Code and Title of the Paper: F01FP Food Preservation Code and Title of the Module: F03FP16 Curing and pickling of foods Name of the Content Writer: Ms. A. Sangamithra Curing and pickling of foods Quadrant - I Introduction Food preservation is as oldest as mankind. Our ancestors used natural techniques to preserve their foods for a long lasting shelf life. They used frozen climates to freeze the meat and dried the products during sun in tropical areas. Curing and Pickling was one such preservation technique exists from the ancient days. Both the techniques use the addition of salt or brine to the product to suppress the growth of microbes. Curing was used to preserve meat for a longer duration, when the refrigeration facilities were not available. Both curing and pickling process extends the shelf life and also improves the flavor and taste of the food products. Objectives On completion of this session you will be able to 1. Interpret the principles of curing and pickling and its effect on growth of microorganisms 2. Identify the different types of curing and pickling of foods. 16.1 Curing Curing is a preservation method usually done for meat and fish.It is carried out by the addition of combination of salt, nitrite and/or nitrate salt, sugar.Curing is an appropriate method to prevent the microbial growth, preserve the original flavors of the meat,increase the water retention and fat binding properties, and also to keep essential minerals and vitamins. The curing is further continued by other specific processes such as fermentation, drying and ripening of meat. The length of curing process depends on the type of meat cut,size of the meat pieces and composition. The whole process can last up to three to six months. For few specialty ham products, the process may go up to 24 months. 16.2Science behind curing Sodium chloride (common salt) or sodium nitrate or combination of these salts can be used for curing of meat or fish products. The addition of salt does not destroy the bacteria, but it prevents or slows down their growth by creating an unfavorable conditions. Instead of inhibiting the growth of all organisms, it allows for a moderate amount for fermentation to occur. The fermentation ends up with a creation of distinct flavor to the meat. The curing salt makes the meat or fish tender by break down of protein in muscle fibers. Finally, salt also act as a dehydrating agent, which removes water from the meat by diffusion. Hence the final product will contain less water and more salt. Thus the salt creates an environment which is detrimental to the microorganisms. 16.3 Curing Ingredients The most commonly used curing ingredients are salt (sodium chloride), sugar, nitrite and/or nitrate and phosphates. Each ingredient has it unique characteristics and also plays an exclusive role in preservation. 16.3.1 Sodium chloride Code and Title of the Paper: F01FP Food Preservation Code and Title of the Module: F03FP16 Curing and pickling of foods Name of the Content Writer: Ms. A. Sangamithra Sodium chloride or common salt is the basic ingredient in all curing methods. Salt serves as a preservative agent and flavoring agent to the cured products. It has the capability to bind water and withdraw mositure from meat. When meat is exposed to brine or salt, the free moisture is attracted towards the sodium chloride ions and reduces the water activity. Reduced water activity creates an unfavorable condition for the growth of microorganisms. The water holding capacity of meat is increased with addition of 5 % of salt in meat. This 5% of salt inhibits the growth of anaerobic bacteria whereas 10% salt inhibits almost the growth of most bacteria except few salt-tolerant species. The addition of salt also improves the flavor of cured meat. Based on the consumer acceptability in cured hams, the optimized salt concentration is found to be 2.5%. 16.3.2 Nitrate/Nitrite Nitrates and nitrites are added during curing in the form of potassium or sodium nitrates and nitrites. They are toxic when used in large amounts. Hence it is mandatory to use the exact amount of the above curing agent. The major functions of nitrate/nitrites is to stabilize color in cured meats, to impart characteristic flavor to meat, to retard rancidity in meat by stabilizing the fat and to inhibit many pathogenic organisms especially Clostridium botulinum. Sodium nitrate does not directly involve in curing, it get converted into nitrite which is responsible for the further reactions. The bacteria present in meat react with nitrate to form nitrite. Sodium nitrite has the ability to react with the red meat pigment to form the heat stable red curing color. A mixture of 99.5% salt and 0.5 % sodium nitrite is available to reduce the risk of overdosing. This homogenous mixture