Food Science Final Study Guide

Oil used for frying should ideally be replenished every 10 hours to ensure that it remains fresh and does not become rancid. Over time, oil can break down and develop off flavors and odors, which can affect the taste and quality of the fried food. Replenishing the oil regularly helps to maintain the desired taste and texture of the fried food.

Heat sensitive powders are typically dried using a spray dryer. A spray dryer is a device that uses hot air or gas to rapidly dry a liquid or slurry into fine particles. It works by atomizing the liquid into small droplets and then exposing them to a stream of hot air, causing the liquid to evaporate and leaving behind the dried powder. This method is commonly used for heat sensitive powders because it allows for quick and gentle drying, preventing any degradation or damage to the sensitive materials.

During frying, oils undergo various changes. Polymerization refers to the process in which the oil molecules combine to form larger molecules, resulting in the formation of a thick, sticky residue. Free fatty acid formation occurs when the oil breaks down, leading to the release of fatty acids. Oxidation refers to the reaction of the oil with oxygen, resulting in the formation of harmful compounds such as free radicals. Therefore, all of the given changes - polymerization, free fatty acid formation, and oxidation - occur in oils during frying.

Pathogenic microorganisms require certain conditions to grow and multiply in food. One of these conditions is a water activity level above 0.85. Water activity refers to the amount of available water in a substance, and a level below 0.85 is considered too low for pathogenic microorganisms to thrive. Therefore, if the water activity of a food is less than 0.85, it is unlikely that any pathogenic microorganisms will grow in it.

Freezer burn occurs when the moisture in food evaporates and then re-condenses on the surface, causing dry and discolored patches. Vacuum packaging helps eliminate freezer burn by removing air and reducing moisture in the package. Using a sealed package with a low water vapor transmission rate prevents moisture from entering the package. Maintaining a constant temperature during frozen storage prevents fluctuations that can lead to moisture loss. Therefore, all of these factors - vacuum packaging, sealed package with low water vapor transmission rate, and constant temperature - would help eliminate freezer burn.

Milk is homogenized to prevent creaming and separation of fat and liquid fractions. Homogenization is a process that breaks down the fat globules in milk into smaller particles, allowing them to disperse evenly throughout the liquid. This prevents the fat from rising to the top and forming a layer of cream. Homogenization also helps to create a smoother texture and improve the stability of the milk. It does not directly prevent the growth of microorganisms or the degradation of vitamins, which are separate processes that may be addressed through other methods such as pasteurization or refrigeration.

The vitamin content of the food does not affect heat and mass transfer during drying. Heat and mass transfer during drying are primarily influenced by factors such as temperature, humidity, atmospheric pressure, and vacuum. The vitamin content of the food is unrelated to the physical processes involved in heat and mass transfer during drying.

Freeze drying is the best drying technique for retaining the quality of the product. This process involves freezing the product and then removing the water through sublimation, where the ice turns directly into vapor without going through the liquid phase. This method helps to preserve the color, flavor, texture, and nutrients of the food, as it minimizes the damage caused by heat and oxidation. The low temperature used in freeze drying helps to maintain the integrity of the product, resulting in a higher quality end product compared to other drying techniques.

Milk is aseptically processed because it undergoes a process called ultra-high temperature (UHT) treatment, which involves heating the milk to a very high temperature for a short period of time to kill any bacteria or microorganisms present. This process allows the milk to be stored at room temperature for a longer period of time without spoiling, making it more convenient for consumers. Chunky soup, cream style corn, and canned beans, on the other hand, are typically processed using high heat and pressure in cans or jars, which is not considered aseptic processing.

The correct answer is a. 320-375oF. This temperature range is considered the optimum temperature for frying foods because it allows for the food to cook quickly and evenly while also creating a crispy exterior. Frying at temperatures lower than this range may result in greasy, undercooked food, while frying at temperatures higher than this range may cause the food to burn on the outside before it is fully cooked on the inside.

Increased levels of amino acids would promote Maillard browning in fried foods. Maillard browning is a chemical reaction that occurs between reducing sugars and amino acids when exposed to high heat. The reaction produces brown pigments and creates the characteristic flavors and aromas associated with cooked or fried foods. Therefore, an increased level of amino acids would provide more reactants for the Maillard reaction, resulting in enhanced browning.

Oranges for juice processing are graded according to their Brix:acid ratio. This ratio measures the sugar content (Brix) and acidity (acid) of the oranges. It is an important factor in determining the quality and taste of the juice. A higher Brix:acid ratio indicates a sweeter juice with a better balance of flavors. This grading system helps ensure that the oranges used for juice processing meet the desired standards for taste and quality.

Mashed potatoes are typically dried using a drum drier. A drum drier is a type of equipment that uses a rotating drum to dry and dehydrate food products. In the case of mashed potatoes, the drum drier helps to remove the moisture from the potatoes, resulting in a dried and powdered form. This method of drying allows for the preservation of the flavor and texture of the mashed potatoes while extending their shelf life.

The D-value represents the time required to destroy 90% of the microorganism or vitamin C at a specific temperature. In this case, the D-value for the microbe is 5 min, while the D-value for vitamin C is 15 min. Since a higher D-value indicates greater resistance to heat, we can conclude that vitamin C is more resistant to heat compared to the microbe. Therefore, option b is the correct answer.

Cobalt is added to glass bottles to produce a blue color. Cobalt is a transition metal that is known for its ability to impart a deep blue color to glass. When cobalt is added to the glass mixture, it reacts with the other components to create a blue hue. This makes cobalt an ideal choice for creating blue glass bottles. Selenium and iron oxides do not have the same color-inducing properties as cobalt, making them incorrect choices for this question.

