dies there.5 5. Pickling: In this process, it helps to remove the moisture from the food making the environment unfit for microorganisms to grow. Chemical pickling and fermentation pickling are the types of it. EDTA is added in commercial pickles to increase its life span [90].
6 6. Sugar: It is also a natural preservative which can be found in everyone’s kitchen as the major role of it is to act as a sweetener. Sugar also helps to prevent the spoilage by the help of the process osmosis in which it dehydrates the microbes and bacteria, and yeast cannot breed and reproduce there [89].
7 7. Lye: It helps to convert the food alkaline and helps to prevent the bacterial growth on it.
8 8. Canning: It is the process in which food is being sealed in cans and sterile bottles. Boiling is done in order to make sure that the bacteria is killed, and then, it is being sealed. When the seal is broken, then the chances of food spoilage increases again.
1.8 Antioxidants
Antioxidants usage in the field of food preservatives to save food from degradation has proved to be very effective. The oxidation of food is responsible by the two factors: oxygen and sunlight; so, the preservation procedure involves keeping food away from the contact of air and sun, keeping food in the dark and sealed container or maybe when required sealing it with the help of wax and cucumber where there is no chance for the food to get close or comes in the contact with the sunlight or oxygen but it does have one advantage as oxygen is the primary source for the respiration of plants so the plant products present there smells really bad and also the color of the products sometimes change. In addition, 8% oxygen is contained in the packaging of fresh fruits and vegetables. Antioxidants play an important part as preservatives, It helps to prevent the spoilage by fungi and bacteria [88].
Unsaturated fats are the most widely recognized atoms attacked by the process “oxidation” that makes them rancid. Oxidized lipids are regularly stained and result in displeasing tastes, for example, metallic or sulfurous flavors. It is essential to keep away the food from oxidation. These kinds of food are hardly preserved with the help of drying, and they are usually preserved with the help of salting/pickling, smoking, and fermenting. Before air drying the fruits which are less fatty foods are sprayed with antioxidants (sulfurous). Metals act as a catalysis in the process of oxidation, so it is better if fat oils like butter should not be kept in the Al foil or in any other metal container. Olive oil are halfway shielded from oxidation by their inherent antioxidant property but rest is sensitive toward photooxidation. Antioxidant additives are additionally added to fat based beautifying agents, for example, lipstick and lotions to forestall rancidity.
1.9 Oils and Spices
These are used as preservatives in pickles. Oil makes a protective covering and prevents contact of microorganisms and air with the food. Spices do not have bactericidal effect in concentrations usually used. Cinnamon and cloves containing cinnamic anhydride and eugenol, respectively, are more bacteriostatic than other spices. Extracts of garlic onion cabbage are inhibitory to Bacillus subtilis and E. coli [92].
The essential oils are the liquids that are extracted from the plant materials (such as fruits, flowers, barks, and peel), which are aromatic and volatile in nature. There are many uses of essential oils such as in medicine, perfumes, cosmetics, and as food spice and preservative. The initial use of essential oil was in medicine in the 19th century then they were used as odor and flavor ingredients and their business and usage increased in this field and became the priority. Out of 3,000 essential oils which are known yet, 300 out of them are used in the fragrances and flavor industry.
Essential oils has antimicrobial properties so they are regarded as secondary metabolites and they are essential for flora defense. Secondary metabolites “antimicrobial” property was tested by using vapors of essential oils by De la in 1881. From then, essential oils have been proved as the greatest examples that shows this property [94], and not only antimicrobial but also insecticidal, antiparasitic and antioxidant properties too. They act as the builders for the growth of animals.
In spite of the fact that the food business utilizes essential oils as flavoring agents, they also proved to be as the major source of antimicrobials in the process of food preservation. But, one should have all the knowledge about the properties of essential oils, i.e., the MIC (minimum inhibitory concentration), the mode of action, the range of target organisms, and the impact of food matrix components on their antimicrobial properties.
The diversity of compounds is created by plants containing antimicrobial activity. Some are constantly present while others are delivered because of the physical injury or microbial invasion. Essential oils are the blend of at least 45 various components so recognizing the most active component is not an easy task. There are various methods to extract the oil by mixing few components. Essential oils is widely spread family of organic compounds having low molecular weight with having huge contrasts in the antimicrobial activity [96]. There are four divisions in the active compounds as indicated by their chemical structures which are terpenoids, terpenes, phenylpropenes, and others.
1.10 Introduction to Hurdle Technology
Hurdle technology is a technique to control and eliminate pathogens by combining two or more factors. These factors are called hurdles. The pathogens have to overcome these hurdles to survive the right combination of the hurdles inactivates the pathogens and thereby makes the food product safe for consumption along with an extent shelf life [91, 93].
Hurdle technology is the technology where appropriate types of hurdles are selected and combined to provide microbial safety, stability, sensory, nutritional value, and economic viability to products.
The concept of combining several factors is known as hurdle effect. Food preservation can be attained by different types of hurdles. The different types of hurdles used for preservation are classified into three types.
1 1. Physical
2 2. Physicochemical
3 3. Microbial hurdles
These hurdles also influence the quality and safety of foods depending on the intensity of different types of hurdles used, and their effect on food quality may be either positive or negative. The main objective of the hurdles is to eliminate and inactivate or inhibit the growth of microorganisms present in food. Common salt used as hurdles to control the microbial load in foods [95]. Natural antimicrobials also called as bio preservatives like nisin, bacteriocins, and essential oils can also be used as one of the hurdles.
1.10.1 Advantages of Food Additives and Preservatives
Nowadays, food preservatives play an important role in our daily routine food. They give us safety from the bacteria and microorganisms that can damage the food as well as our health. We cannot take preservatives as for granted as they also play useful function in food. They improve the nutritional value of some food weakening unhealthy things from it and improving the quality of the product. Preservatives are play important role by increasing the life of a food and prevent from spoilage. Even though additives and preservatives are necessary for maintaining food safety, they are also danger for health [97–100]. The reasons of adding additives in food are as follows:
i) For maintaining consistency: by emulsifier, stabilizers and thickeners give food a good texture and prevent them from separating.
ii) For maintain quality: as they improve food texture, flavors, appearance, enrich in nutritional value, and maintain food consistency.
iii) For maintaining
