Course:FNH200/Projects/2021/Canned Soups

Canned Soups Preliminary Questions and Research

Preliminary Questions:

• What preservatives are used in the soup?
• Do any of the preservatives double as flavour enhancers?
• Why must canned soups be so high in sodium?
• Do any of the preservatives affect the nutritional value of the main ingredients of the soup?
• Is the addition of monosodium glutamate (msg) harmful to health?
• What is the canning process of Campbell’s Chicken Noodle Soup?
• Are canned soups less nutrient dense than a fresh soup? Are vitamins destroyed through canning?

Potential Sources:

• https://www.jrnjournal.org/action/showPdf?pii=S1051-2276%2818%2930109-2
  • Title: Waiter, There’s Potassium in My Soup!
  • Addresses potassium and sodium contents of canned soups
• https://link.springer.com/content/pdf/10.1007%2F978-3-030-46814-9_16.pdf
  • Title: Food Preservation
  • Explains food preservation
• https://meridian.allenpress.com/jfp/article/63/11/1503/169725/Bacterial-Spore-Inhibition-and-Inactivation-in
  • Title: Bacterial Spore Inhibition and Inactivation in Foods by Pressure, Chemical Preservatives, and Mild Heat
• https://gs.alexu.edu.eg/new/upload/Students/0907/0907(2)705_2019-2020_Spring/0907-3-010_assignment_1.pdf
  • Title: Uses, effects and properties of monosodium glutamate (MSG) on food & nutrition
  • Talks in depth about MSG and its effect on taste and how it is metabolized
• https://springer.com/article/10.1023/B:QUAL.0000040350.91485.30
  • Title: Effect of storage time and preservatives on vitamins and pigment contents of canned tomato soup

Introduction

One of the most popular inventions that resulted from the creation of canning are commercial canned soups. Canned soups can be “ready-to-eat” (no water needs to be added) or condensed (prepared by adding water). Condensed soup was invented in 1897 by Dr. John T. Dorrance, who was a chemist at Campbell’s Soup Company. The three most popular Campbell’s soups in America are Tomato, Cream of Mushroom, and Chicken Noodle. These three soups alone make up 2.5 billion bowls of soup consumed by Americans every year.

While commercial canned soup has become a multibillion-dollar industry due to its convenience, affordability, and tastiness, there has been rising concern about its effect on human health due to its high sodium content, the addition of certain preservatives, and the possible exposure to BPA (bisphenol A). Here, we will explain the general canning process of commercial canned soups. We will also investigate the nutritional value of canned soups, as well as the use of salt and preservatives, including MSG, in canned soups.

Campbell's Chicken Noodle Soup

Common Ingredients Used in Canned Soups

Ingredients (Using Campbell’s Chicken Noodle Soup as an example)

• Chicken broth (water, chicken stock)
• Noodles (wheat flour, whole egg)
• Season chicken (soy)
• Salt
• Chicken fat
• Monosodium glutamate
• Corn starch
• Flavour
• Onion powder
• Yeast extract
• Spice extracts
• Beta carotene
• Dehydrated garlic

Common Preservatives Used in Canned Soups

• Monosodium glutamate (MSG)
• Potassium sorbate
• Sodium phosphate
• Lactic acid

Canning Process of Commercial Canned Soups

The manufacturing design of canned soup has four main stages: ingredient inspection and preparation, blending, filling, and processing.

Step 1: Cleaning, preparation, and inspection

First, the vegetables are steam cleaned and peeled. After peeling, the vegetables are diced.

The stock of the soup is also prepared often from bones and meat which are simmered in water in stainless steel tanks with steam-heating. The ingredients used in the manufacturing of canned soup are regularly tested to examine their microbial loads when they enter the commercial canned soup factory. The microorganisms of interest are the spores of mesophilic and thermophilic bacterial spore formers.

Step 2: Blanching

The diced vegetables are then sent to the blanchers. Blanching of the vegetables inactivates their enzymes to prevent the enzymatic degradation that happens between packaging and thermal processing. As the blanching procedure occurs at around 95 °C, it also pre-cooks the vegetables, cutting down the time it takes to cook the soup later on.

