Course:FNH200/Projects/2020/The fermentation process

The Fermentation Process - Sauerkraut & Kimchi

History of Fermented Foods

Dry Yeast

Fermented foods have been in production for millennia. Wine making is believed to date back to roughly 6000 BCE, and cheese making dates back to 7000 BCE in the near east. Yogurt type foods such as the Indian Dahi dates back to roughly 6000-4000 BCE, and it is believed that the Egyptians were the first to produce leavened breads using yeast in about 4000 BCE.

Sauerkraut, a fermented form of cabbage dates back to the roman empire, in which it served as a nutrient rich preserved food to consume during the winter months. Sauerkraut is most well known as an Eastern or Central European food but is consumed worldwide, and is growing more popular in recent years .

Even though fermentation practices have been in place for a very long time, it was not until much later that scientists recognized the process by which fermentation occurs. Only after Antoine van Leeuwenhoek first observed bacteria in the 1600’s CE did research on fermentation begin to accelerate. Even French scientist Louis Pasteur studied fermentation in the 1800’s and coined it as ‘la vie sans l’air’ (life without air). His research, while profound, was only the start of a long scientific discussion on fermented foods. 

Fermentation was a fairly simple process which small communities engaged in for millennia. In the early days, some foods fermented naturally, and others were fermented with the help of yeast. At the time of the industrial revolution, fermentation was transformed from small community practice to large scale commercial production of products like wine and beer, and fermented meat and vegetables .

Almost every culture’s cuisine includes their own form of fermented food, whether it be alcoholic beverages, meats, leavened breads, cheese, and more. In Canada, Indigenous people have been fermenting food for generations; for example the production of igunaq, fermented walrus (or sea mammal) meat.

The Fermentation Process: Kimchi and Sauerkraut

The Fermentation Process

Fermentation Process Overall

Fermentation is an anaerobic process for breaking down glucose, with an extraction pathway of glycolysis . Moreover, in fermentation the pyruvate does not continue through oxidation and the citric acid cycle, and the electron transport chain does not run . The NADH (glycolysis) cannot drop its electrons off to turn back into NAD+, introducing fermentation as a mechanism to regenerate the electron carrier NAD+ from the NADH produced in glycolysis .

Lactic Acid Fermentation

Lactic acid fermentation is a method used by animals and some bacteria . In lactic acid fermentation, the process needed to make foods such as sauerkraut and kimchi, starts with NADH transfers its electrons directly to pyruvate, generating lactate; the corresponding enzyme for this reaction is lactase dehydrogenase .

The chemical reaction of lactic acid fermentation:

Pyruvic acid + NADH ↔ lactic acid + NAD + Pyruvic acid + NADH ↔ lactic acid + NAD+

Fermentation Process of Kimchi

In terms of fermentation, this section will present a small introduction of the traditional process of kimchi. Fresh cabbage is shredded, soaked in brine of approximately 10% salt concentration, and then washed and drained to later be packed, buried in the ground, and pressed with a stone in order to submerge them in the juice. Winter kimchi is fermented for 1-2 months and consumed for 3-4 months until the end of the spring season. Optimum taste is attained when it reaches a range of 4.0-4.5 of the pH and a range of 0.5-0.6 of acidity. Before-ripening, L. mesenteroides is the dominant microorganism, whereas Lactobacillus species are the major organisms in over-ripened kimchi.

Kimchi fermentation may be divided into four stages on the basis of the acidity produced:

• Initial stage with acidity <0.2%
• Immature stage with acidity between 0.2 and 0.4%
• Optimum-ripening stage with acidity between 0.4 and 0.9%
• Over-ripening or rancid stage with acidity >0.9%

The dominating lactic acidic bacteria are responsible for the production of the acidity, through fermentation of the available carbohydrates, without discouraging the type and quality of the raw materials, fermentation conditions which affect the process. Low temperature is preferred to prevent the production of high amounts of lactic acid, over-ripening, and the extension of the period of optimum taste

Fermentation Process of Sauerkraut

Fermentation of sauerkraut, can be summarized into different phases. The first phase would involve anaerobic bacteria starting the process of fermentation and the production of acidic environment to encourage the growth of bacteria .This stage can take around 3 days, after the cutting, salting and processing the cabbage, also as aerobic microbes are active, there is a drop of oxygen Which leads us to the second phase, which starts an acidic environment suppressing the growth of most of bacteria (including food-spoilage and food-borne diseases) not counting Leuconostoc mesenteroides and other Leuconostoc which thrive in this environment . Lactobacillus mesenteroides is of special importance in initiating the lactic acid fermentation, in combination with acid, acetic acid, ethanol, CO2, mannitol, dextrans and esters which are synthesized for around lasts 3–6 days . In the third phase, various Lactobacillus species(L. brevis and L. plantarum) further lower the pH while developing the flavour . The lactic acid concentration rises to 2.5% and the pH is lowered to 3.6–3.8. This period is dominated by heterofermentative lactic acid strains like L. brevis, Pediococcus and Enterococcus .

