Fermentation is a process which involves slow decomposition of organic substances, induced by enzymes or microorganisms, that basically convert carbohydrates into organic acids. Fermented foods and beverages have a diversity of traditions and cultural preferences based on the geographical areas from which they have originated. Fermentation allowed our ancestors from temperate and cooler regions to survive in the winter season and those from the tropics to survive drought periods. The production methods of such fermented food and beverages were unknown and passed down from one generation to another as family traditions.
The processes of fermentation are believed to have been developed and used in order to preserve vegetables and fruits for times of shortage; by preserving the food by alcohols and organic acids and also to give the food desirable texture and flavor. Fermentation also aids in reducing toxicity (remove antinutritional factors) and the cooking time. Drying and salting are standard fermentation processes in some of the oldest methods of food preservation. Fermentation stands to be one of the oldest food processing techniques to extend the shelf life of spoilable food before the advent of refrigeration.
World Health Organization (WHO) recommends the consumption of a healthy amount of vegetables and fruits in our daily food to prevent diseases such as hypertension, coronary heart problems and to reduce the risk of strokes. Even though, consumers normally tend to prefer food and beverages which are fresh, nutritional and ready to consume, lactic acid (LA) fermentation of vegetables and fruits is a practice that is commonplace to maintain and improve nutritional and qualitative aspects of food.
The world population crisis is real and as it increases, lactic acid fermentation is conceived to play a major role in preserving fresh fruits, vegetables, and other food items necessary for feeding people in developing and underdeveloped countries. Among the food items, fruits and vegetables are more vulnerable to spoilage due to their nutritional properties and their high water content. These perishable conditions are further fuelled in tropical and subtropical countries which are more conducive to the growth of spoilage-causing microorganisms.
Fermented fruits and vegetables can be utilized as potential probiotics as many lactic acid bacteria such as Lactobacillus plantarum, L.pentosus, L.brevis, L.acidophilus, L.fermentum, Leuconostoc fallax, and L.mesenteroides are found in them. The word probiotic means “for life” and is generally attributed to the bacteria associated with health benefits for humans. Many studies conducted on probiotics implicate them in health benefits upon consumption such as improved intestinal balance and function, lowering of serum cholesterol, enhanced immunity and reducing the risk of colon cancer. So, fermented fruits and vegetables possess the quality of not just being a viable food supplement but can have a direct and indirect impact on our health.
Overview of the fermentation process of fruits and vegetables
The following are some of the most reported fermented fruits and vegetables and they are classified as follows:
- Root vegetables: carrots, turnips, beetroot, radishes, celeriac, and sweet potato.
- Vegetable fruits: cucumbers, olives, tomatoes, peppers, okra, and green peas.
- Vegetable juices: carrot,turnips,tomato pulp,onion, sweet potato,beet,and horseradish.
- Fruits: apples, pears, immature mangoes, immature palms, lemons, and fruit pulps such as banana.
Traditional fermented fruits and vegetables of Indian origin
Traditional fermented foods are popularly consumed and are an integral part of the Indian diet since time immemorial. The Indian subcontinent is traditionally rich in fermented foods and they are prepared using local food crops and other biological resources. Each fermented food is associated with characteristic microbiota which can have its own effect on the type, kind and levels of vitamins, proteins, fatty acids, and essential amino acids.
Especially, in eastern Himalayan regions of India, different types of traditional fermented vegetable products are prepared as a means of bioprocessing the spoilable vegetables for storage and subsequent consumption. Let us take a look at some of these products and their properties.
- Gundruk is a nonsalted, fermented, and acidic vegetable product indigenous to the Himalayas.
- During fermentation of gundruk, fresh leaves of local vegetables known as rayosag , mustard leaves, cauliflower leaves, and cabbages are wilted for 1-2 days.
- Wilted leaves are crushed mildly and pressed into a container or earthen pot made airtight and fermented naturally for about 15–22 days.
- After desirable fermentation, products are removed and sun-dried for 2–4 days.
- Gundruk is consumed as pickle or soup and has some resemblance with other fermented acidic vegetable products such as kimchi of Korea, sauerkraut of Germany, and sunki of Japan.
- The predominant microflora of Gundruk includes various LAB(Lactic Acid Bacteria) such as L. fermentum, L. plantarum, L. casei, L. casei subsp. , pseudoplantarum, and Pediococcus pentosaceus.
- Sinki, an indigenous fermented radish taproot food, is traditionally prepared by pit fermentation, which is a unique type of biopreservation of foods by LA fermentation in the Sikkim Himalayas.
- For sinki production, a pit is dug with 2-3 ft diameter in a dry place. The pit is cleaned, plastered with mud, and warmed by burning. After removing the ashes, the pit is lined with bamboo sheaths and paddy straw.
