News & Events

5 Reasons Why Canned Food Can Be Quality Food

Author: Carolyn Loong (Lecturer, UCSI University)

Principle of canning:

Canning is a food preservation method where food that has been cleaned and properly prepared is filled into a container and hermetically sealed (airtight). The container is then heated to a set temperature and time to kill food spoilage microorganismsand any pathogens that cause foodborne illness.The airtight seal is necessary to prevent re- contamination of the product after it is heat sterilized.Canned foods that are properly processed can be kept for an indefinite period of time. With this methodof preservation, chemical preservatives are not needed in the food canning process. Metal cans, glass jars, flexible pouches and rigid trays are the major types of containers used for canning purposes.

A walk along the aisle of supermarkets will show many products with colourful, attractive labels bearing words such as "Premium quality", "100% quality", "Committed to quality" and yet sometimes it leaves a consumer wondering what do these promises hold? What is the definition of "Quality"?

Quality gurus such as Crosby defines it as "Conformance to requirements", whilst Juran defines it as "fitness for use".1 Yet some others defined it just as "Wow" or "Quality is never having to say you are sorry" or "When the customer returns and the product doesn’t". 2

The definitions have similar undertones implying the excellence of the product. The commonly accepted definition of quality is "the conformance to requirements or specifications"3. In the business world, the requirements, criteria or specifications are now defined by the customer. When the requirements are met, there will be satisfied and repeat customers.

When it comes to food quality, consumers and buyers are fast becoming demanding of what they want in a food product. The overall judgement of food quality is influenced by how people perceive the product through observation of sensory attributes for e.g., appearance, taste, texture and communication about non-observable attributes (health, safety etc). Some of the food quality attributes expected by today’s consumers can be summarised into areas related to the aspects of sensory, safety, health, shelf-life, and convenience. The other extrinsic factors influencing the consumers’ acceptance of a product are other issues such the assigned quality by marketing and the company’s production characteristics (e.g., organic, brand name).4

It is commonly viewed among consumers that canned foods are of inferior quality when compared to fresh foods. However, with good manufacturing practices, can canned foods help meet the demands of today’s busy consumers; fulfilling the quality attributes sought in a food product? Let us therefore, take a brief look at what canned foods can offer to consumers based on the 5 aspects of quality attributes below.

 

Food Quality Attributes:

  • Sensory characteristics in food
  • Food Safety
  • Nutritional value and health promoting functions
  • Shelf-life of food
  • Convenience

 

Sensory aspects:
Canning preserves the sensory attributes such as appearance, flavour and texture of fresh foods to a large extent. Microorganisms and enzymes in fresh foods which cause undesirable sensory changes in foods are inactivated during the canning process. For example, browning due to oxidation of phenolic compounds and softening of plant tissues due to the presence of enzymes such as phenolase and pectinase, in fresh fruits and vegetables can be arrested by heat processing. Flavour changes resulting from lipase and proteolytic activity can also be slowed down.5 Due to the absence of oxygen in the can, the colours and flavours of canned food can remain relatively stable during the storage period up until the time they are consumed.

Canning can help in improving palatability and organoleptic quality of food produce by causing desirable changes in food. Food becomes more tender and pliable with the desired cooked flavour and taste. Hard and tough foods such as dried peas and beans, shelled abalone,bamboo shoots, etc. are softened, offering time-reduction during cooking of meals requiring these ingredients. Canning of fruits in syrups retains the colour, flavor and texture of the fresh produce. Tomato is another example of a vegetable where it is better canned as they are more flavourful than fresh tomatoes6.

During the canning process, responsible food processors take every effort to ensure optimal processing conditions to achieve optimum quality in canned foods. The quality control of raw materials, preparation, packaging and processing parameters are carefully monitored to ensure the production of canned products with acceptable sensory quality characteristics. For fruits and vegetables, appropriate varieties are selected for canning as they must be able to withstand the heat treatment without undue softening or disintegration.5 Quality optimisation during thermal processing involves optimum balance between inactivation of spoilage microorganisms and retention of quality parameters. Methods such as the use of agitating retorts and pH adjustment of food to reduce the process severity are some of the measures taken to ensure optimal quality in the canned products.7 Effort is also made to ensure a standard colour in the product by sorting off-coloured raw materials as variation affects the quality of the canned product3.

