Chongkukjang is a fermented product manufactured by short term fermentation of boiled soybean seeds using Bacillus subtilis in rice straw. It is one of the favorite traditional foods in Korea (Su et al., 2007; Kwon et al., 2011; Shin and Jeong, 2015). It contains a number of useful microorganisms and bioactive compounds that are absent from unfermented soybean products. Chongkukjang has the shortest fermentation period of 2–4 days and is fermented at a high temperature (40–43°C). The soybean proteins are degraded during fermentation process by the protein degrading enzymes of B. subtilis, and flavonoid glycosides are converted into aglycones by hydrolysis during fermentation, resulting in production of free amino acids along with related peptides (Nakajima et al., 2005; Kim N. Y. et al., 2008; Wei et al., 2015). The Koreans have been consuming Chongkukjang for hundreds of years. Significant amount of data suggests that Chongkukjang contains a number of proteins and minerals that can stimulate the generation and growth of human cells and strengthen the immune system (Choi et al., 2014; Shin and Jeong, 2015). Moreover, there are several reports on the bioactive potential of Chongkukjang such as antidiabetic, antiinflammatory, antimicrobial, antioxidant, blood pressure lowering activities, and neuroprotective effects (Kang et al., 1998; Cho et al., 2000; Yang et al., 2003; Kim et al., 2004; Kim N. Y. et al., 2008; Wei et al., 2015). Compounds like isoflavones (daidzein and genistein) are found at high concentrations in Chongkukjang and they were reported to possess the protective effect against oxidative damage related with atherosclerosis and cancer (Barnes et al., 1996; Anthony et al., 1998).

Doenjang is traditionally used in Korea as a basic seasoning (Kim et al., 2009; Nam et al., 2015). It is produced by the fermentation of cooked and crushed soybean seeds or blocks, Meju, by naturally occurring bacteria and fungi with brine in a container such as a porcelain pot and has been consumed for centuries as a source of protein and flavoring ingredient in Korea (Kim et al., 2009; Kwon et al., 2010). During recent times, the doenjang has been prepared commercially by various local firms around the Korean peninsula using a slightly modified procedure that varies in the quality as affected by the fermentation process, microbiota involved, and by the basic ingredients used, such as soybeans or a combination of soybeans and grains (Yoo et al., 2000; Park et al., 2002). Doenjang has attracted much attention due to its health-related beneficial properties such as anticancer, anti-mutagenicity, antioxidative, and fibrinolytic activity (Lim et al., 1999, 2004; Ra et al., 2004). Various types of microorganisms are involved in the fermentation of doenjang; the unique flavors and tastes are due to the decomposed products of soybean proteins from the soybean seed by the action of microorganisms during the fermentation process. A number of reports have stated that B. subtilis and B. licheniformis are the dominant microorganisms in doenjang along with Aspergillus, Mucor, and Rhizopus species (Kang et al., 2000; Nam et al., 2015). During the fermentation process, cleavage of β-glycosyl bond of isoflavone glucoside increases the content of isoflavone aglycones, including daidzein and genistein due to the rapid microbial growth (Nam et al., 2015). Daily intake of doenjang has been reported to suppress the body weight gain, cytokine levels, and serum oxidative stress in high-fat-fed mice (Nam et al., 2015). Similarly, the anti-inflammatory and anti-oxidative stress effects of doenjang have also been reported in the adipose tissue (Nam et al., 2015).

Ganjang is a kind of Korean soybean sauce made from fermented soybeans (Hong-beum, 2004). It contains approximately 15–20% salt, 50–70% water, free sugars, isoflavones, peptides, and organic acids that are produced from the soybeans during the fermentation process (Jeon et al., 2002; Shim et al., 2008). The sauce has a characteristic black color due to the presence of melanoidins, which are formed when carbonyl compounds and amino compounds combine together (Kim et al., 2011). The melanoidins present in soybean sauce are responsible for its antioxidant potential (Choi et al., 1990). Ganjang is prepared from the soybeans blocks, meju, which is dried for about 1 week and then tied with straw and dried for another 40 days. After the meju have dried, they are then fermented in a specially made clay pot mixed with salt and water. When the fermentation is complete, dark liquid separates, which is called ganjang (soy sauce or soya sauce) (Hong-beum, 2004).

