QUIZ 119 - 28/4 (solution)
QUIZ 119 - 28/4 (solution)
Time taking stage of freezing is
initial falling
thermal arrest
final falling
all of the above
source - wikipedia
Freezing is the process by which a substance transitions from a liquid to a solid state due to a decrease in temperature. However, the actual process of freezing is not an instantaneous event, but rather a time-dependent process that occurs over a range of temperatures. The time-taking stage of freezing is known as thermal arrest.
During thermal arrest, the temperature of the substance being frozen reaches its freezing point, which is the temperature at which the liquid phase of the substance transitions to a solid phase. At this point, the thermal energy of the substance is being released as the substance transitions to its solid state. However, the actual freezing process is delayed due to the need for heat transfer to occur.
Heat transfer is the process by which thermal energy is exchanged between two objects or substances. In the case of freezing, heat transfer occurs between the substance being frozen and the surrounding environment. As the temperature of the substance decreases, heat is transferred from the substance to the surrounding environment. However, during thermal arrest, the rate of heat transfer is not sufficient to allow the substance to freeze completely.
During this time, the temperature of the substance remains constant while the latent heat of fusion is being released. The latent heat of fusion is the energy required to convert a substance from a liquid to a solid phase. Once this energy has been released, the substance can begin to freeze and complete the transition from a liquid to a solid phase.
After thermal arrest, the substance enters the final falling stage, during which the temperature of the substance continues to decrease as the substance fully freezes. This final falling stage is the time period during which the substance completely transitions from a liquid to a solid phase.
Specific heat of frozen fish is
0.9 kcal
1 kcal
0.5 kcal
0.4 kcal
source - istock
The specific heat of frozen fish is 0.5 kcal/kg°C (kilocalories per kilogram per degree Celsius). Specific heat is the amount of heat required to raise the temperature of a unit mass of a material by one degree Celsius or Kelvin. This value of 0.5 kcal/kg°C is an approximate value and may vary depending on the specific type of fish, its composition, and other factors.´
Latent heat of melting ice is
1 kcal
0.5 kcal
0.9 kcal
80 kcal
The latent heat of melting ice is approximately 80 kcal/kg. Latent heat is the energy absorbed or released by a substance during a phase change without a corresponding change in temperature. In the case of melting ice, the latent heat is absorbed as the ice changes from a solid to a liquid phase at a constant temperature of 0°C.
The value of 80 kcal/kg is an approximate value and may vary slightly depending on the purity of the ice and the pressure at which the phase change occurs. However, it is a widely accepted value that is commonly used in thermodynamic calculations and experiments.
Ideal thermal arrest period is
2 hrs
3 hrs
1 hr
30 min
The ideal thermal arrest period during freezing can vary depending on the substance being frozen, the method of freezing, and the intended use of the frozen product. However, in general, the thermal arrest period typically lasts for around 30 minutes to 1 hour.
During thermal arrest, the temperature of the substance remains constant while the latent heat of fusion is being released. This period is important for ensuring that the substance freezes uniformly and completely, without the formation of ice crystals or other defects that can affect the quality and texture of the final product.
If the thermal arrest period is too short, the substance may not freeze completely or may develop uneven ice crystals, which can result in a lower quality product. On the other hand, if the thermal arrest period is too long, the substance may become over-cooled, which can also lead to the formation of ice crystals and a lower quality product.
Therefore, the ideal thermal arrest period during freezing is typically around 30 minutes to 1 hour, although this can vary depending on the specific circumstances of the freezing process.
Second stage of fish freezing curve is known as
thermal arrest
critical range
zone of maximum water crystallization
all of the above
The second stage of fish freezing curve is known as the "zone of maximum water crystallization".
During the freezing of fish or any other food product, the freezing curve represents the change in temperature over time as the product is cooled. The second stage of this freezing curve, which occurs after the initial cooling phase, is characterized by a rapid decrease in temperature as the water in the product begins to freeze. This rapid cooling causes the formation of ice crystals, which can lead to cellular damage and affect the texture and quality of the final product.
The zone of maximum water crystallization is the point in the freezing curve where the maximum amount of water is in the process of crystallizing, resulting in the rapid cooling and formation of ice crystals. This stage is important for ensuring that the product freezes quickly and uniformly, without the formation of large ice crystals or other defects that can affect the quality of the final product.
