CHAPTER BUTTER.pdf

# Dairy product processing techniques Dairy product processing techniques are essential for ensuring the safety, quality, and shelf-life of milk and its derivatives by manipulating their composition and physical characteristics. These techniques aim to protect consumers from diseases, extend storage life, standardize nutrient content, and stabilize the milk's emulsion [7](#page=7) [8](#page=8). ### 1.1 Overview of processing techniques Commonly employed dairy processing techniques include separation, clarification, standardization, homogenization, and thermal processing such as pasteurization and sterilization. Other methods like freezing or the addition of sucrose to concentrated milk are also utilized [8](#page=8). ### 1.2 Separation and clarification Separation and clarification are processes that remove undesirable components from milk, primarily based on differences in density [9](#page=9). #### 1.2.1 Centrifugation Centrifugation is the primary method for separation and clarification. It relies on the density differences between milk serum and the particles being separated. Somatic cells are heavier than milk serum, while fat globules are lighter [9](#page=9). #### 1.2.2 Clarification A clarifier removes somatic cells and bacterial cells from raw milk before pasteurization by allowing these heavier particles to remain within the equipment while the clarified milk flows out as the sole effluent stream [10](#page=10) [9](#page=9). #### 1.2.3 Separation A separator also operates on the principle of centrifugation but results in two distinct streams: skim milk (with reduced fat content) and cream (with concentrated fat) [10](#page=10). #### 1.2.4 Creaming In raw milk, if left to stand, fat globules naturally rise to the surface due to their lower density, a phenomenon known as creaming [12](#page=12). ### 1.3 Standardization Standardization is the process of adjusting the fat content of milk to a desired level [13](#page=13). #### 1.3.1 Purpose of standardization The primary purpose of separation is to produce skim milk and cream, which can then be recombined to achieve a specific, desired fat content in the final product [13](#page=13). #### 1.3.2 Methods of standardization Standardization can be performed manually or using automated machinery. Examples of standardized milk include low-fat milk (1% to 2% milk fat) and whole milk (3.25% milk fat) [13](#page=13). ### 1.4 Thermal processing: Pasteurization Pasteurization is a thermal process that uses heat to destroy pathogenic bacteria and enzymes, thereby extending the refrigerated shelf life of milk without significantly altering its flavor. The specific times and temperatures are mandated by regulatory agencies and are typically based on the inactivation of \_Listeria monocytogenes [14](#page=14). #### 1.4.1 Methods of pasteurization There are three primary methods of pasteurization: 1. **Vat/batch pasteurization:** Milk is heated to 62.8 degrees Celsius and held for 30 minutes [16](#page=16). 2. **High-temperature-short-time (HTST) pasteurization:** This is a continuous flow process where milk is rapidly heated to 71.5 degrees Celsius in a heat exchanger, held for 15 seconds, and then quickly cooled to 4 degrees Celsius [16](#page=16). 3. **Ultra-high temperature (UHT) pasteurization:** This method involves much higher temperatures (130–140 degrees Celsius) for very short durations (2–6 seconds) [16](#page=16). > **Tip:** UHT processing significantly extends shelf life and can allow for ambient storage, but it may cause more noticeable flavor and color changes compared to HTST pasteurization [16](#page=16) [17](#page=17). ### 1.5 Thermal processing: Sterilization Sterilization aims for the complete destruction of microorganisms, including spores [17](#page=17). #### 1.5.1 Methods of sterilization Sterilization can be achieved through retort processing or ultra-high temperature (UHT) sterilization followed by aseptic packaging [17](#page=17). * **Retort sterilization:** Milk treated via retort processing often exhibits browning discoloration, a cooked or caramelized flavor, and some loss of nutritional components, making it less suitable for direct consumption but useful as an ingredient in food preparation [17](#page=17). * **UHT sterilization with aseptic packaging:** Milk treated by UHT at temperatures ranging from 135 to 150 degrees Celsius for a few seconds can achieve a product virtually free of spores with significantly less browning than conventional in-can sterilization. Unconcentrated whole and skim milk processed by UHT are then aseptically packaged, providing an unrefrigerated shelf life of several months [18](#page=18). > **Example:** UHT milk is commonly available in shelf-stable packaging that does not require refrigeration until opened [19](#page=19). ### 1.6 Homogenization Homogenization is a standard procedure designed to stabilize the fat emulsion in milk, preventing creaming by breaking down fat globules into