Canadian Food Regulations

Standardized Foods

The Canadian Standards of Identity was established for certain food products that must withhold a specific compositional standard. This may include a list of ingredients, manufacturing requirements, permitted food additives, fortification and food safety requirements.

In order to label a food product using the food’s common name (e.g., Sauerkraut) it must meet all listed requirements (if any) under the Canadian Standards of Identity.

Kimchi is not recognized as a standardized food in Canada.

In the Canadian Standards of Identity: Volume 4 - Processed Fruit or Vegetable Products, Sauerkraut is listed as a Standardized food in Canada. Therefore, the manufacturers of Sauerkraut food products must meet the requirements in order to label the product by its common food name.

In Canada, Sauerkraut with Preservatives may contain:

• Water
• Salt
• Seasoning and spices
• Natural flavouring ingredients
• Lactic acid

For more information on Sauerkraut as a Standardized Food in Canada, please visit The Canadian Standards of Identity.

Ingredients

Cabbage

Sauerkraut is a fermented food made primarily of cabbage with the addition of salt.

These two ingredients combined, along with proper conditions, create the perfect environment for the fermentation process to occur and to encourage the production of Lactobacillus bacteria that converts sugars into lactic acid.

Other common fermented cabbage food products such as kimchi, use the same starting ingredients as sauerkraut but also include additional ingredients such as spices to enhance the flavour profile.  

Lactic Acid Structure

Table 1: Sauerkraut & Kimchi Ingredients

Brand Name	Ingredients
Kühne Sauerkraut	White cabbage salt
Eden Organic Sauerkraut	Organic Cabbage Water Sea Salt Lactic Acid
Eden Organic Kimchi	Organic Cabbage Organic Red Bell Peppers Water Organic Onion Sea Salt Organic Dried Garlic, Organic Ginger Root Organic Cayenne Pepper Organic Mustard Seed Organic Chili Pepper Lactic Acid

Table 1: Kimchi includes additional spices such as red bell peppers, onion, dried garlic, ginger root,

cayenne pepper, mustard seed and chili pepper to impart specific flavours.

Table 2: Food Additives

Food Additives	Function of Additive in Product
Lactic Acid	Lactic acid is used to lower the pH in order to increase shelf-life and increase any further fermentation.

Table 2: Lactic Acid is an organic acid naturally produced during the fermentation process of Sauerkraut and other fermented foods such as kimchi. Lactic acid can be added to enhance flavour, adjust pH levels and preserve the food product.

Lactic acid is produced by lactic acid bacteria (Lactobacillus bacteria) to produce specific compounds that possess important roles in the fermentation process that impart many of the sensory characteristics of fermented foods such flavour and acidity. For instance, the lactic acid bacteria produce the organic compound lactic acid which contributes to the slightly sour flavour of sauerkraut and kimchi and acts as a natural preservative to extend shelf life. More importantly, lactic acid bacteria also contributes to human health due to its ability to act as probiotics.

Sauerkraut Recipe

Homemade Sauerkraut in Glass Jar

Table 3: How to Make Sauerkraut!

	Sauerkraut
Ingredients	25 lbs cabbage 3/4 cup pickling salt
Procedure	Work with about 5 pounds of cabbage at a time and discard outer leaves. Rinse cabbage heads under cold running water and drain. Cut cabbage heads into quarters and remove cores. Shred or slices cabbage to a thickness of a quarter. Put cabbage into a suitable fermentation container. Add 3 tablespoons of salt. Mix thoroughly with clean hands. Pack cabbage firmly until the salt draws out the juices. Repeat until all cabbage is in the container. Leave 4 or 5 inches above the cabbage to the rim. Juice should be covering the cabbage if not, add boiled and cooled brine (1-1/2 tablespoons of salt per quart of water). Add plate and weights over container with clean bath towel. Allow to fully ferment and then enjoy!
Storage	For good quality sauerkraut store at 21° to 24°C and will be fully fermented in 3 to 4 weeks. Storage at 16° to 18°C will take 5 to 6 weeks to fully ferment. Temperatures lower than 16°C may result in no fermentation. Temperatures above 24°C may result in sauerkraut becoming soft. Fully fermented sauerkraut may be kept stored for several months in an air tight container in the refrigerator.