Gochujang is a fermented paste made of red chili powder, glutinous rice powder, pureed soybeens and salt, seasonings like garlic and onion, sweetened with a little sugar syrup and fermented for long period in specially designed earthen vessels (Choi, 2012). It is an essential part of the Korean cuisine and is used in almost all the Korean foods like bibimbap, noodles etc. It is a basic ingredient for other sauses and pastes, it is mixed with the doenjang to make samjang, it is used to prepare the chogochujang, salad dressing etc. (Choi, 2012).

Kimchi has been in the epicenter of extensive criticism regarding both microbiological and chemical safety. This criticism has been intensified due to the recent outbreaks linked with Kimchi consumption; the first one took place in 2012 and was caused by enterotoxigenic Escherichia coli O169 while the second occurred in 2013 and was caused by norovirus GI.4 (Cho et al., 2014; Park et al., 2015). From a microbiological point of view, it has been widely accepted that lactic acid fermented foods are not a common vehicle of foodborne pathogens due to the antagonistic effect of the LAB; however, several studies as well as these outbreaks, have highlighted that such generalizations may be uncertain for reasons referring to both the raw materials and the adaptability of the pathogens (Burnett et al., 2000; Takeuchi and Frank, 2000, 2001; Beuchat, 2002; Klerks et al., 2007; Kroupitski et al., 2009, 2011; Mitra et al., 2009; Critzer and Doyle, 2010; Warriner and Namvar, 2010). Therefore, the ability of pathogenic bacteria to survive and proliferate during kimchi fermentation or storage has been studied to some extent.

Inatsu et al. (2004) assessed the survival of E. coli O157:H7, Salmonella Enteritidis, Staphylococcus aureus, and Listeria monocytogenes in both commercial and laboratory-prepared kimchi. Both types were inoculated with 5–6 log CFU/g of the pathogens and incubated at 10°C for 7 d. It was reported that all pathogens were able to survive. Moreover, only upon prolongation of the incubation did the population of the pathogens decreased to the enumeration limit. More accurately, S. aureus reached enumeration limit after 12 d, whereas S. Enteritidis and L. monocytogenes after 16 d. On the contrary, E. coli O157:H7 population remained at high levels throughout the 24 days of the experiment. These results were taken into consideration by Kim Y. S. et al. (2008) who applied heat treatment (85°C for 15 min) or a neutralization treatment (pH 7) at days 0 or 3 of kimchi fermentation in order to study the effect on Bacillus cereus, L. monocytogenes and S. aureus inoculated at 4–5 log CFU/g. Heat treatment at day 0 was more effective against L. monocytogenes, whereas at day 3 resulted in the complete inactivation of L. monocytogenes, significant population reduction of B. cereus but only marginal of S. aureus.

On the other hand, neutralization treatment at day 0 resulted in complete inactivation of S. aureus and significant decrease of L. monocytogenes population. However, upon neutralization treatment on day 3, complete inactivation of L. monocytogenes and significant decrease of S. aureus counts were observed. This issue was also assessed by Cho et al. (2011). In that study, the initial mixture of soongchimchae, i.e., a type of kimchi that combines fermented vegetables and meat, was spiked with 3–5 log CFU/g E. coli O157:H7 and L. monocytogenes and allowed to ferment at 4°C for 15 d. Both E. coli O157:H7 and L. monocytogenes counts gradually decreased during fermentation and were below detection limit after 14 and 15—post fermentation days, respectively.

The high incidence of stomach cancer among Koreans raised some concerns regarding dietary habits. This high incidence was linked to the consumption of soybean paste due to aflatoxin content (Crane et al., 1970). This triggered a huge debate whether soybean paste as an ingredient and kimchi itself may be regarded as risk or protective factors (Kim et al., 1985; Messina et al., 1994; Lee et al., 1995; Kim H. J. et al., 2002; Kim J. H. et al., 2002; Nan et al., 2005; Wang et al., 2015).