smaller, more uniform sizes [20](#page=20). #### 1.6.1 Process of homogenization The process involves forcing milk through small orifices (apertures) under high pressure, typically between 1700 and 2500 pounds per square inch (psi). This creates intense turbulence, causing the fat globules to break up into smaller ones [20](#page=20). #### 1.6.2 Conditions affecting homogenization Several factors influence the size and dispersion of fat globules during homogenization, including temperature, pressure, and the concentration of the fat phase. Homogenizers are often integrated with pasteurizers and operated near pasteurization temperatures to minimize microbial contamination [22](#page=22). #### 1.6.3 Impact on fat globule size In raw milk, fat globules typically range from 0.2 to 15 micrometers ($\\mu$m) in diameter. After homogenization, the fat globules are significantly reduced in size, with most not exceeding 1 micrometer ($\\mu$m) in diameter, and none larger than 2 micrometers ($\\mu$m) [23](#page=23). * * * # Production of sweetened condensed milk This section details the manufacturing process of sweetened condensed milk (SCM), focusing on standardization, preheating, concentration, sugar addition, controlled crystallization via lactose seeding, and final packaging to ensure a smooth, stable product [25](#page=25) [27](#page=27) [28](#page=28) [29](#page=29) [30](#page=30). ### 2.1 Overview of the SCM production flow The production of SCM follows a general flow starting from raw milk, which undergoes several critical processing steps before being canned. The main stages include milk standardization, preheating, homogenization, concentration via vacuum evaporation, sugar addition, controlled cooling and seeding with lactose for crystallization, and finally, sealing and labeling of the cans [25](#page=25) [27](#page=27). ### 2.2 Pre-concentration steps #### 2.2.1 Milk standardization and preheating The process begins with standardizing the raw milk to achieve a specific ratio of milk fat (MF) to non-milk solids (NMS). Following standardization, the milk is preheated and then homogenized [27](#page=27). #### 2.2.2 Sugar addition and pasteurization After preheating and homogenization, the standardized milk is blended with sugar. This sugar-milk blend is then pumped into large stainless steel tanks for pasteurization [27](#page=27). ### 2.3 Concentration process The blend of heated, standardized whole milk and sugar is then condensed to the required consistency in a vacuum condensing pan. The goal of concentration is to reduce the moisture content to a level that results in supersaturation with respect to lactose [27](#page=27) [28](#page=28). #### 2.3.1 Target composition and supersaturation When the correct concentration is reached, the product typically contains less than 8.5% milk fat (MF), approximately 28% total milk solids, and about 44% sucrose. At this stage, the moisture content is reduced sufficiently to achieve supersaturation concerning lactose [28](#page=28). ### 2.4 Crystallization and cooling #### 2.4.1 Importance of rapid crystallization Crystallization must be performed rapidly to prevent the finished product from becoming "sandy" in texture [28](#page=28). #### 2.4.2 Lactose seeding for texture control The cooled, concentrated milk is seeded with very fine lactose crystals. This lactose seeding is crucial for controlling the size of the lactose crystals and avoiding grittiness in the SCM. The added small lactose crystals (seeds) act as nuclei, initiating and guiding the subsequent growth of lactose crystals [28](#page=28) [30](#page=30). > **Tip:** Lactose seeding is essential for achieving a smooth, creamy texture in sweetened condensed milk by preventing the formation of large, gritty lactose crystals. #### 2.4.3 Seeding conditions The seeding process must occur at an optimum temperature to facilitate crystal growth. Sufficient time and agitation are necessary to ensure adequate heat transfer and uniform distribution of the seed crystals throughout the milk mass. Agitation may be required for as long as 24 hours, depending on the agitation speed and the size of the tank [30](#page=30). At this point, the milk achieves a thick, smooth texture and a creamy color [28](#page=28). ### 2.5 Final packaging #### 2.5.1 Can filling The cans are completely filled to prevent any presence of air within the packaging [29](#page=29). #### 2.5.2 Sealing and labeling Following complete filling, the cans are sealed and subsequently labeled [29](#page=29). * * * # Production of evaporated milk The production of evaporated milk involves a series of critical steps focused on concentrating milk through water removal, followed by sterilization to ensure product stability and safety [31](#page=31). ### 3.1 Overview of the process The manufacturing flow for evaporated milk begins with the raw milk, which may undergo clarification or filtration. This is followed by standardization, preheating, concentration