Table 3:

• Pickling salt is recommended for making sauerkraut. Pickling salt does not contain iodine or anti caking products.
• Suitable fermentation containers include food-grade plastic and glass containers. Fermentation containers must be washed in hot water with dish soap and rinsed well in very hot water before use. This step is crucial to ensure no contamination.

For more information on Preparing Fermented foods, please visit the National Center for Home Food Preservation.

Storage

Even though fermentation is primarily a type of preservation to enhance the longevity of the product, storage plays a huge role in the quality of the final product in terms of nutritional value, physical appearance, texture, flavor, aroma, etc.

When sauerkraut started started to gain its popularity in the western world, scientists held experiments on the different storage environments that would allow sauerkraut to retain its prime qualities.

A very important factor to consider during the fermentation of sauerkraut is proper packaging, “multi-layered plastic sheeting on top of the sauerkraut weighted won by water provides an  excellent seal during the storage period” . This ensures that no air enters during storage as air could cause chemical changes to the product such as oxidative deterioration (especially if sauerkraut is not fully emerged in liquid), since oxidative reactions happen faster in gas compared to liquid. These reactions can result in a darker appearance of the product as well as a change in flavor. These reactions however can be halted or delayed if ascorbic acid is present. Due to the low pH nature of fermented sauerkraut, microbiological changes don’t occur that often, unless oxygen is present. The first indicator of microbiological changes is a thin cream-colored film of yeast on the surface, coupled with a yeasty odor.

The three main factors that should be taken into consideration during storage is pH, temperature, and exposure to oxygen. Results of this study show that the viability of most fermented foods is best maintained at low temperatures which can be achieved by freezing and refrigeration. For short storage (a period of time less than 3 months) cooling and freezing and refrigeration will achieve the same level of preservation of required microorganism keeping the fermented product viable. However for periods longer than 6 months, only freezing will preserve the fermented product successfully. Storage temperatures between -20°C and 4°C are the most suitable for storage of fermented products. Optimum pH value vary as each fermented product has its unique variety of microorganisms with varying optimum pH levels.  hence optimum pH should be maintained throughout the storage process, at temperatures between -20°C and 4°C, and packaging should ensure minimal exposure to air.

Packaging

Kimchi packaging with one-way air valve

Packaging is important for food preservation. The design of packaging influences the shelf life and the quality of the food. Especially for fermented food, the packaging as a barrier aims to separate the food and the external atmosphere. It also influences the growth of the microorganism within the container and further influences the food quality.

Since fermented food requires anaerobic conditions, the packaging should be low oxygen permeability in order to provide anaerobic conditions to encourage the growth of desirable microorganisms. Fermented food used to package in vacuum or modified atmosphere glass containers, such as wine. Later on, due to the cost and transportation, plastic containers become more popular in food packaging since they are cheap, flexible and also have low moist permeability.

In some of the fermented food, carbon dioxide is released during the growth and metabolism of the alcohol and acid-producing microorganisms. The packaging design also needs to deal with it to avoid the food being over fermented and the container being expanded by the excess carbon dioxide. Therefore, the packaging should be also breathable.

Take kimchi as an example, the microorganism produces organic acid and carbon dioxide. The carbon dioxide would aggregate at the top of the containers. If the gas wasn’t released to the external atmosphere, the container might be expanded or leakage over time. Therefore, some commercial kimchi products have carbon dioxide or gases absorbent sachet attached to the inside of the packaging, some have degassing valves on the packaging to release the excess carbon dioxide.

Labeling

In the Canadian Food Labeling Requirement, fermentation is regarded as the minimum process. The fermented products can not claim as natural or nature on the label. Although the food additives or microorganisms used in fermentation is natural, the food product cannot be labelled as nature or natural product, neither in advertisements since the food or the ingredients of the food has been significantly changed their original structure either in physical, chemical or biological . Besides the mandatory information, such as ingredient list and nutrition facts (more information in Food labeling for industry), there are no other specific requirements for fermented food labeling.

