Functional foods are the kind of foods that provide health benefits beyond the supply of basic nutrition. The current years have recorded an increasing demand in these foods. Functional foods differ from nation to nation. In the US, functional foods must provide additional health benefits and help reduce disease risks and encourage optimal health. Functional foods in Japan have specific ingredients such that they have effect on the function and structure of the body and regulate specific health conditions. According to the American Dietetic Association (1), in Australia, functional foods should not only reduce chronic disease risks above nutritional functions but also show physiological benefits. Cheese is a dairy food produced from pressed milk curds. It is an ancient food produced throughout the world. Cheese is nutritious, delicious and versatile. It can be eaten by itself or added to other dishes. Cheese has more than 300 varieties (2); some varieties include cheddar, Colby and Mozzarella, which have varied flavors, forms and packages. This report focuses on cheese as a functional food in the country, how it is produced (processing), packaging and innovations in the cheese industry.
According to Glanbia Nutritionals (3), understanding the cheese supply chain from milk pick up from the farms to the final product is crucial in innovation and commercialization. The innovation specialists should have in mind the end product before even starting a new project. Recent research by cheese producing companies show that more cheese is being consumed, with the consumers’ expectations increasing after every purchase (4). In America, an average cheese consumer eats about 15.4 kg per year. A prediction by the Euromonitor International on cheese growth showed that Asia and other Pacific countries would record a growth of 5.5% CAGR through 2020 while Africa and Middle East would record a 5.8% growth. The current generation, aged between 18 and 34, being the leading cheese consumers, are posing a challenge to the cheese producers. The generation is vast in food knowledge and make their choices based on specific considerations. They have, therefore, a big impact on how cheese is produced, flavor assortments, ingredients and way of packaging. This has too advanced cheese innovation.
There are more than 500 cheese varieties. The main ingredient in cheese making is milk (cow, sheep, goat or water buffalo milk). Unlike in most food recipes that use water as an ingredient, cheese making uses it as a facilitator. In the making of mozzarella, water is used to dilute and dissolve citric acid as well as dissolve calcium chloride. Water is also used to make brine, used in the cheese recipe. For the water to be use has to be at a temperature of between 10 to 15 degrees Celsius. Lipase enzyme is naturally found in raw milk and can be removed by homogenization and pasteurization. It has a strong tangy taste when used in high concentration on cheese (5). In Italian cheese, lipase powder is added to milk before rennet and is used in freeing the fragrant fatty acids and giving them a distinct flavor. According to the HomecheeseAdam (6), salt is the third most important ingredient in cheese making after milk, starters and rennet. Salt is used as a preservative, enhancing flavor, as an antibacterial and in the removal of whey from curds (6). This salt has to be non-iodized (cheese salt) otherwise it would destroy the bacteria that generates flavors in the cheese.
Pasteurization and homogenization processes are used to reduce the amount of naturally present calcium in the milk. This calcium results to a firmer curd and its absence would make the curd softer and structurally weaker. Calcium chloride is added to replace the lost calcium. It is added to milk before rennet. Herbs and spices such as pepper and cranberries are used to add flavor to cheese. These herbs and spices have to be clean and dry. Cheese can also be soaked in alcohol before it is wrapped and aged to add flavor. The curds can be steeped in the liquor for a given time before putting it in the mould and pressing or the formed and pressed cheese is soaked in the liquor before it is dried, wrapped and aged. These methods can be used together to further the cheese flavor. Annatto is an orange dye added to the white curds and changes their color to orange. Just like most foods, most cheese ingredients depend on the cheese type desired.
Cheese bacterial culture is known as lactic acid bacterial (7) as the bacterial primary source of energy is the lactose and lactic acid is their primary metabolic product. Starter bacteria used in cheese making include Lactococcus lactis, Lactobacillus delbruckii, streptococcus salivarius and Lactobacillus helveticus. The starter cultures are used in the early stages of cheese making and are help in coagulation by reducing the pH before rennet addition (8). The metabolic activity of the starter cultures help in attaining the required flavor compounds and also prevent growth of pathogens and harmful microorganisms. Adjunct cultures are added to provide and enhance texture and the characteristic flavor of the cheese. They include Lactococcus casei, Lactobacillus plantarum, Brevibacterium linens and Propionibacterium freudenreichii. In some cheese varieties, molds and yeast are used to give the cheese their characteristic flavors and colors.
Different cheese types use different processing temperature, time, processing sequence, salting, aging and pH for different steps. Below is a general process of cheese processing. Milk standardization is the first step. It involves adjusting the milk compositions so as to maximize returns. In the standardization process, the cheese composition and quality specifications must be maintained (9). Standardization is done so as to prove the customers with uniform products, ensure economic production and adhere to the legal requirements for different milk products. Two methods are used to estimate the proportions of various ingredients used cheese making. They are Pearson’s Square method and algebraic equations. For the Pearson’s method, a square is drawn then desired fat percentage placed at the centre and the fat composition of the materials to me mixed placed at the left corners. The number at the center is subtracted from the larger number on the left hand side then the remainder placed the diagonally opposite right hand corners. The numbers at the right hand side are the number of parts to be blended to attain the desired fat content. For the Algebraic equations method, the quantity each product and each product and the compositions of the ingredients must be known then a mass balance equations formed and solved (10).