Step 3: Blending (mixing)

Then, the ingredients are combined into the soup according to exact formulas and procedures set by the soup manufacturer. During blending, a traditional steam kettle is often used where ingredients are dumped from barrels or pumped in. Steam pipes around the exterior of the barrels heat the ingredients. Recent technology has created a radically different device called the ribbon blender, which has rotating blades that go and forth allowing the ingredients to be blended at a lower temperature. This new technology reduces cycle time and improves product quality.

Step 4: Filling

When blending of all the ingredients is complete, the filling process deposits soup into cans. The temperature during this step of soup manufacturing is 60-85 °C. The cans are made from steel and then coated with a thin layer of tin to prevent rusting. In the past, BPA (bisphenol A) has been used to line the steel cans to preserve the soup’s taste. However, consumers are worried about the exposure to BPA as it is associated with negative health effects (e.g. increased blood pressure, type 2 diabetes, and cardiovascular disease). Recently, various commercial soup manufacturers, including Campbell’s, have transitioned from using BPA linings to using acrylic or polyester materials in the lining to separate the soup from the metal.

Step 5: Sealing

After filling the cans with soup, the cans are sealed.

Step 6: Sterilization (cooking)

As various types of soups are in the low acid pH range, they have to be sufficiently sterilized through the process of canning to ensure shelf stability. There are different processes to cook soups commercially. Products like Campbell’s Chicken Noodle Soup are placed inside a rotary cooker, which is a steam shell that cooks the soup. Some other soups can be cooked in a device called the Stork hydrostatic cooker. This device consists of a series of chains that are called “flights” which the soup rests in. The cans of soup go up and down through large towers that are filled with steam to cook the soup. The temperature at which the soup is cooked is typically around 110-130 °C.

Step 7: Cooling

Then, the cans of cooked soup go into a cooling unit which brings the cans down to room temperature before it is labeled.

Step 8: Labeling

Once cooling is complete, the cans are labeled.

Nutritional Value of Canned Soups

The nutrition label of Campbell’s Chicken Noodle soup states that in one 250 ml serving there is 125mg of potassium, 40mg of calcium and 0.75mg of iron. Canning is a heat processing preservation method, it is known to have both positive and negative effects on nutritive value. Heat processing gelatinizes and denatures starches and proteins making them more easily digestible. However many vitamins are sensitive to this process and are destroyed and degraded. Before being canned the vegetables in soup are blanched, blanching is beneficial from a nutritional aspect in that it inactivates enzymes that cause degradation that leads to vitamin losses. Blanching does lead to the loss of water-soluble vitamins such as vitamin C and B-vitamins like biotin, riboflavin and thiamine, due to them leaching into the water the vegetables are blanched in.

Canned foods are readily available and have very long shelf lives, they are more convenient than making fresh soup. A fresh homemade soup would likely have more B-vitamins assuming you do not blanch the vegetables used separately, however vitamin C is very heat sensitive and would likely still not be present. So if a canned soup is the more accessible option, it is perfectly reasonable to choose it as the nutritional quality is very similar to its homemade equivalent.

Salt Content in Canned Soups

Canned soups are usually high in sodium due to various reasons. First, sodium is used as a preservative for food and hence the high levels of sodium are meant to increase the food’s shelf life. As such, the primary reason for using high sodium levels in canned foods is the preservation factor in terms of retaining some level of freshness, appearance and texture of the canned food. While considering Campbell’s Chicken Noodle soup, the canned food contains 800 mg of sodium per 250 ml of serving. Such high sodium levels could render the canned food unsuitable for hypertension patients, as mentioned by Gimbar (e25). The author states that an alternative commonly used to reduce sodium levels in canned foods is potassium chloride (e25). Also, she specifies that the using potassium chloride alternative by some canned food manufacturers is not for preservation purposes but as a “… reduction of calories” (Gimbar e25). In assessing our case study Campbell’s Chicken Noodle Soup, however, there is no mention of any potassium chloride used to reduce the high sodium levels in their product. Secondly, high sodium levels are used in canned foods for flavouring purposes. In this case, sodium is added to canned food to create a salty-like taste hence limiting strange or unwanted tastes that canned food might have. However, one source details that salt, in this case, dietary sodium should be avoided by applying seasoning in soups through various flavourful spices and herbs in place of the salts. In Campbell’s Condensed Chicken Noodle case, sodium is replaceable with different herbs and spices to season the canned food. Conclusively, high sodium levels are used in canned foods, such as the case study, Campbell’s Condensed Chicken Noodle canned food. The sodium is used for purposes of both preserving and flavouring canned foods.  

