Course:FNH200/Projects/2021/Kefir

From UBC Wiki
Lifeway Kefir Non-Fat Alternative

Introduction

Kefir is a fermented milk product with yogurt-like consistency and cottage cheese-like appearance[1][2]. It is known to be beneficial for digestion, gut health, allergies, asthma, cancer and has shown to be a better probiotic than yogurt[3]. Kefir tends to be popular amongst certain populations such as athletes and babies as a way to prevent weight gain and increase immunity against diseases[4]. This drink is made of kefir grains which consist of colonies containing yeast, lactic acid bacteria and sometimes acetic acid bacteria[3][5]. This culture works via a process called fermentation which converts the sugars found within the milk into alcohol, as well as the lactose into lactic acid, thereby producing a sour taste[3]. Kefir is traditionally made of goat or cow milk, however, it can be made into a dairy-free alternative with sweet liquids such as coconut milk or coconut water[3]. Kefir products range from cheese, probiotic drinks, yogurt and even tarts[6]. Within those products many manufacturers produce low fat, non-fat, organic, protein-boosted and seasonal versions of Kefir[6]. Kefir can be used in numerous dishes such as smoothies, salad dressings, popsicles, ice cream, overnight oats, and breads or muffins[7][8].

Production of Kefir

Fermentation Tanks
Kefir Grains (containing colonies of bacteria and yeast)

Fermentation

Fermentation is commonly defined as a chemical change in a substrate that is brought about by using microorganisms (i.e. yeast and bacteria) under anaerobic conditions [9]. Humans have been controlling the fermentation process for thousands of years, and have an extensive history in the development of food and beverages[10]. The process of converting carbohydrates to alcohol or to organic acids using microorganisms can help limit the growth of harmful bacteria, extend the shelf-life, and give a unique “tangy” flavour to the food[11].  Kefir is a fermented milk beverage that is obtained by pasteurization, to remove endogenous microflora, and then a mixture of bacteria (Lactobacillus caucasius), along with 2 yeasts (Saccharomyces kefir and Torula kefir), are added [12][13][14]. The bacteria ferment the lactose in the milk to lactic acid via an endogenous lactase enzyme producing the “tangy” flavour, while the yeast can ferment the available sugars in milk to yield alcohol, CO2 and organic byproduct[12][13][14]. As a result of yeast fermentation, it gives the kefir a fizz and effervescence which contributes to its overall experience as a product[12][13][14].


Enzymes

Enzymes are proteins that act as catalysts in all living organisms (plants, animals, microorganisms and humans) which act to increase the rate of chemical reactions within biological systems[15]. Enzymes are generally thought about in terms of the substrate they break down (i.e. Amylase - breaks down starch, Protease - breaks down protein, and Lipase - breaks down lipids) although they are much more complex[15]. Kefir contains many digestive enzymes including lipases, proteases, lactases along with billions of probiotics[16]. Given the numerous enzymes present and bacteria fermentation processes, this product is often considered as “predigested” and is known to help ease digestion, add nutrients and increase vitamin uptake[16].

Health and Nutrition

Lifeway Kefir by Leslie Seaton

Nutritional Properties

Kefir is composed of several vitamins, minerals and essential amino acids that are crucial for homeostasis[5]. It contains vitamins A, B1, B2, B5, C, K and carotene[5]. The fermentation process alters the amino acid profile of kefir as well as the lactose content, there is less lactose but more B-galactosidase in kefir than milk, making it a good option for lactose-intolerant people[3][5]. Kefir also contains higher levels of threonine, serine, alanine, lysine and ammonia compared to milk. There are many other amino acids found in kefir including tryptophan, which plays an important role in the nervous system[5]. Kefir is a good source of minerals including calcium, magnesium, and phosphorus[5]. Phosphorus is the second most abundant mineral in the human body and it is involved in the utilization of carbohydrates, fats and proteins for cell growth, maintenance and energy[5].