Thermal arrest and critical range are not typically used to describe the second stage of the fish freezing curve. Thermal arrest is a time-taking stage during which the temperature of the substance remains constant while the latent heat of fusion is being released. Critical range is a term used to describe a range of temperatures or other parameters within which a process or system must be maintained to ensure optimal performance or safety.
Causes of spoilage of fish
Bacterial
autolysis
freezing
chilling
On set and Resolution of rigor mortis depends upon
Lipid content
Protein content
Glycogen
Glycerol
The onset and resolution of rigor mortis in meat is dependent on the glycogen content of the muscles.
Rigor mortis is the stiffening of muscles that occurs after death. It is caused by a depletion of ATP in the muscles, which leads to the inability of the muscles to relax. The onset of rigor mortis can be delayed or accelerated depending on several factors, including the temperature of the carcass, the pH level of the muscles, and the glycogen content of the muscles.
Glycogen is a complex carbohydrate stored in the muscles, and it is a source of energy for muscle activity. If the glycogen levels in the muscles are high at the time of death, the onset of rigor mortis will be delayed. However, if the glycogen levels are low, the onset of rigor mortis will be accelerated.
The resolution of rigor mortis is also dependent on the glycogen content of the muscles. As the muscles begin to break down after death, they release enzymes that break down the glycogen into lactic acid. The lactic acid causes the pH of the muscles to decrease, which eventually causes the muscles to relax and the rigor mortis to resolve. However, if the glycogen levels in the muscles are low, the breakdown of glycogen and the production of lactic acid will be limited, which can result in a prolonged period of rigor mortis.
During spoilage, TMAO is converted into a substance that is responsible for fishery smell
Dimethyl amine
Trimethyl amine
Hypoxznthine
Inosine monophosphate
During spoilage, TMAO (trimethylamine oxide) is converted into trimethylamine (TMA), which is responsible for the "fishy" odor associated with spoiled fish.
TMAO is a compound that is naturally present in fish tissues. It helps to stabilize the proteins in the fish and prevent spoilage. However, when the fish begins to spoil, enzymes produced by bacteria break down the TMAO, releasing TMA. TMA has a strong, unpleasant odor, similar to that of rotting fish.
Dimethyl amine is a related compound, but it is not typically associated with fish spoilage. Hypoxanthine and inosine monophosphate are breakdown products of ATP (adenosine triphosphate) in the muscles of fish and other animals. They are not directly involved in the spoilage process, but their presence can be used as an indicator of the freshness of the fish, as their levels increase as the fish ages and spoils.
In vertebrates, ATP is produced from
Creatine Phosphate
Arginine phosphate
ADP
AMP
In vertebrates, ATP (adenosine triphosphate) is produced from ADP (adenosine diphosphate) through the process of cellular respiration, which occurs in the mitochondria of cells.
During cellular respiration, glucose and other molecules are broken down to produce energy in the form of ATP. The process involves several steps, including glycolysis, the citric acid cycle, and the electron transport chain.
Creatine phosphate and arginine phosphate are molecules that can provide a quick source of energy for muscle cells during short bursts of intense activity, such as weightlifting or sprinting. However, they do not produce ATP directly. Instead, they can donate phosphate groups to ADP to rapidly produce ATP. This process is called phosphagen system or creatine phosphate system.
AMP (adenosine monophosphate) is a molecule that is produced when ATP is broken down. It can be converted back into ATP through a process called phosphorylation, which involves the addition of a phosphate group. However, AMP itself does not directly produce ATP.
End product of the anaerobic metabolism in cephalopods
Lactic acid
Ethyl alcohol
Pyruvic acid
Octapine
The end product of anaerobic metabolism in cephalopods is usually not lactic acid or ethyl alcohol, but rather pyruvic acid.
Pyruvic acid is a molecule that is produced during the breakdown of glucose through the process of glycolysis, which is the first step in both aerobic and anaerobic metabolism. In aerobic metabolism, pyruvic acid is converted to acetyl-CoA and then enters the citric acid cycle to produce ATP through oxidative phosphorylation. However, in anaerobic metabolism, the lack of oxygen prevents the complete breakdown of pyruvic acid, and it is converted to other compounds, such as lactic acid or ethanol, in many organisms.
Cephalopods, including squid and octopuses, have unique adaptations that allow them to maintain aerobic metabolism even in low-oxygen environments. However, during periods of intense activity or stress, they may also use anaerobic metabolism to produce additional energy. In these cases, pyruvic acid is typically converted to other compounds, such as alanine, which can be used as an energy source.
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