Food Safety aspects:
Canning is a safe method for preserving food. It involves hermetic sealing of food in a container and then heating it to destroy food spoilage microorganisms and food pathogens. The air tight seal prevents re-contamination of food by harmful microorganisms. The minimum temperatures and timing for safe processing for various foods are established by scientific methods. As a result, canned foods are commercially sterile and have a shelf life of at least 6 months at room temperature.8 Food poisoning cases related to commercially canned foods are rare, and the majority of cases are linked to home-canning. In US, the food canning industry has a good track record as to date, only 3 food poisoning outbreaks from commercially canned foods were reported since 1925. It has been said that the likelihood of getting serious foodborne illness from canned products is probably less than 1 in 100 billion.9

Canned products do not need to rely on the addition of chemical preservatives to destroy spoilage microorganisms for shelf-life extension. This comes as a relief for consumers concerned with any allergy or toxicity linked to this group of food additives. Food metal cans are usually made of mild steel rolled into a thin strip that is electroplated with a thin coating of tin on both sides. They can withstand high temperature processing, are impermeable to light, moisture, odours and microorganisms and therefore, provide total protection to the contents. In addition, they are tamper proof. The tin may be coated with a layer of lacquer on the inside of the can to prevent corrosion and other spoilage problems due to interactions with food. A variety of lacquers with different properties and functions have been developed for tin cans for different food groups. For e.g., epoxy-phenolic compounds which are resistant to acids, have good heat resistance and flexibility, are widely used for canned meat, fish, fruits pasta and vegetable products.5 In recent years, there were some apprehensions relating to Bisphenol A (BPA), a key ingredient in the resins, being leached out during heat processing and posing a potential health hazard to children, infants and foetuses. However, in 2012, the Canadian government has reaffirmed the safety of Bisphenol A (BPA) in all food contact applications. Health Canada has stated that BPA use in food packaging poses no health risk to infants, children or adults.10US Food and Drug Administration’s current assessment is also that BPA is safe at the very low levels that occur in some foods.11 Concerns about lead leaching into metal canned foods can also be eliminated now as most three-piece cans used for food canning are manufactured by welding rather than lead soldering of the side seams. The welding process uses electrodes that apply pressure and electric current to overlapping edges at the side seam.5

Throughout the many operations involved in the processing of canned foods, strict monitoring of all these processes are taken to ensure canned food safety. An important management method, Hazard Analysis Critical Control Point (HACCP) system, is commonly adopted to ensure the safety of canned foods. It is a food control system based on the prevention of safety problems by identification, assessment and control of hazards during the various stages of processing product. Factors such as effective heat penetration into the product, minimisation of contamination prior to sealing and a tight seal are carefully controlled.5 In addition to the elimination of microbiological hazards, other safety issues taken into considerations are the absence of chemical hazards such as pesticides, herbicides, natural toxins and cleaning liquids. Steps will be taken to ensure that these do not end up in the finished product. Physical hazards in the form of wood, sting, dirt, etc. will be also controlled and prevented from entering the food system at unacceptable levels4. ISO 22000, a food safety management system which contains the elements of HACCP and Good Manufacturing Practices (GMP) is also widely implemented among food canneries.

In Malaysia, food canners must comply with the standards and regulations for food safety activities. The legislative documents that have an impact on food safety are the Food Act 1983, Food regulations 1985, Pesticides Act 1974, Fisheries Act 1983, Veterinary Surgeon Act 1974, Animal Ordinance 1953 and the Trade Description Act. The Food Regulations 1985 contains the definitions and standards for various food items, stipulate the permitted food additives and nutrient supplements; specify their permissible limits; covers packages and containers for food, requirements for food labelling as well as list the tolerable levels of chemical residues.12 This will ensure that consumers are protected from health hazards and fraud in the preparation and sale of food.

With the cooperation of retailers and consumers such as an efficient rotation system of first in, first out of stock, careful handling and proper storage in cool, dry place to protect the integrity of the cans and hermetic seal; as well as washing of cans before opening them to avoid contamination of contents, commercial canned foods can be considered a safe food.