- Radish tap roots are wilted for 2-3 days, crushed, dipped in lukewarm water, squeezed, and pressed tightly into the pit, covered with dry leaves and weighted down by heavy planks or stones. The top of the pit is plastered with mud and left to ferment for 22–30 days.
- After fermentation, fresh sinki is removed, cut into small pieces, sun-dried for 2-3 days, and stored at room temperature for future consumption. Pit fermentation has been practiced in the South Pacific and Ethiopia for the preservation of breadfruit, taro, banana, and cassava.
- Sinki fermentation is carried out by various LAB including L. plantarum, L. brevis, L. casei, and Leuconostoc fallax.
- Khalpi or khalpi is a fermented cucumber (Cucumis sativus L.) product, commonly consumed by the Brahmin Nepalis in Sikkim.
- It is the only reported fermented cucumber product in the entire Himalayan region. Ripened cucumber is cut into suitable pieces and sun-dried for 2 days, and then put into a bamboo vessel and made airtight by covering with dried leaves.
- It is fermented naturally at room temperature for 3–5 days. Fermentation after 5 days makes the product sour in taste. Khalpi is consumed as pickle by adding mustard oil, salt, and powdered chilies. Khalpi is prepared in the months of September and October.
- Microorganisms isolated from Khalpi include L. plantarum, L. brevis, and Leuconostoc fallax
- In Northeast India, especially the people of Nagaland and Manipur consume Inziangsang, a traditional fermented leafy vegetable product prepared from mustard leaves and similar to gundruk.
- The preparation process of inziangsang is like of gundruk. Mustard leaves, locally called hangam (Brassica juncea L. Czern), are collected, crushed, and soaked in warm water. Leaves are squeezed to remove excess water and pressed into the container and made airtight to maintain the anaerobic condition.
- The container is kept at ambient temperature (20°C–30°C) and allowed to ferment for 7–10 days. Like gundruk, freshly prepared inziangsang is sun-dried for 4-5 days and stored in a closed container for a year or more at room temperature for future consumption.
- Nagaland people consume inziangsang as a soup time with steamed rice. In the resident meal, the fermented extract of ziang dui is used as a condiment. This fermentation is also supported by a set of LAB which includes L. plantarum, L. brevis, and Pediococcus.
- Soidonis a widespread fermented product of Manipur prepared from the tip of mature bamboo shoots. The main source of fermentation is the tips or apical meristems of mature bamboo shoots.
- Outer casings and lower portions of the bamboo shoots were removed and whole tips are submerged in water in an earthen pot. The sour liquid (soijim) of a previous batch is added as a starter in 1: 1 dilution, and the preparation is covered. Fermentation was carried out for 3–7 days at room temperature.
- Leaves of Garcinia pedunculata Roxb. (family: Guttiferae), locally called heibungin in Manipuri language, may be added to the fermenting vessel during fermentation to enhance the flavor of soidon. After 3–7 days, soidon is removed from the pot and stored in a closed container at room temperature for a year.
- L. brevis, Leuconostoc fallax, and Lactococcus lactis take part in fermentation.
- Goyang, a prominent traditional fermented vegetable foodstuff of the Sikkim and Nepal, leafs of magane-saag(Cardamine macrophylla Willd.), belonging to the family Brassicaceae, are collected, washed, cut into pieces, and then squeezed to drain off excess water and are tightly pressed into bamboo baskets lined with two to three layers of leaves of fig plants.
- The tops of the baskets are then covered with fig plant leaves and fermented naturally at room temperature (15°C–25°C) for 25–30 days.
- L. plantarum, L. brevis, Lactococcus lactis,Enterococcus faecium, and Pediococcus pentosaceus, yeasts Candida spp., were LAB isolated from goyang.
This article fundamentally makes a case for preserving traditional knowledge and building upon it, and on how science can play a role in utilizing the vast potential that these fermented products, which are probiotic in nature, have to offer, in enhancing human health.
- Manas Ranjan Swain, Marimuthu Anandharaj, Ramesh Chandra Ray, and Rizwana Parveen Rani, “Fermented Fruits and Vegetables of Asia: A Potential Source of Probiotics,” Biotechnology Research International, vol. 2014, Article ID 250424, 19 pages, 2014. doi:10.1155/2014/250424
- Satish Kumar, R, P Kanmani, N Yuvaraj, K A Paari, V Pattukumar, and V Arul. 2013. “Traditional Indian Fermented Foods: A Rich Source of Lactic Acid Bacteria.” International Journal of Food Sciences and Nutrition 64 (4). Taylor & Francis: 415–28. https://doi.org/10.3109/09637486.2012.746288.
Disclaimer: The above article is sponsored by Thyrve, the world’s first Gut Health Program that incorporates microbiome testing and personalized probiotics to ensure a healthier gut, happier life, and a brighter future.