Liberté Organic Kefir (Plain 1%)

Nutritional Facts

[Example: Liberté Organic Kefir (Plain 1%)]

Nutritional Facts Table (per 1 cup [250 mL])
Calories 70
Fat 3% of daily value
Saturate 6% of daily value
Cholesterol 10 mg
Sodium 105 mg (4% of daily value)
Carbohydrates 6g (2% of daily value)
Fibre 0 g
Sugars 6 g
Proteins 7 g

(Adapted from Liberté Organic Kefir (Plain 1%) website[17])

The ingredients for this product are simple, it contains fermented milk, and bacterial cultures[17]. It contains 10 strains of active cultures and provides 2 billion probiotics per 250 ml[17].

Health Benefits

Kefir has antibacterial, immunological, anti-tumoural, anti-carcinogenic and hypocholesterolaemic effects[5]. Probiotics works by enhancing the non-specific and specific immune response, production of antimicrobial substances and competition with pathogens for binding sites[18].

Storage and Packaging

Pasteurizing Plant

The safety and storage life of perishable food items (products that are minimally processed and have a shelf life of less than 60 days) such as kefir can be extended by pasteurization prior to packaging. Pasteurization is a type of thermal processing that involves the use of high temperatures for a short time period to inactivate both disease and spoilage-causing microorganisms. It also inactivates endogenous enzymes in food that can lead to food deterioration[19].  High-temperature short time (HTST) pasteurization is the most common form of industrial pasteurization for kefir[19]. This thermal process involves heating the milk to a target temperature of 70°C with a hold time of 20 seconds. Alternatively, ultra-high temperature processing (UHT) can also be used. In UHT, the milk is heated up to 135°C for a hold time of two seconds[20]. Spray cooling is subsequently used to cool the milk after pasteurization to help keep bacteria growth to a minimum. After pasteurization, the process of fermentation begins.

After fermentation, kefir is then ready to be packaged for retail sale. Kefir is commonly sold in plastic bottles and glass containers. Both types of packaging have their advantages and disadvantages. For example, glass containers let the consumers see the content, color, and texture of kefir. Additionally, glass is more resistant to corrosion and won’t react to the acidity of kefir[20]. However, one disadvantage is that glass is fragile and must be packaged with extra protection to prevent physical breakage during transportation. Plastic containers are convenient for transportation and can also be used with new UHT-aseptic packaging technologies. However, plastic is easily damaged compared to glass containers, and scratches in the plastic can shelter foreign bacteria leading to spoilage[20]. Both types of packaging use tightly sealed containers to minimize the amount of air. This helps to prevent the excessive growth of bacteria and mold[19].

Since kefir is a fermented beverage, it should be stored in the fridge and not at room temperature. Refrigeration prevents the liquid from continuing to ferment, thereby extending the storage length of the product[19]. Due to the presence of bacteria in kefir, it naturally has a shorter shelf life relative to other produce. The shelf-life depends on several factors, for example, homemade kefir tends to have a longer shelf-life than commercial bought kefir (2-3 weeks vs 1 week). If kefir is not kept in the fridge, it can spoil within a few days[21]. Some indicators of spoiled kefir include: presence of mold on the top, heavy separation (i.e. looks like water with solid chunks), sour smell and taste[21].

