What is Food Preservation Methods? Traditional & Modern Methods Of Food Preservation

Author: Sanjana R

ABSTRACT

Food preservation is of paramount importance as it safeguards the safety, quality, and longevity of food items and is a very crucial process in the food processing industry. It involves handling and treatment of the food that will slow down or contain the spoilage of food by killing pathogens and preventing microbial contamination. In addition, food preservation will also preserve nutritional quality, edibility, etc. It will also improve the shelf life of a food product. Thus prevention of food is very important to retain the quality and keep it edible and safe for longer periods of time. The basic aspect and objective of food preservation revolves around food safety, increasing the shelf-life, retaining flavour, texture, colour, etc.  Various food preservative techniques including thermal and non-thermal methods like drying, curing, chilling and freezing, canning, pasteurisation, fermentation, modified atmosphere, vacuum packaging, etc are being briefly discussed in this article.

INTRODUCTION

Food, whether derived from animals or plants, is a fundamental element consumed regularly by everyone. It comprises organic molecules such as carbohydrates, proteins, fats, and moisture. Consequently, food is prone to spoilage caused by microbial, physical, or chemical factors^[1]. Hence, the prevention of food spoilage is crucial to maintain its quality and ensure it remains safe and edible for extended durations. Overall, the objective of food preservation methods is to ensure food safety, prolong shelf life, and retain the flavour, texture, colour, and nutritional value of food products. Different methods are chosen based on the specific characteristics of the food being preserved and the desired outcome. These techniques encompass heat processing, refrigeration, freezing, dehydration, fermentation, pickling, salting, smoking, vacuum packaging, chemical preservation, and modified atmosphere packaging.

Food preservation’s history dates back to many thousand years.  Early man had to preserve the food he hunted.Every culture evolved along with different preservation techniques^[2]. Traditional food preservation techniques like drying, chilling, freezing, pasteurisation and some chemical methods are used regularly in many areas around the world. As technology advances day by day, with scientific expertise, we have modern food preservation techniques like hurdle technology, irradiation ^[3], etc.

FOOD SPOILAGE MECHANISM

Food spoiling is the term used to describe unfavourable alterations brought on by insects, microbes, and enzymes. Food deteriorates when these alterations take place, turning it hazardous or inedible. Food starts to spoil once it’s harvested or caught or killed. Such changes might make the food unsafe for human consumption. Some reasons for food spoilage include, Presence of microorganisms, unhygienic and improper handling of foods, and chemical and enzymatic actions ^[4]. The process by which food becomes less edible is called food spoilage or food deterioration. This is a threat to food safety. Colour, flavour, texture, smell, and food itself can be used to determine the initial phases of food spoilage. various factors contribute to food spoiling like physical, microbiological, or chemical processes. The primary causes of food spoilage include moisture, temperature, pH, air, nutrition, and the presence of various substances like microbial growth and other chemical reactions like browning action, maillard reaction, etc.. The several elements that influence food deterioration are shown in Fig.1 ^[5].

TRADITIONAL METHODS OF FOOD PRESERVATION

CURING

Addition of salt, nitrates, nitrites, sugars in different combinations will lead to dehydration which will kill the bacteria. These molecules bind with water, dehydrating the food; weakening the chances of pathogen survival. Thereby Additionally it will recede the oxidation process thus preventing the food from rancidity. Foods like meat, fish, fruit are cured to reduce the water activity thereby diminishing the microbial attack ^[4]. Addition of salt not only preserves the food, but is also used as a flavouring agent. Many terms like brining, pickling, and salting are used interchangeably.

CANNING

Canning was a preservation technique discovered by nIcholas Appert ^[6]. Canned foods like fruits, vegetables, fish and meat are very popular and most widely found in today’s world. It is one of the thermal food preservation techniques which involves using a sterile can made up of metal, glass or plastic. The basic principle involves heating (sterilising) the food and canning it in an air-tight container. With no access to the external environment, in the void of air, no new pathogen would develop ^[4]. C. botulinum bacteria grows even in the absence of oxygen, which is a threat in canning ^[7].

FREEZING

Freezing is one of the oldest methods used to preserve the nutritional and sensory abilities of the food. When frozen, the metabolic and chemical processes cease ^[9]. Application of cold temperature (below 18°C) ensures keeping the food fresh by arresting the microbial activity. Freezing is applicable to products like ready to eat foods, milk and leafy vegetables ^[8]. Freezing in different temperatures and times is applied for different food products. The disadvantage of this method is that the microbes are only inactivated, not destroyed  ^[4]. So there is a possibility it may come to life once thawed back. Other few limiting factors of freezing are formation of ice crystals, storage instruments and cost. A few other cold preservation techniques involve cooling, refrigeration, cold storage, etc.

SMOKING

Smoking is a technique that is used to cook, impart flavour and preserve the food. It is used in foods like meat and fish. The smoke is introduced by burning woods of different sources. Formaldehyde and phenolic compounds of these smoke have a natural antibacterial and anti-microbial capacity ^[10]. There are two types of smoke, hot smoke used along with frozen foods while cold smoke is used with salted foods. The cautious word to be noted here is WHO reports the risk of carcinogenic properties of smoke inducing cancer ^[6].