Health aspects:

Health properties of a food product are that which are necessary for body functioning and contributes to a person’s wellbeing. The nutritional value, presence of health improving agents and satiation characteristics of the food product are major determinants of the health properties of a food.4

Whilst canning may cause some losses in nutritional value of the food due to the heat processing, canned foods remain good sources of nutrients. Canning of fruits and vegetables can help preserve nutrients which otherwise would be lost during storage and decay of fresh fruits. As most produce are processed soon after harvesting, it is able to seal in the nutrients at its maximum value. Since it is packed under vacuum and protected from deterioration factors such as oxygen and light, the food remains fairly stable until consumed13. Studies have shown that canned foods are nutritionally comparable and in some cases, higher than their fresh or frozen varieties.13, 14,15 For example, canned pumpkin were tested have more vitamin A, canned tomatoes have higher levels of vitamin E and lycopene and canned beetroot and cherries higher total phenolic compounds when compared to their fresh counterparts.14,15 The thermal process appears to have increased the extractability of nutrients from the cellular matrix resulting in higher levels, in canned foods. In addition, the canning process concentrates the vegetable increasing the nutrient values in the same amount of food15,6 Lycopene, an antioxidant which may have anti-cancer properties, was found to have higher bioavailability after it is heated or canned.14 Other nutrients such as folate which is an essential vitamin, soluble, insoluble and total fibres in fruits and vegetables did not change significantly after canning. In some cases, fibre becomes more soluble and useful for the body.14,15

Since heat does not reduce protein content, canned meats and poultry are comparable in nutritional value to the fresh cooked foods and are therefore, convenient alternatives as it reduces preparation time. Sterilised soya – meat products may show an increase in nutritional value as trypsin inhibitor in soy beans will be denatured as a result of the heat processing. Canned fish can provide additional calcium as the fish bones are sufficiently softened for them to be consumed.15 Studies have also shown that minerals such as calcium and potassium are retained in the food during the heat processing. Furthermore, canned products may have higher levels of calcium and other minerals due to the uptake of hard water used in the processing as well as the addition of calcium salts to minimise softening in canned vegetables14

During storage, minimal degradation of nutrients occurs due to the lack of oxygen in the can. Fresh fruits and vegetables tend to lose nutrients more rapidly than canned products due to destruction by light or exposure to air.16 Besides that, due to the wide application of the canning process, many functional foods with health improving agents (such as food with omega-3 fatty acids, antioxidants) and good satiation characteristics (high in protein, high in resistant starches, etc.) can be formulated and processed into canned foods, providing diversity to the types of canned food available.

Shelf-life aspects:
Shelf-life is defined as the time during which the product will remain safe, keep desired sensory, chemical, physiological and microbiological characteristics, and comply with any label declaration of nutritional data4.

As canning is a high-heat process that renders the food commercially sterile, properly seamed canned foods have an almost indefinite shelf-life at moderate storage temperatures of 24oC and below. An article reported that 100- year- old canned foods such as brandied peaches, oysters, plum tomatoes and mixed vegetables were found in the sunken steamboat Bertrand in Nebraska. Analysis conducted by a group of scientists showed that although the food had lost its fresh smell and appearance, no microbial growth was detected and the food were safe for consumption. Significant amounts of vitamins A and C were lost, but the protein levels in the food remained high and all the calcium values were comparable to current day products. In another case, a 40-year-old can of corn found in the basement of a home in USA looked and smelled like recently canned corn. Tests showed that the canning process had kept the corn safe from contaminants and much nutrient loss.16

As a general rule, depending on the commodity, canned foods have a shelf life of at least two years from the date of processing. However, it is expected that canned foods can retain its safety and nutritional value beyond two years but may have variations in quality due to changes in colour and texture upon prolonged storage.17

Convenience and Cost aspects:
There are countless canned food products ranging from canned cooking sauces, canned desserts, canned fish/seafood, canned fruits, canned meat, canned pasta, canned soups, canned vegetables to more exotic varieties like canned escargot in the market. This makes easy access to a wide variety of fruits, vegetables, legumes and meats all year long regardless of the season and country of origin. As fresh produce varies in cost depending on the season, purchasing canned foods may be more economical during a certain time of the year. Other than the variety and abundance of flavour, there is the added benefit of convenience. Supplies are easily available in supermarkets. They can be stocked up for use at home anytime of the week or even year with the bonus that it does not need refrigeration. As canned foods are already cooked, they do not require further cooking but reheating only. In addition, they can be quickly and easily added into recipes, allowing creativity in food preparation and saving preparation and cooking time and energy.