References

  1. ↑ Cook, Doug. "What Is Kefir And Is It Good For You?". Canadian Digestive Health Foundation. Retrieved July 27, 2021.
  2. ↑ "Kefir Health Benefits: Products With This Healthy Ingredient". The Huffington Post Canada. August 26, 2014. Retrieved July 27, 2021.
  3. ↑ 3.0 3.1 3.2 3.3 3.4 Leech, Joe (September 24, 2018). "9 Evidence-Based Health Benefits of Kefir". Healthline. Retrieved July 27, 2021.
  4. ↑ Ahmed, Zaheer; Wang, Yanping; Ahmad, Asif; Khan, Salman Tariq; Nisa, Mehrun; Ahmad, Hajra; Afreen, Asma (February 7, 2013). "Kefir and Health: A Contemporary Perspective". Critical Reviews in Food Science and Nutrition. 53: 422–434.
  5. ↑ 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 Arslan, Seher (November 24, 2014). "A review: chemical, microbiological and nutritional characteristics of kefir". CyTA - Journal of Food. 13: 340–345.
  6. ↑ 6.0 6.1 "Kefir". Lifeway. Retrieved July 27, 2021.
  7. ↑ Amidor, Toby (April 2015). "6 Surprising Ways to Use Kefir". Food Network. Retrieved July 27, 2021.
  8. ↑ Foster, Kelli (October 22, 2015). "5 Smart Ways You Could Be Using Kefir in Your Cooking". The Kitchn. Retrieved July 27, 2021.
  9. ↑ Wright, R (2005). "MASS SPECTROMETRY | Gas Analysis". Encyclopedia of Analytical Science (Second Edition): 366–374.
  10. ↑ Clime, Kelly. "Beyond Sauerkraut: A Brief History of Fermented Foods". Living History Farms. Retrieved July 27, 2021.
  11. ↑ "The Role of Fermentation in the Food Processing Industry". Klever Equipped Inc. Retrieved July 27, 2021.
  12. ↑ 12.0 12.1 12.2 Frias, Juana; Martinez-Villaluenga, Cristina; Peñas, Elena (2016). Fermented Foods in Health and Disease Prevention. Elsevier Inc. ISBN 978-0-12-802309-9.
  13. ↑ 13.0 13.1 13.2 Fuquay, John (2011). Encyclopedia of Dairy Sciences. Elsevier Ltd. ISBN 978-0-12-374407-4.
  14. ↑ 14.0 14.1 14.2 Batt, Carl; Tortorello, Mary Lou (2014). Encyclopedia of Food Microbiology. Elsevier Ltd. ISBN 978-0-12-384733-1.
  15. ↑ 15.0 15.1 "Enzymes used in Food Processing". Government of Canada. September 11, 2014. Retrieved July 27, 2021.
  16. ↑ 16.0 16.1 "Enzymes and Your Gut — You Aren't Just What You Eat, You're What You Digest and Absorb". Cultured Food Life. Retrieved July 27, 2021.
  17. ↑ 17.0 17.1 17.2 "Organic - Plain 1%". Liberté. Retrieved July 27, 2021.
  18. ↑ Singh, Varun Pratap; Sharma, Jagannath; Babu, Shankar; Rizwanulla; Singla, Anshul (February 2013). "Role of probiotics in health and disease: A review". Journal of the Pakistan Medical Association. 63: 253–257.
  19. ↑ 19.0 19.1 19.2 19.3 Potter, Austin; Middleton, Tamia. "Yogurt and Kefir Manufacturing". Visual Encyclopedia of Chemical Engineering. Retrieved July 27, 2021.
  20. ↑ 20.0 20.1 20.2 "Choosing Equipment for Making Water Kefir". Cultures for Health. Retrieved July 27, 2021.
  21. ↑ 21.0 21.1 Skrzypiec, Marcin (October 16, 2020). "CAN KEFIR GO BAD?". CAN IT GO BAD?. Retrieved July 27, 2021.

Exam Question

How is kefir considered a lactose-intolerant friendly product?

A) Enzymes and bacteria break down lactose during the fermentation process

B) The pasteurization process alters lactase to be less effective

C) It can be made without dairy

D) A and C

E) B and C

F) All of the above

**The correct answer is D. A and C are factual answers that can be found on the wiki page. B is incorrect as pasteurization kills bacteria that can be harmful for the product and consumers, and pasteurization does not have any affect on sugar metabolism.

**This question touches on lessons 6 and 9, along with providing interesting information about kefir.

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