The milk is the pasteurized or mildly heat treated depending on the type of cheese. This is done to reduce the harmful microorganisms and provide a conducive environment for starter cultures. Some varieties of cheese are made from raw milk and therefore does not need to be pasteurized. This milk has to be at least 60 days old to reduce the possibility of pathogen exposure. Milk used to making of grana, parmesan and other hard cheese should not be heated beyond 40 degrees Celsius to avoid whey expulsion, and tempering with the aroma and flavor. For these cheese, milk comes from selected dairy farms with frequent vet inspection (11). Pasteurization should be such that it kills all the bacteria that might threaten the quality of the cheese. However, some microorganisms such as Clostidium tyrobutricum can survive the pasteurization process and hence the need for more intense heat treatment.
After pasteurization, the milk is cooled or heat treated to 32 degrees Celsius so as to provide a conducive environment for growth of starter bacteria. The starter cultures together with the adjunct bacteria are added to the milk and held at a temperature of 32 degrees Celsius for almost 30 minutes to allow it to ripen. This allows growth of the bacteria and fermentation begins, lowering the pH and giving the cheese its flavor. According to Tetra Pak (12), there are three types of cultures: mesophilic cultures which operate a temperature between 25 and 40; thermophilic cultures operating at 50 degrees Celsius and adjunct cultures which provide a specific texture and taste to the cheese. In most cases, mixed strain cultures, which have two or more strains of bacteria with interdependent characteristics are used. The strain cultures produce lactic acid, carbon dioxide gas and also the aroma component. Carbon dioxide gas is responsible for the holes in round eyed cheese. Single strain cultures re applied when acid is to be developed and is used in protein degradation.
Rennet is then added to the milk so that curds are formed. After addition of the rennet, it has to remain undisturbed for about 30 minutes to form a strong coagulum. A low concentration of calcium in the cheese milk lead o soft coagulum hence high losses in casein and fats and also leads to poor syneresis. A 5 to 20 grams concentration of calcium chloride in 100 kg is sufficient to attain constant coagulation time and the required firmness of the curd (12). Adding more calcium chloride reduces the amount of rennet to be used. Disodium phosphate can also be added before addition of calcium chloride to produce low fat cheese. Carbon dioxide act as an inhibitor and adding to the milk improves its quality. Saltpeter is used to mask prevent formation of undesired gas though its used is being discouraged recently.
The curd is allowed to reach a pH of 6.4 then cut into small pieces and heated to 38 degrees Celsius. According to the University of Guelph (13), improper cutting makes the cheese lose its fines, therefore proper cheese cutting preserves the quality and yield of the cheese. The curd should be cut if it breaks cleanly on placing a blade at 45 degrees to the surface. Others use mechanical devices using thermal conductance, sonication and viscometry. The whey has to be drained from the vat then the curds form a mat. The cheese is then cut into small pieces to expel liquid. According to Meier (14), the smaller the pieces, the more whey is drained. Curds are cut, pressed and stacked on each other. This is repeated until much whey is expelled so that the cheese would have a crumbly dense texture after aging (15). Brining is done to add flavor, remove brine and form a rind which prevents growth of mould (6). Brining could be done in two ways, directly adding salt to the curds during milling or soaking the cheese in a brine solution (16). Cheese is now formed by placing the salted curd in hoops then pressed into blocks. The cheese is store in controlled temperature and humidity conditions. A correct pH, ventilation and air circulation is also needed. High moisture level makes the cheese to ripen faster. If the humidity level is low or air circulation is high, moisture would be drawn from the cheese resulting to a poor mold, bacterial and rind growth (17). A temperature of around 50 to 55 degrees is good for cheese aging. The effective humidity should not be less than 75 percent or higher than 95 percent of the relative humidity.
The core factors to consider in cheese packaging are oxygen and carbon dioxide permeability and the rate of vapour transmission in the packaging material. Modified atmospheric packaging are used for dairy products (like cottage cheese which has a life of up to 27 days) to increase their shelf life and help control fungal infections. The carbon dioxide used in cheese packaging varies from 10 to 100%, mixed with nitrogen gas used as an inert filler gas (18). A low concentration of carbon dioxide can improve the shelf life of some cheese. As an innovation in the cheese industry, active packaging methods have been introduced. These techniques include materials that absorb oxygen, moisture, odour and ethylene and also produce antioxidants, certain flavors, antimicrobials and carbon dioxide (18).
Increased research on cheese has led to further innovations on how to increase the cheese shelf life, such as the use of non-thermal food preservation technology. High pressure technology and pulsed electric fields are reliable in increasing the shelf life of cheese without altering their nutritional characteristics (19, 20). Supelveda et al (20) claim that using pulsed electric fields after pasteurization increases the shelf life up to 60 days. According to Engels et al (21), the increased consumer awareness on health diet has facilitated innovations in the cheese industry. Producers now have to produce high quality low salt and fat products. It has also led to improved cheese texture and flavor and also the preservation techniques of the fermented product. In optimizing cheese quality, knowledge on flavor attributes, biochemistry of flavor compounds and physiology of starter cultures is essential. Effective and efficient flavor and texture improvements calls for a systematic and thorough cultures screening during cheese making. NIZO food research developed models (MicroCheese and ScreenCheese models) to reduce cheese screening costs. These models are applied in texture and flavor formation (21). The models also offer a conducive platform in studying different aspects of cheese manufacturing such as screening of cultures required in fermentation, assessing safety and health aspects and assessing processing conditions. Cutting of curds is now done using a computer guided device. For cheese to ripen, it is recently placed in a nitrogen gas atmosphere and placed in the right temperature for a given time.
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