From a food hygiene perspective, aflatoxin accumulation should be avoided by any possible means. Additionally, studies like the one by Park et al. (2003) that reported aflatoxin B1 and G1 gradual degradation to 80–90% after 2 months of Doenjang fermentation and 100% after 3 months of fermentation, as well as the potential of LAB to bind aflatoxins (Haskard et al., 2001; Peltonen et al., 2001; Lahtinen et al., 2004; Bueno et al., 2007; Hernandez-Mendoza et al., 2009) and concomitantly remove them from the medium, should be further exploited. Similarly, controversial debates related to the nitrates, nitrites, ethyl carbamate, secondary, and biogenic amines content of Kimchi are currently ongoing (Kim et al., 2000; Haskard et al., 2001; Peltonen et al., 2001; Lahtinen et al., 2004; Mah et al., 2004; Bueno et al., 2007; Hernandez-Mendoza et al., 2009).

Kimchi is recognized worldwide for the number of health claims that have been made (Figure 3). It was presented in Health Magazine in 2006 as one of the world's five healthiest foods (Lee G. I. et al., 2012; Park et al., 2014; Dharaneedharan and Heo, 2016; Tamang et al., 2016). These health benefits result from the utilization of raw materials of high nutritive value and the microbiota prevailing the fermentation. Brassicaceae vegetables have been reported to contain a number of compounds with health-promoting potential, including dietary fibers, minerals, amino acids, vitamins, carotenoids, glucosinolates, and polyphenols.

The nutritive content of Chinese cabbage [Brassica rapa L. pekinensis (Lour.) Olsson] in particular has been extensively studied; presence of vitamins A and C, 34 amino acids with threonine, arginine, γ-aminobutyric acid, alanine, asparagine, serine and glutamic acid being quantitatively the most important, 10 mineral elements among which Ca, Mg, K, Na in higher relative abundance, lutein and β-carotene as the major carotenoids has been reported with the variations in the presented values being assigned to genetic diversity, agricultural practices, harvesting stage, tissue as well as determination method (Wills and Rangga, 1996; Singh et al., 2007; Watanabe et al., 2011; Kim et al., 2014; Bhandari et al., 2015).

Therefore, the raw materials used in the preparation of kimchi result in the increased nutritional value, i.e., the high levels of vitamins such as vitamin C, b-carotene, vitamin B complex, etc., minerals such as Na, Ca, K, Fe, and P, dietary fiber, and other various functional components such as allyl compounds, gingerol, capsaicin, isothiocyanate, and chlorophyll.

The phytochemicals such as indole compounds, b-sitosterol, benzyl isothiocyanate, and thiocyanate are the important active compounds found in kimchi, which have been reported to possess various medicinal potentials such as antiobesity, anticancer, antioxidant, and anti-atherosclerotic properties (Park and Rhee, 2005; Ahn, 2007; Park et al., 2014). In recent years, research has been focused on the polyphenolic and glucosinolate content due to the accompanying health claims that include protective effects against various types of cancer, cardiovascular and neurodegenerative diseases (van Poppel et al., 1999; Cohen et al., 2000; Kil, 2004; Stoclet et al., 2004; Scalbert et al., 2005; Kim et al., 2007; Singh et al., 2008; Han et al., 2011; Albarracin et al., 2012; Del Rio et al., 2013; Rodríguez-Mateos et al., 2014).

In Tables 3, 4 the polyphenolic and glucosinolate content of Chinese cabbage are presented, respectively. Regarding the former, sinapic acid has been reported as the major phenolic compound whereas gluconapin, progoitrin and glucobrassicin have been reported as the major glucosinolate (Mattila and Hellstrom, 2007; Chen et al., 2008; Kim et al., 2010; Cartea et al., 2011; Hong et al., 2011; Lee et al., 2014; Seong et al., 2016). In both cases the fluctuation presented is due to the analysis of different edible parts, varieties, or cultivars.