FERMENTATION

Fermentation is a very important and widely used preservative technique. Fermentation also improves the flavour, nutrition profile and digestibility of the food ^[11]. This method utilises chemical reactions of the microbes present or added in the food, which will yield beneficial results. Microbes used in the fermentation process produce acid or alcohol which renders harmful effects to the pathogenic microbes; thereby preserving the food product fermented. Food products like bread, wine, beer and dairy products like cheese, yoghourt, some meat, and few more like kimichi, sauerkraut are very popular fermented foods. Controlled elements like temperature, oxygen content, and salt are maintained throughout fermentation to aid the fermentative microorganism in producing a food product fit for human consumption ^[6].

MODERN METHODS OF FOOD PRESERVATION

FREEZE DRYING

Freeze drying is a contemporary method that uses vacuum to extract moisture contents from food at a considerably lower temperature while it’s frozen. The fundamental idea is to do sublimation of solid water (ice) at lower pressure in order to evaporate it ^[12]. In this process, the food is first frozen at –18oC in trays in the lower chamber of the freezer, and the frozen product is dried (first at 30oC for 24 hours, then at 20oC). Low high vacuum (0.1 mmHg) in the upper chamber. Freeze drying technique produces food that is of excellent quality. The food’s form remains unchanged under the circumstances. These foods are hygroscopic, retaining the taste and flavour and can be reconstituted readily. Freeze drying is also a method of dehydrating. Mango pulp, orange juice concentrate, etc. are dehydrated using this method. This method is very beneficial in storing bacteria and yeast ^[13].

VACUUM PACKING

In this method, food is placed in a plastic film bag and a vacuum pump is used to suck air to create a vacuum in the bag before sealing the bag. Under these conditions, microorganisms do not grow because they need oxygen to survive. This technology is mainly used to pack dried fruits, as it keeps them fresh and does not lose their flavour due to oxidation ^[14]. Oxygen is a major contributor to food spoilage as it allows aerobic microorganisms to thrive and promotes oxidation reactions, leading to flavour deterioration and rancidity. By removing oxygen, vacuum packaging helps preserve the quality and freshness of the food for longer periods. Vacuum packaging can help preserve the nutritional content of foods ^[7]; preserving the vitamins and antioxidants present in fruits, vegetables, and other perishable foods.

PASTEURIZATION

Pasteurization is a food preservation technique named after Louis Pasteur, the French microbiologist who developed the process in the 19th century. It involves heating food products to a specific temperature for a predetermined time to destroy harmful microorganisms, such as bacteria, moulds, and yeasts, while minimising the impact on the sensory characteristics and nutritional content of the food. Pasteurisation is commonly used for liquids, particularly milk and fruit juices, to improve their safety and shelf life. In pasteurisation, the food product is heated to a specific temperature, usually between 60°C to 85°C (140°F to 185°F), for a certain period of time. The exact temperature and duration depend on the type of food and the desired level of microbial reduction ^[13]. After heating, the food is rapidly cooled to prevent further microbial growth. This process extends the shelf life of perishable liquids, making them safer to consume and easier to store. Milk, cheese, butter, eggs and fruit juices are some common foods that are pasteurised ^[9].

IRRADIATION

In this method, food products are exposed to ionising radiation such as β- particles or γ- rays. These radiations are efficient in killing bacteria, moulds and pests. These radiations also reduce the ripening of fruits and stop spoilage.This technique has been mostly used for spices, condiments and fresh fruits. Even Though WHO and FAO has certified the use for irradiation, misconception and controversies are going around this method; limiting its usability ^[15].

CHEMICAL FOOD PRESERVATIVES

Chemical preservatives can be of various types such as antimicrobial agents, antioxidants, and chelating agents. Antimicrobial agents inhibit the growth of microorganisms such as bacteria, yeast, and moulds. Antioxidants prevent oxidative reactions that lead to flavour deterioration and rancidity. Chelating agents bind metal ions that catalyse oxidation reactions, helping to preserve colour and flavour. Some commonly used chemical preservatives include sodium benzoate, potassium sorbate, nitrites and nitrates ^[6]. These preservatives are approved for use in food by regulatory authorities and are often added to processed foods, beverages, and canned goods to prevent microbial growth and maintain product quality.

CONCLUSION

Food preservation stands as an indispensable component of food processing, innovation and adaptation. From ancient methods rooted in tradition to modern technologies driven by science, the evolution of food preservation is on a path to overcome the challenges of spoilage and scarcity. Food preservation methods and techniques not only serve as vital tools in ensuring the safety, quality, and longevity of our food supply, but also contribute to food security, public health, and economic stability. As we move forward, there is a growing emphasis on developing sustainable and eco-friendly preservation methods that minimise environmental impact and address the challenges of climate change and resource scarcity. This requires continued research, innovation, and collaboration across sectors to ensure that we can meet the demands of a changing world while preserving the nutritional integrity, flavour, and cultural heritage of our food.

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