paste)

    <sup>1)</sup>Multiple choice
    <sup>2)</sup><i>Ssi-doenjang</i>: The very old doenjang that is added to make fresh <i>doenjang</i>, and maintains the <i>doenjang</i> as if it were passed through a certain taste.

    Respondent characteristics

    1)Total response of each questions was counted except for ‘no response’

    Characteristics of soybean and supplemental ingredients

    <sup>1)</sup>T.M.: Traditional market; S.M.: Super market; S.S.M.: Super-super market; O.M.: Organic market.
    <sup>2)</sup>Total response of each questions was counted except for ‘no response’

    Household meju production in six Korean provinces

    <sup>1)</sup>G, Gyeonggi-do; GW, Gangwon-do; CC, Chungcheong-do; JL, Jeolla-do; GS, Gyeongsang-do; JJ, Jeju-do
    <sup>2)</sup>**p<0.01; n.s. not significant
    <sup>3)</sup>Total response of each questions was counted except for ‘no response’

    Household doenjang production in six Korean provinces

    <sup>1)</sup>GG, Gyeonggi-do; GW, Gangwon-do; CC, Chungcheong-do; JL, Jeolla-do; GS, Gyeongsang-do; JJ, Jeju-do
    <sup>2)</sup>**p<0.01
    <sup>3)</sup>Total response of each questions was counted except for no response

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