Apart from Chinese cabbage, radish, and onion are very often added to the mix, both of which are very important sources of dietary phytochemicals such as polyphenols, thiosulfates, and anthocyanins (Manach et al., 2004; Mattila and Hellstrom, 2007; Slimestad et al., 2007; Tedesco et al., 2015). Onion is a major source of flavonoids, particularly quercetin glucosides (Srinivasan, 2014) with reported anti-inflammatory (Gerates et al., 2007; Bureau et al., 2008; Lee et al., 2010; Endale et al., 2013; Yang D. et al., 2015) and anti-carcinogenic (Djuric et al., 2012) action.

Capsaicin and piperine are the major ingredients of red and black pepper, respectively. The antioxidant activity of both substances has been well documented (Pramanik et al., 2011; Arcaro et al., 2014). Garlic is rich in organosulfur compounds known for their antiinflammatory (Kumar et al., 2013; Schäfer and Kaschula, 2014) anticarcinogenic (Wang et al., 2012; Borkowska et al., 2013; Capasso, 2013) and cardioprotective potential (Stabler et al., 2012; Ried et al., 2013). Finally, a wide range of biological activities including anticancer (Ishiguro et al., 2007; Karna et al., 2012; Yang et al., 2012; Brahmbhatt et al., 2013) and antioxidant ones (Stoilova et al., 2007) have been assigned to ginger.

The potential for weight control in both mice and humans has been adequately documented. In the first case the antiobesity action that was accompanied by several other effects such as reduction of adipose tissue weights, adipocyte size, and inflammatory response in epididymal fat tissues, regulation of serum lipid profiles, insulin, eptin, and adiponectin levels, hepatic lipogenesis were assigned to the use of Ln. mesenteroides strain DRC 0211 (Cui et al., 2015) and W. koreensis strain OK1-6 (Park et al., 2012). The potential of Ln. kimchi strain GJ2 was described by Jo et al. (2015). In that study, a high-fat and high-cholesterol diet supplemented with kimchi made with the use of the aforementioned strain was fed to rats. A significant reduction of serum total cholesterol, triglyceride, low-density lipoprotein cholesterol levels, the atherogenic index, cardiac risk factor and triglyceride and total cholesterol levels in liver and epididymal adipose tissue were observed. Similar effects were observed by Kim E. K. et al. (2011).

Various researchers have indicated that consumption of kimchi on regular basis helps to decrease the level of cholesterol in the body (Kim and Lee, 1997; Kil et al., 2004). In the latter study, ingestion of fermented kimchi exhibited a series of positive effects on a variety of factors associated with metabolic syndrome, including systolic and diastolic blood pressures, percent body fat, fasting glucose, and total cholesterol, compared with the fresh kimchi suggesting that fermentation provides additional favorable effects for improving metabolic parameters. The red pepper powder used in kimchi is rich in capsaicin, which can cause loss of body fat by stimulating spinal nerves and activates the release of catecholamines in the adrenal glands of the body (Park et al., 2014). This compound increases the body metabolism and thus decreases the fat content (Yoon et al., 2004). Moreover, Kim E. K. et al. (2011) suggested that the consumption of fermented kimchi may affect obesity, lipid metabolism and inflammatory processes in human as well.

Furthermore, there are a number of health benefits with consumption of Kimchi as a part of the daily diet (Choi et al., 2015; Tamang et al., 2016). The antiaging potential of kimchi in the brain of senescence-accelerated mouse was reported by Kim J. H. et al. (2002) and using stress induced premature senescence of WI-38 human fibroblasts challenged with hydrogen peroxide was reported by Kim B. K. et al. (2011). Kimchi may have important role in delaying aging through the reduction of free radical production and increase in anti-oxidative enzyme activities. Similarly, kimchi also possess antibacterial potential that has been attributed to the presence of sulfur containing compounds and various LAB (Kil et al., 2004). The kimchi supplemented with Korean mistletoe extract had greater anticancer potential (80% inhibition ratio) than the kimchi without Korean mistletoe extract (62%) against the HT-29 human colon carcinoma cells (Kil, 2004). Likewise, different kinds of salt, natural sea salt (NS) without bittern or baked salt used to increase the taste of kimchi have been reported to increase the anticancer potential of kimchi as well (Han et al., 2009). Consumption of kimchi on a regular basis helps to increase the immune cell development and growth (Kim et al., 1997; Wu et al., 2000).