Blanching is a cooking technique that involves briefly immersing food in boiling water or steam. It is commonly used to prepare fruits and vegetables before freezing or canning. Blanching helps to set the natural color of the food, reduces enzyme activity, and drives off respiratory gases. However, it does not improve the nutritional value of the food. In fact, blanching can cause some loss of nutrients due to the heat and water exposure. Therefore, option d is the correct answer as it does not align with the benefits of blanching.

Packages used in aseptic processing are sterilized with hydrogen peroxide. Hydrogen peroxide is a commonly used sterilizing agent due to its strong oxidizing properties. It is effective in killing a wide range of microorganisms, including bacteria, viruses, and fungi. The use of hydrogen peroxide helps to ensure that the packages are free from any potential contaminants, thus maintaining the sterility of the aseptic processing environment. Chlorine and quaternary ammonium are also used as disinfectants, but they are not typically used for sterilizing packages in aseptic processing.

The target organism for canning is Clostridium botulinum. This bacterium is responsible for causing botulism, a rare but serious illness that can lead to paralysis and even death. Canning is a method of food preservation that involves sealing food in airtight containers and heating it to destroy any bacteria, including Clostridium botulinum, that may be present. Therefore, none of the organisms listed in the options (Salmonella typhimurium, Staphylococcus aureus, and Listeria monocytogenes) are the target organism for canning.

Canned spam would primarily heat by conduction. Conduction is the transfer of heat through direct contact between objects or substances. In the case of canned spam, the heat is transferred from the heat source to the can, and then from the can to the spam through direct contact. This allows the heat to evenly distribute throughout the spam, ensuring it is heated thoroughly.

Mashed potatoes are not typically freeze dried because they have a high water content and a creamy texture, which makes them difficult to freeze dry without compromising their taste and texture. Freeze drying is commonly used for foods with low water content, such as fruits and vegetables, as it helps to preserve their nutritional value and extend their shelf life.

Shelf stable dairy creamers and milk receive UHT (Ultra High Temperature) thermal process. UHT process involves heating the product at a very high temperature for a short period of time, typically around 135-150°C (275-302°F) for a few seconds. This process helps to kill any harmful bacteria and microorganisms present in the product, ensuring its long shelf life without the need for refrigeration. UHT treatment also helps in preserving the flavor, texture, and nutritional value of the dairy products.

Peas in brine would heat the fastest because brine is a liquid that conducts heat more efficiently than the other options. Cream style corn, chili, and spam are all thicker and more viscous, which would slow down the heating process.

Reduced carbon dioxide does not slow down the respiration rate of apples because respiration in apples is primarily driven by the need for oxygen and the release of carbon dioxide. Therefore, reducing the carbon dioxide levels would not have a significant impact on the respiration rate. On the other hand, reduced oxygen levels (option a), elevated carbon dioxide levels (option b), and reduced temperature (option c) can all slow down the respiration rate of apples.

Small ice crystals formed in foods during direct freezing are the result of a fast freezing rate. When foods are rapidly frozen, the water molecules in the food do not have enough time to form large ice crystals. Instead, they freeze into smaller, more numerous crystals. This is beneficial because smaller ice crystals cause less damage to the food's cellular structure, resulting in better texture and quality when the food is thawed. On the other hand, a slow freezing rate allows for the formation of larger ice crystals, which can lead to a loss of moisture and a deterioration in the food's quality.

The D-value represents the time required to kill 90% of the microorganisms at a specific temperature. In this case, the D-value is 5 minutes. If the food is held for 15 minutes at the proper temperature, which is longer than one D-value, it means that more than 90% of the microorganisms would be killed. Therefore, the number of microbes left would be significantly reduced. Since the starting number of microbes is 20,000, it can be inferred that only a small fraction of them would remain, which is represented by the answer choice b. 20.

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Potato slices with a higher starch content tend to absorb more oil during frying. Therefore, the potato slice with the least amount of oil absorption would be the one with the lowest starch content. In this case, option d, which states that the potato slice has 65% starch, would absorb the least amount of oil during frying.

The cover hook of a can double seam is formed from the end curl. The end curl is the curled edge of the can lid that is folded over the flange of the can body to create a secure seal. This end curl provides stability and prevents the lid from coming off the can. The sealing compound is applied between the end curl and the flange to further ensure a tight seal. The can flange is the flat, horizontal surface of the can body that the lid rests on.

Pressure sterilization is a method used to kill microorganisms and extend the shelf life of certain foods. However, none of the foods mentioned in the options require pressure sterilization. Orange juice, apples, and tomatoes have pH levels below 4.6, which is considered acidic enough to inhibit the growth of most microorganisms. Therefore, none of these foods require pressure sterilization.

Aluminum is added to a laminated package to serve as a moisture and oxygen barrier. Aluminum is highly impermeable to moisture and oxygen, making it an effective barrier material. It helps to protect the contents of the package from moisture and oxygen, which can cause spoilage or degradation. Additionally, aluminum is lightweight and flexible, making it a suitable choice for packaging materials.

During freezing and frozen storage of foods, not all of the solutes freeze. Freezing causes water to form ice crystals, leaving behind a concentrated solution of solutes. This is because water molecules freeze at a lower temperature than solutes, so the solutes remain in a liquid state while the water freezes. Therefore, option c is the correct answer as it does not occur during freezing and frozen storage of foods.