Sauerkraut is one of the fermented foods but also is identified as a processed vegetable product in Canadian Standards of Identity: Volume 4 – Processed Fruit or Vegetable. According to Labeling Requirements for Processed Fruit and Vegetable, the packaging of sauerkraut with preservative should label "Keep Refrigerated" and "garder réfrigéré" on any part of the label other than the bottom of the container. Since kimchi is not a standardized food in Canada, there is no special label requirement for it.

Label description for Sauerkraut

Common Name	There is no other common name, hence the packing clearly shows the name "Sauerkraut" along with the Brand name.
Country of Origin	Not required but local Canadian made products contain a "Product of Canada" label.
Bilingualism	Both English and French descriptions are found on the Canadian made Kuehne Brand label, including ingredients, nutrition facts, claims and storage instructions.
Date Markings and Storage Instructions	Best before date is clearly marked on the top. There are no specific Storage Instructions present.
Name and Principle Place of Business	The name and address of the producer is labelled. For example; Eden Foods have their Michigan Address clearly labelled.
Legibility and Location	Legibility: All labels are clear to read. The text color is different from the background color. For example, the Nutrition facts label has white background and black text. Location: Common name and net quantity are labelled correctly on principal display panel Nutrition facts are labelled continuously on the display panel. Ingredients are labelled next to nutrition facts, and not at the bottom. Durable life date, name and principal place of business are labelled on the display panel.
Net Quantity	All types of packaging include net quantity in all types such as OZ, Lbs, g.
Nutrition Facts	All types of packaging include nutrition facts.
Irradiation	No irradiation is marked on the package. (Product is not irradiated.)
List of Ingredients and Allergens	Has a clear list of ingredients. The ingredients are listed in descending order of proportion by weight. No allergens are labelled on the packaging.
Sweeteners	No sweeteners are marked on the package.
Food Additives	Food additives (Lactic Acid) is listed by the ingredients but not specifically labelled as an additive.
Claim and Statements	Eden Organic Sauerkraut claims a "Double Organically grown Certified" sticker.

The back including the ingredients and other information>

The Front including the Brand name, common name and claims                                                                                                                    

Benefits of Fermentation

Table 4: Advantages & Disadvantages of Fermentation

Advantages	Disadvatages
Acts as a biological method of food preservation. Reduced risk of contamination owing to the anti-microbial end-products such as organic acids and ethanol. Allow for variety in our diets as fermented foods create new and desirable tastes and textures. Can promote human health such as improving the immune system and intestinal health.	Slow process. If done without proper sanitation methods, can increase contamination.

Reflection

As a group, we were happy with what we accomplished and learned regarding the fermentation process. Thus we accomplished what we set out to do at the beginning. Each of us covered different areas of interest, for example the history of fermented foods or the process behind it. We also learned a recipe to make sauerkraut. We were able to explore our areas of interest and practical application and relate them with the class material. This was possible with our commitment and a bit of Judy’s guidance!

Throughout this project, we were able to dive deeper into the fermentation process and explore more in depth different fermented foods such as sauerkraut and kimchi.  

We met through Zoom meetings on regular intervals during the project timeline to discuss the project development. Every meeting was essential for the progress of the project, as we cared for the well-being of our team mates, but making sure everyone was able to work at their own pace. Overall, the team communication was very efficient and made the project flow smooth.

In terms of what we would have done differently, our group was actually quite satisfied with the way that this project worked. We chose a topic and food applications that really interested us, so at the end, we couldn’t think of anything that we didn’t accomplish. We faced some difficulties due to the nature of online learning and different time zone/work/school schedules, but we were still able to meet and work together and we are happy with the finished result. Our system of regular meeting and individual work in between worked well as we all were accountable for our parts, but on our own schedules.

Exam Question

Which microorganism is responsible for the fermentation of sauerkraut?

a) Yeast

b) Propionibacterium shermanii

c) Lactic acid bacteria (Lactobacillus bacteria)

d) Penicillium roquefortii

The correct answer is c). Lactic acid bacteria is a key component of the fermentation process in many foods. Answers b) and d) are secondary bacteria added to cheeses, Swiss and Blue respectively, to impart specific characteristics on the cheese. Yeats are used in the making of bread and alcohol.

The answer to this question and other microorganisms responsible for fermentation can be found in table 9.1 in section 9.3 on Fermentation.

The final exam should reflect on important topics discussed on the course. Fermentation is an umbrella term for many processes and microorganisms that work together to keep us healthy and allows us to enjoy our food. We believe that students should know one of the specific microorganisms that produces sauerkraut (a well known food).