A survey comparing the cost of obtaining key nutrients (including protein, fibre, potassium, vitamin A, vitamin C, and folate) from canned, cooked, frozen and dried varieties of common foods showed that canned foods almost always offered an affordable and convenient way to get the needed nutrients. As a case in point, results showed that it cost 65% more to obtain dietary fibre from fresh tomatoes than from the same portion of canned tomatoes. Canned corn offers the same amount of dietary fibre as fresh corn at 25% cost savings, when taking into consideration the waste associated with fresh corn and the time needed to prepare the food.17Another benefit is that canned foods have longer shelf-life than fresh food so, money is not wasted due to food spoilage. 18

In summary, it is evident that canned foods have the potential to fulfil the 5 quality attributes sought in food. However, careful quality control and assurance throughout the food chain is necessary to ensure the right product is made at the right time at the right cost, making it a quality product.

References:
1. Puri, S.C. (1992). ISO 9000 Certification and Total Quality Management. UK: Standards-Quality Management Group.

2. Quality Digest. [Online] Available from:
http://www.qualitydigest.com/magazine/2001/nov/article/definition-quality.html/ [Accessed on 28th July 2013]

3. Gould, W.A. and Gould, R.W. (2001). Total quality assurance for the food industries. 3rd edition. USA: CTI Publications Inc.

4. Luning, P.A. and Marcelis,W.J. (2009). Food Quality Management.Technological and managerial principles and practices. The Netherlands: Wageningan Academic Publishers.

5. Brennan, J.G. (2006). Food processing Handbook. Germany:Wiley-VCH.

6. Schaeffer, J. (2009). Today’s Dietitian. Canned Foods Make a Comeback. [Online] March Vol. 11 No.3 pg.44. Available from: http://www.todaysdietitian.com/newarchives/td_030909p44.shtml [ Accessed on 28th July 2013]

7. Awuah, G.B., Ramaswamy, H.S., Economides, A. (2007). Thermal processing and quality: Principles and overview. Chemical Engineering and Processing Vol.46 pg. 584-602

8. Fellows, P.J. (2000). Food Processing Technology.Principles and Practice.2nd edition. UK: Woodhead Publishing Ltd.

9. Institute of Medicine (US) Food Forum (2009).Managing Food Safety Practices from Farm to Table: Workshop Summary. Chapter 2, Recent Outbreaks in Food Products: Lessons Learned from Past Experience. Washington (DC): National Academies Press (US).[Online] Available from: http://www.ncbi.nlm.nih.gov/books/NBK26429 [Accessed on 10 Aug 2013]

10. Health Canada (2010). Bisphenol-A.[Online] Available from :http://www.hc-sc.gc.ca/fn-an/securit/packag-emball/bpa/index-eng.php. [ Accessed on 28th July 2013]

11. U.S.A. Food and Drug Administration (2013) Bisphenol A (BPA): Use in Food Contact Application [Online] Available from : http://www.fda.gov/NewsEvents/PublicHealthFocus/ucm064437.htm[Accessed on 28th July 2013]

12. FoodAct 1983 (Act 281) & Regulations (2010). Malaysia: International Law Book Services.

13. Rickman, J., Barrett, D. and Bruhn, C.(2007). Nutritional comparison of fresh, frozen and canned fruits and vegetables.Part 1.Vitamin C and B and phenolic compounds.Journal of the Science of Food and Agriculture. Vol. 87 (6) p. 930-944.

14. Rickman, J., Barrett, D. and Bruhn, C. (2007) Nutritional comparison of fresh, frozen and canned fruits and vegetables II. Vitamin A and carotenoids, vitamin E, minerals and fibre.Journal of the Science of Food and Agriculture.Vol. 87 (7) p.1185-1196.

15. Klein, B. and Kaletz, R.(1997) Nutrient conservation in canned, frozen, and fresh foods. University of Illinois.

16. Blumenthal, D. (2007) FDA Consumer. The Canning Process: Old Preservation Technique Goes Modern [Online] Available from: http://web.archive.org/web/20070509153848/http://www.fda.gov/bbs/topics/CONSUMER/CON00043.html. [Accessed 28th July 2013]

17. Kapica, C, Weiss, W. (2012). Canned Fruits, Vegetables, Beans and Fish Provide Nutrients at a Lower Cost Compared to Fresh, Frozen or Dried. Journal of Nutrition Food Science. Vol 2 (131).

18 Threadaway, A. (2011) Alabama Cooperation Extension System Canned Goods Shelf-life. [Online] Available from: http://www.aces.edu/counties/StClair/documents/NRCannedGoodsShelfLifeTreadaway2011.pdf. [Accessed on 27th July 2013]