via evaporation, homogenization, cooling, re-standardization, filling into cans, and finally, sterilization and cooling. The final product is then dried and labeled [31](#page=31). ### 3.2 Standardization Milk is first standardized based on the ratio of milk fat (MF) to non-milk solids (NMS) [32](#page=32). ### 3.3 Preheating Preheating, also known as forewarming, is a crucial step in the evaporation process. The milk is typically heated to temperatures between 38 degrees Celsius and 82 degrees Celsius for 20 to 30 minutes, or alternatively, heated to 121 degrees Celsius for 2 to 3 minutes [32](#page=32). This thermal treatment serves two primary purposes: * **Reduction of bacterial count:** This helps to minimize spoilage microorganisms [32](#page=32). * **Stabilization of milk proteins:** This prevents coagulation or "breaking" of the milk during the subsequent sterilization process [32](#page=32). > **Tip:** The effectiveness of preheating in preventing coagulation during sterilization is a key quality control measure in evaporated milk production. ### 3.4 Concentration via evaporation After preheating, the milk is drawn into a double-effect evaporator. In this stage, approximately half of the water content is removed from the milk. This results in a concentrated milk product that is roughly twice the concentration of the original milk, hence a 2 to 1 concentration ratio [32](#page=32) [33](#page=33). ### 3.5 Homogenization and cooling The 2 to 1 concentrated milk is then homogenized. Homogenization helps to break down fat globules, preventing creaming during storage and ensuring a uniform product. Following homogenization, the milk is cooled [33](#page=33). ### 3.6 Re-standardization After cooling, the milk undergoes re-standardization. This step involves adjusting the composition of the concentrated milk, typically by adding water or condensed skim milk, to achieve the desired final product specifications [33](#page=33). ### 3.7 Filling and sterilization The re-standardized milk is then filled into cans. These cans are subsequently sealed and sterilized to ensure a long shelf life and microbiological safety. The final step involves drying and labeling the cans [31](#page=31) [33](#page=33). * * * # Production of butter This section details the process of producing butter, commencing with the separation of cream from milk and progressing through cream preparation, churning, washing, salting, and final packing [35](#page=35) [41](#page=41). ### 4.1 Definition and composition of butter Butter is defined as a spread made by churning cream separated from milk. It must contain at least 80% milk fat and can be produced with or without added salt. Critically, butter is an oil-in-water emulsion, a reversal from milk's natural oil-in-water emulsion structure. The most common butter available in markets is made from pasteurized sweet cream and includes added salt [36](#page=36). ### 4.2 Separation of cream Cream is the fatty portion of milk that rises to the top when milk is allowed to stand for an extended period. While gravity separation can occur, cream is more rapidly separated using centrifugal force with a cream separator. The fat content of the cream can vary significantly, depending on the fat content of the original milk and the method of separation employed [38](#page=38) [42](#page=42). In the cream separation process, milk is introduced into a rapidly revolving disc system within the cream separator. The specific gravity of buttermilk globules is approximately 0.93 at 15°C, while that of whole milk is about 1.032. Centrifugal force expels the non-fatty components of milk to the outside of the separator, while the butterfat, being lighter, gravitates towards the center. Typically, cream produced through this method contains between 30% and 35% butterfat [42](#page=42). > **Tip:** Understanding the difference in specific gravity between fat globules and the non-fatty milk components is key to comprehending how centrifugal separation works [42](#page=42). ### 4.3 Preparation of cream The preparation of cream involves two main approaches depending on the desired butter flavor: sweet cream or sour cream [44](#page=44). * **Sweet cream butter:** Fresh cream is directly pasteurized [44](#page=44). * **Sour cream butter:** To achieve a 'sour' flavor, cream is first allowed to sour naturally. Its acidity is then standardized to approximately 0.25% lactic acid, often by adding sodium carbonate or lime, before pasteurization. The 'sour' flavor is further refined by inoculating the pasteurized cream with a culture of \_Streptococcus lactis [44](#page=44). The action of an emulsifier, like those found in milk fat, is illustrated by a hydrophilic head and a lipophilic tail, which allows it to interact with both water and oil phases. This property is fundamental to understanding emulsion inversion during butter production [40](#page=40) [45](#page=45). ### 4.4 Churning Churning is the mechanical agitation