Black Garlic & it's Bioactive Compounds on Human Health Diseases
1. Introduction
With the prevalence of chronic diseases and their associated pathological complications, health has become the top of scientific research priorities, with the goal of finding novel foods and tactics to tackle such public health burdens. The scientific literature has recently witnessed flourishing pharmaceutical and nutrition research to use food plants for their diverse health advantages and possible therapeutic uses. A fundamental objective of this nutritional research is to give scientific knowledge to optimize health, and prevent or delay the development of illness. An increasing amount of scientific data suggests that dietary interventions, particularly those that provide high levels of plant foods, can prevent or delay the growth of chronic age-related pathologies by safeguarding the body’s critical physiological systems. The prohibitive effect of plant foods has been investigated as a novel therapeutic remedy for the presence of pharmacologically active substances. Besides, plant foods, and many of their derivative products, i.e., extract, contain various micronutrients (minerals and vitamins), fibers, and bioactive compounds, known as phytochemicals. Notably, plant-based dietary pattern foods have improved different intermediary outcomes with a lower incidence of chronic diseases, including cancer, cardiovascular, neurodegenerative diseases, modulate intestinal microbiota composition and functionality with a positive human health impact [1,2].
In the last few decades, single subgroups of botanical agents such as vegetables, fruits, herbs, and nuts, have been taken into consideration to use as nutrient supplements and recognized for their numerous health benefits, including the prevention of diseases [3,4,5]. Among these, garlic (Allium sativum) has been one of the most important dietary sources not only for health benefits but also as a traditional medicinal all over the world [6,7,8,9,10]. Despite all of the health benefits of garlic, the current global consumption of garlic is declining. Some people are unwilling to eat fresh garlic due to its pungent, offending taste and smell, and it can cause gastrointestinal discomfort in some people [11,12]. Therefore, researchers are trying to use raw garlic in different forms such as smocked garlic, garlic oil macerate, garlic juice, supplement pill, garlic powder, etc., to alleviate these discomforts [13,14].
Among the commercially available various garlic processing products, black garlic (BG) has been well known as the fastest-growing health food and is the most studied [15]. Although BG’s origin remains dubious, the product is believed to have been consumed in Korea, Japan, and Thailand from ancient times; in 2014, BG reported an estimated market value of around $94 million [16]. BG is a form of aged garlic obtained from raw garlic (Allium sativum) via the Millard reaction under high temperature (60–90 °C) and humidity (70–90%) for a period of time [17,18]. The offensive and harsh odor of fresh garlic are converted into a chewy texture and sweet taste during the aging process [19]. The aging process not only modifies the nutrients and sensory attributes of BG but also improves bioactivity. The health benefits of BG intake are largely associated with the presence of bioactive substances such as phenol and organosulfur. The bioactive components of BG display a wide variety of physiological functions in the human body, which may have therapeutic potential for treating various diseases. For instance, multiple studies showed the bioactivities of BG, including antioxidation [20], anti-inflammation [21,22,23], anti-obesity [24,25], hepatoprotection [26,27,28], hypolipidemia [29,30], anti-cancer [31,32,33], anti-allergy [34,35], immunomodulation [15,36], cardiovascular prevention [37,38], and neurodegenerative protection [39].
In the last few decades, substantial studies have been conducted on BG and its components against different common human diseases. Still, a lot of research is ongoing to find out the therapeutic effects of BG. However, a review of the health benefits of BG and its components on different common human diseases from fundamental to clinical studies is still lacking. Thus, in this review, we summarize the pre-clinical and clinical studies of BG and its bioactive compounds on human health diseases along with diverse bioactivity, the related mode of action, and also future challenges. We hope a comprehensive overview of published findings on the health benefits of BG and its bioactive compounds can help food and nutrition experts, researchers, and scientists define future research direction with clinical evidence to improve people’s health and wellness.
2. Data Collection
The authors of this review article carried out a literature search for relevant articles regarding BG effects on human diseases by determining sources or literature in the form of primary data or official books, national or international journals published till May 2021. Additionally, data searches were also conducted using different online platforms. During writing this review article, the main references were cited from the trusted source, such as Google Scholar, Web of Science, Scopus, NCBI, Science Direct, ResearchGate, Medline (PubMed), and other trusted journals publishers.
3. Thermal Processing of Black Garlic
The thermal processing of BG from raw garlic has been processed under controlled temperature and relative humidity without additives, which is ready to consume with a sweet taste and slightly pungent odor and taste. Currently, there is no standard procedure for producing BG; processing conditions vary greatly depending on regional traditions and the specific features desired in the ultimate product. Till now, researchers are trying to find out optimal conditions for BG processing and they have already applied different thermal processing plans (Table 1). BG is commonly processed in temperature ranges between 30–90 °C, 50–90% relative humidity, and an incubation period of 10–80 days