is called as curing nitrite salt. Nitrogen oxide is formed when nitrite is exposed to acidic environment. This nitrogen oxide combines with myoglobin to form nitrosomyoglobin which is a heat stable, bright red compound. A 2% of nitrite in curing salt generates approximately 150ppm (150 mg/kg) nitrite in meat products. On further reaction with myoglobin, the cured meat product will contain 50-100ppm of residual nitrite. This residual nitrite in cured meat should not be exceeding 125ppm. 16.3.3 Sugar Sugar or corn syrup can also be added during the curing to reduce the harshness of salt and excess moisture removal. This process is also called as sweet pickling. The sugars most frequently used are sucrose, cane sugar, dextrose, and invert sugar. Addition of sugar also imparts flavor to the cured meat by serving as a food by flavor producing bacteria. The presence of sugar in the cured meat imparts browning during smoking and a characteristic flavor during cooking. Sugar prevents the oxidation of meat pigments by blocking the formation of unwanted derivatives during curing process. It also improves the color of meat pigment. It provides food for the desirable microorganisms which produce acid and favor for the production of necessary meat pigments. 16.3.4 Phosphates The addition of phosphates during wet curing of meat tends to double the water binding capacity of meat products. It results in the increase in pH which increases the capacity of the muscles to Code and Title of the Paper: F01FP Food Preservation Code and Title of the Module: F03FP16 Curing and pickling of foods Name of the Content Writer: Ms. A. Sangamithra bind water. The increased pH causes unfolding of the muscle proteins, thereby making more sites on the proteins available to bind water. Sodium tripolyphosphate, sodium hexametaphosphate and sodium pyrophosphate are approved by USDA for use in meat curing. 16.4 Curing Accelerators The duration of curing can be shortened by the addition of curing accelerators. The usage of reducing compounds (reductants) and acidulants are important for the development of color and other meat properties. Ascorbic acid, sodium ascorbate, erythorbic acid and its derivatives are the reductants widely used for meat curing. The major role of curing accelerators is to speed up the chemical conversion of nitrite to nitrosomyoglobin to obtain the stable meat pigment. These accelerators are added along with the curing salt. Sometimes, the curing agents are coupled with acidulants such as fumaric acid and glucano-delta-lactone for rapid conversion of nitrate to nitrite. The reductants such as ascorbic acid or vitamin C, and isoascorbic or erythorbic acid possesses antioxidant properties. Sodium ascorbate and sodium erythorbate are sodium salts of the acid are commonly used in meat curing. They are effective in reducing metmyoglobin to myoglobin and accelerate the production of nitric oxide from nitrite. They are highly effective in maintaining the fresh meat color. The ascorbic acid or erythorbic acid is added in cured meat or poultry at a maximum concentration of 469 ppm. The acidulants provide an acidic environment which encourages faster conversion of nitrite to nitric oxide. Reduced pH will accelerate the curing process but also reduces the water binding capacity of the meat which in turn reduces the yields. A maximum concentration of only 0.5% is permitted to add in the meat. 16.5 Methods of Curing There are three methods of curing. They are dry curing,wet curing and injection curing. 16.5.1 Dry curing Dry curing is also referred as dry salting or corning. The term ‘corning’ comes from the word ‘corn’ which means grains of salt. It is the process of applying dry salt along with sodium nitrate(99.5% common salt or sodium chloride and 0.5% sodium nitrite). The whole meat pieces or meat cuts are rubbed with the salt and stacked on each other with layers of curing salt. The salted meat cuts are stored at low temperature (0 to +4°C). The product is completely covered to protect from the air. During this process, the salt diffuses through the meat tissues and the liquid from meat oozes out. The extracted liquid from the salted meat is collected separately from the bottom of the stacks. Dry curing mix can be sprinkled over the piled products. For uniform curing, rearranging of the lower pieces to the upper stack and vice versa should be done. Dry curing is especially carried out sausages, hams and bacon. These dry cured products will be further smoked and air dried, which does not need additional cooking. 16.5.2 Wet Curing The wet curing method otherwise called pickling or immersion curing. This process involves the immersion of meat in the brine solution. The brining solution contains water, salt and optional spices or herbs.