Preservatives in Canned Soups

The only preservative found in Campbell’s condensed chicken noodle soup is Monosodium Glutamate (MSG). MSG is a naturally occurring sodium salt derived from the amino acid glutamate. MSG doubles as an umami flavour enhancer and is commonly used in Chinese foods, soups, and canned vegetables. Some people can have a negative reaction after the consumption of MSG. Their symptoms include headaches, sweating, and nausea. Research has found no evidence that MSG is unsafe or that MSG causes any of these symptoms. MSG has zero calories, but contains around 130 mg of sodium per gram of MSG. MSG is safe when consumed in small amounts.

Beef stock-based soup use potassium sorbate as a preservative. Sodium phosphate is the preservative used in bean soup. MSG, potassium sorbate, and sodium phosphate are all high in sodium content, which helps to extend the shelf life of canned soup. In dairy-based soups, lactic acid is used as a preservative. This acid helps to prevent the dairy from growing fungus.

Monosodium Glutamate’s Effects on Health

Monosodium glutamate (MSG) is the sodium salt of glutamic acid, a naturally occurring amino acid. It has been commercially manufactured for use as a flavour enhancer since early 1900s. MSG binds to taste receptors in the tongue and enhance taste sensations. It is used to enhance the natural flavour of various foods, such as soups, casseroles, salads, gravies, meat, poultry, seafood, and vegetable dishes. There is enough evidence to suggest that adding MSG to suitable foods increases their palatability, but it does not affect the aroma of a food. MSG can be added or naturally occurring (glutamates) in foods. The human body cannot distinguish between naturally occurring and added glutamates.

MSG (MonoSodium Glutamate)

There are possible toxic effects related to MSG, including CNS disorder, obesity, disruptions in adipose tissue physiology, hepatic damage, and reproductive system malfunctions. However, more evidence of MSG toxicity is still needed.

Studies have shown that glutamate intake may be related with increased risk of overweight irrespective of physical activity and total energy intake. However, long-term animal feeding and human studies have shown that glutamate is not responsible for increasing food intake or inducing obesity. There is no scientific evidence linking obesity in humans with the intake of foods that contain MSG. Several studies suggested that glutamate can be a triggering agent for asthma exacerbations. However, evidence is not consistent in demonstrating that glutamate can trigger an asthmas exacerbation. The consumption of glutamate may also be related to the development of asthmatic bronchospasm, urticaria, angioedema, and rhinitis. Current research has not been successful in demonstrating a perfect and reliable relationship between glutamate intake and the development of these conditions. Glutamate has also been described as a trigger for migraine headache exacerbations, but consistent data is absent, and more clinical research is required identify the relationship between the two. In general, further studies are needed to assess whether the addition of MSG to foods is harmful to health.

There is no regulatory limit to the amount of MSG that may be added to food, but only the smallest amount required to enhance the flavour should be added to the food. The safety of MSG has been studied worldwide. In general, the use of MSG is not a health hazard to consumers, as its safety has been reviewed by regulatory authorities and scientists all over the world, including Health Canada. Some individuals may experience an allergic-type reaction or hypersensitivity to MSG, like burning sensation, facial pressure, headache, nausea, and chest pains. It is recommended that individuals who suffer from these reactions avoid MSG.

Exam Question

Question: What vitamins might be missing from a commercial canned soup product?

A) Vitamin A

B) Vitamin C

C) Vitamin B

D) Two of the above

E) All of the above

Answer: D (Vitamin C and B- vitamins as they are water-soluble and get lost during the blanching process. Vitamin C is also destroyed by heat so its lost doubly.)

This question is important to know because vitamin C and B are essential vitamins. For individuals who eat a lot of canned soup, it would be important to obtain sufficient amounts of these vitamins from other food sources.