process that transforms cream into butter. Cream, initially, is a colloid suspension of small fat globules in a watery solution, an oil-in-water (o/w) emulsion. When subjected to sufficient mechanical agitation at a controlled temperature, typically around 10°C, this suspension undergoes an inversion [45](#page=45). During this inversion, the fat and a portion of the aqueous solution separate to form granules of butter, while the remaining liquid, known as buttermilk, is drawn off [45](#page=45). > **Tip:** The temperature during churning is critical; if too high, the fat can melt, preventing proper emulsion inversion. If too low, the fat globules will be too rigid to break and agglomerate [45](#page=45). ### 4.5 Washing and adding salt After the buttermilk has been drawn off from the churned butter granules, the butter is typically washed with water. This washing step removes residual buttermilk, which can negatively affect the keeping quality and flavor of the butter [47](#page=47). Salt is then added to the butter. The typical concentration of salt used ranges from 2.5% to 3%. Salt serves multiple purposes: it enhances the flavor of the butter, inhibits the growth of undesirable microorganisms such as yeasts and molds, and also acts to suppress the activity of proteolytic and lipolytic bacteria [47](#page=47). Some modern butter-making processes incorporate machinery to homogenize the butter after salting. This homogenization aims to subdivide the water globules within the butter, contributing to a more uniform texture and potentially improving its quality [47](#page=47). ### 4.6 Packing For optimal keeping quality, it is desirable to pack the butter immediately after the salt has been added and the butter has been adequately "worked". Working the butter, which involves further manipulation, helps to distribute the salt and moisture evenly and develop the final texture. Proper packing is crucial to protect the butter from oxidation, moisture loss, and absorption of odors from the environment, thus preserving its freshness and quality [48](#page=48). * * * # Food safety and storage considerations This section addresses the critical importance of consumer safety in the food industry, particularly concerning product recalls and measures to prevent foodborne illnesses, alongside practical storage recommendations for specific food items. ### 5.1 Consumer safety and product recalls Consumer safety is paramount in the food industry, with product recalls serving as a crucial mechanism to protect the public from potential harm. These recalls are initiated when a food product is found to pose a health risk, such as contamination or the presence of undeclared allergens, which could lead to illness or adverse reactions. The consumer's reaction to a recall can range from concern and apprehension to a complete loss of trust in the brand or manufacturer [3](#page=3). From a food technologist's perspective, recalls highlight the complexities of food production, supply chain management, and the continuous need for robust quality control systems. Analyzing a recall involves understanding the root cause of the safety issue, evaluating the effectiveness of the recall process, and considering how such incidents might be prevented in the future. Furthermore, it's important to relate current recalls to historical events, such as the Fonterra product recall, to identify recurring challenges and evolving best practices within the industry [3](#page=3). ### 5.2 Storage recommendations Effective storage practices are essential for maintaining food quality, safety, and extending shelf life. Specific recommendations are provided for certain types of products. #### 5.2.1 General storage guidelines When storing certain food products, particularly those that may be sensitive to environmental conditions, the following guidelines are recommended: * **Use a tight container**. This helps to prevent contamination from external sources and can maintain the product's integrity [54](#page=54). * **Maintain anaerobic conditions**. This implies storing the product in an environment with limited or no oxygen, which can be critical for preventing spoilage and the growth of certain microorganisms [54](#page=54). * **Preferably use a thermos**. A thermos is ideal for temperature control, ensuring the product remains at a stable, optimal temperature, whether hot or cold [54](#page=54). * **Alternatively, store in a cabinet for 6 hours or overnight**. If immediate temperature control is not feasible, a cabinet can serve as a temporary storage solution for a limited duration [54](#page=54). #### 5.2.2 Storage considerations for dairy products While not explicitly detailed in terms of specific storage instructions beyond general principles, dairy products fall under the broad category of food items requiring careful handling to ensure safety and quality. Their susceptibility to bacterial growth necessitates adherence to proper temperature control and hygienic storage practices [1](#page=1). > **Tip:** The principles of maintaining anaerobic conditions and temperature control are particularly relevant for products that may be sensitive to oxidation or heat, such as certain fermented foods or probiotics, aligning with the broader context of food safety. ### 5.3 Benefits of probiotics Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host. While the document briefly mentions their benefits, further elaboration would typically detail their positive impact on gut health, immune function, and potentially other physiological processes. Storage considerations discussed earlier may be directly applicable to products containing probiotics to ensure their viability and efficacy [55](#page=55). * * * ## Common mistakes to avoid * Review all topics thoroughly before exams * Pay attention to formulas and key definitions * Practice with examples provided in each section * Don't memorize without understanding the underlying concepts

| Term | Definition | |------|------------| | Cream | The fatty portion of milk that rises to the surface when milk is allowed to stand, or is rapidly separated by centrifugal force. It is an oil-in-water emulsion used as a base for butter production. | | Pasteurization | A thermal process that uses heat to destroy disease-causing bacteria and enzymes in milk. This extends the refrigerated shelf life of milk without significantly altering its flavor. | | Sterilization | The complete destruction of microorganisms in a product, often achieved through retort processing or ultra-high temperature (UHT) treatment followed by aseptic packaging. This results in a product with a long, unrefrigerated shelf life. | | Homogenization | A process involving forcing milk through small apertures under high pressure, creating intense turbulence that breaks down fat globules into smaller, uniformly dispersed particles. This stabilizes the fat emulsion against gravity separation. | | Standardization | The process of adjusting the fat content of milk to a desired level. This is typically accomplished by separating the milk into cream and skim milk, then recombining them to achieve specific fat percentages, such as for low-fat or whole milk. | | Skim milk | Milk from which most of the fat has been removed, typically through centrifugation. It has a significantly lower fat content compared to whole milk. | | Whey products | Products derived from whey, which is the liquid remaining after milk has been curdled and strained during the process of making cheese or casein. Whey products can provide functionality in food applications. | | Emulsification capability | The ability of a substance, like milk components, to help mix and stabilize immiscible liquids, such as oil and water, preventing them from separating. | | Viscosity | A measure of a fluid's resistance to flow. Higher viscosity means the fluid flows more slowly. Milk constituents can contribute to the viscosity of dairy products. | | UHT (Ultra-High Temperature) processing | A method of thermal processing where milk is heated to very high temperatures (130–140°C or higher) for a very short duration (2-6 seconds). This significantly reduces microbial load and extends shelf life. | | Aseptic packaging | A method of packaging food products, such as UHT-treated milk, in sterile containers in a sterile environment. This allows the product to be stored at room temperature for extended periods without refrigeration. | | Lactose seeding | The process of adding small, pre-formed lactose crystals to cooled, concentrated milk. These seeds act as nuclei, controlling the size and preventing grittiness by initiating the growth of subsequent lactose crystals during the production of sweetened condensed milk. | | Super saturation | A condition where a solution contains more dissolved solute than it can normally hold at a given temperature and pressure. In sweetened condensed milk production, the lactose becomes supersaturated, which is managed by seeding to control crystallization. | | Butter | A spread made by churning cream, containing at least 80% milk fat. It is an oil-in-water emulsion, unlike milk which is an oil-in-water emulsion. | | Churning | The process of agitating cream mechanically to invert its emulsion from oil-in-water to water-in-oil, separating the fat into granules that form butter, with the remaining liquid being buttermilk. | | Buttermilk | The liquid remaining after cream has been churned into butter. It is a by-product of butter production. | | Emulsifier | A substance that helps to stabilize an emulsion by forming a film around the dispersed particles, preventing them from coalescing. The structure of an emulsifier typically involves a hydrophilic (water-attracting) head and a lipophilic (fat-attracting) tail. | | Microorganisms (m/o) | Microscopic organisms, such as bacteria, viruses, and fungi, that can cause spoilage or disease. Their control is a primary concern in dairy processing. |