1. Chilling injury: When stored at low temperature, although the storage temperature of some fruits and vegetables is not lower than their freezing point, when the storage temperature is lower than a certain temperature limit, these fruits and vegetables will show a series of physiological diseases, and their normal physiological mechanisms can be hindered. This phenomenon of physiological diseases caused by low temperature is called chilling injury.
2. Osmosis: refers to the diffusion of solvent from low concentration to high concentration reading solution through semi-permeable membrane under the action of osmotic pressure.
3. Meat coloring agent: refers to a kind of substance that has no coloring function itself, but can improve the coloring condition well
when it is used together with nitrite, such as ascorbic acid.
4. Sublimation drying: a drying method in which food is pre-frozen and then moisture is removed by sublimation under vacuum.
5. radiation odor: through radiation treatment and heat treatment, the self-oxidation process of fats in agricultural products and their products can be accelerated, thus generating odor.
second, multiple-choice questions (choose one or more correct answers from the four selected answers of the following questions, and write their code numbers in the corresponding positions on the answer sheet
times. If the answers are wrong or not selected, the question will not score. 2 points for each small question, 3 points for * * *.
1. Phosphate is a kind of substance with multiple functions, which can obviously improve the quality in food processing.
its mechanism is:. a, b, D
A, increasing the pH value of the system; B, increasing the ionic strength; C, emulsified oil; D, dissociate actin. 2. which of the following sugars has the largest diffusion coefficient: A
A, glucose; B, sucrose; C, dextrin; D, maltose.
3. The pickling methods that can not only ensure the uniform distribution of salt in raw materials' tissues, but also avoid the oxidative deterioration of raw materials when they come into contact with air
are: B
A, dry pickling; B, wet pickling method; C, injection method; D, mixed
combined pickling method.
4. which of the following sugar methods should be used to make candied fruit A
A, such as candied green plum, candied red bayberry, honey loquat and honey cherry, and the one-time cooking method should be adopted; B, multiple boiling method; C, cooking under reduced pressure; D, honey.
5. the cool taste of preserved eggs comes from preserved eggs: C
A, keto acid; B, hydrogen sulfide; C, ammonia; D, sodium glutamate.
6. Which method is the least carcinogenic when food is smoked? D
A, cold fumigation; B, thermal fumigation; C, warm fumigation; D, liquid fumigation 7. Which of the following processes is the fruit and vegetable drying process:
D
A, which is both sterilization and enzyme inactivation; B, sterilization does not kill the enzyme; C, inactivating enzyme without sterilization; D, neither sterilization nor enzyme inactivation. 8. Use < P > to inhibit the germination of potatoes, onions, etc. To kill the pathogenic parasites of insects and meat and delay the post-ripening radiation of fresh food, the dosage is: A
A, low dose radiation; B, medium and low dose irradiation; C, medium and high dose irradiation; D, high dose irradiation.
9. The following can be used as radiation sources: Abd
A, 6Co,; B,137Ce C,226Ra； D, electron beam accelerator.
1. For crops sensitive to CO2, the combination of oxygen and carbon dioxide during controlled atmosphere storage should be: BD
A, with double indexes (the total is about 21%); B, the low indicator in the double indicators (the sum is less than 21%); C, the medium index in the double index < P > (the sum is less than 21%); D, 2 single indicator.
1
partial pressure of gas %
2 CO2
venting time
/d
11. According to the transformation of CO2 in the controlled atmosphere storage period, determine what kind of gas management method is shown below: BA, venting method;
B, controlled atmosphere method; C, CO2-filled natural drop 2 method; D, airflow method. 12. what kind of food is mainly cooled by ice water cooling method:
A
A, fish cooling; B, rapid cooling of vegetables; C, meat cooling; D, eggs are cooled. 13. at which stage did the largest ice crystal formation zone
form when food was frozen: CA, the initial stage; B, supercooling point stage; C, middle stage; D, final
stage.
14. According to the characteristics of fluid flow, the flow of gas-solid two-phase fluid has the following three motion states: ABDA, fixed
bed stage; B, fluidized bed stage; C, boiling bed stage; D, pneumatic conveying stage. 15. Gluten protein package in flour
includes: CDA, glutenin; B, globulin; C, gliadin; D, glutenin.
Third, judge the explanation question (first judge whether the proposition is right or wrong, then explain the reasons for right or wrong, judge 1 point and explain 2 points
; Wrong judgment, the whole question does not score. 3 points for each small question, ***18 points)
1. In meat curing, the purpose of adding sugar is to buffer the taste of cured meat and make it soft. (×)
Judgment: In meat curing, the purpose of adding sugar is not only to buffer the taste of cured meat and make it soft, but also to have a small amount of antiseptic effect.
2. The pine flowers in the preserved eggs are crystals formed by the mixture of free amino acids produced during protein decomposition and inorganic salts in the eggs. (√)
3. It is safe and hygienic to eat irradiated agricultural products and their products below 1kGy. (√)
4. Fruits and vegetables still have vitality after picking, and their respiration can play a role in regulating gas, so
2
Modified atmosphere preservation is mainly used for fruit and vegetable preservation. (×)
Judgment: Modified atmosphere preservation can be used for the preservation of fruits and vegetables and other foods.
5. For soft or fragile foods, such as strawberries, cucumber slices, green beans, asparagus, fried eggplant and so on, a vibrating fluidized quick-freezing device can be used
. (×)
Judgment: The vibration fluidized quick-freezing device has a large movement range, and it is not easy to use when quick-freezing soft or fragile foods, such as strawberry
cucumber slices, green beans, reed and fried eggplant, are damaged.
6. When making sand-returning candied fruit, the proportion of invert sugar can be appropriately increased to achieve the purpose of sand-returning. (×) Judgment < P > indicates that the proportion of invert sugar is too high, and the candied fruit is easy to absorb moisture, which is not conducive to sand returning. Therefore, when making honey money for sand returning, the ratio of invert sugar should not be too high.
fourth, short answer questions (answer the main points and explain them concisely. 4 points for each small question, ***2 points) 1. How did the fresh egg change during the salting process, making it a salted egg with unique flavor.
A: The high concentration of salt forms a concentration gradient inside the fresh egg, which permeates the solute continuously, and the viscosity of the egg yolk keeps rising
, and finally it becomes a center, and the fat in the egg yolk is also released, which increases the flavor; At the same time, due to the continuous infiltration of water from egg yolk to the outside of < P >, the water content of protein was increased and the tenderness of protein was improved. 2. Compare the difference between pure water freezing process and food freezing process < P >.
a: the difference between pure water freezing process and food freezing process is that the initial freezing temperature is different, and the food solution contains soluble substances, and the initial freezing temperature is lower than that of pure water; Second, when cooled to a certain temperature, food can not be completely frozen in a short temperature range like pure water, and there is still some unfrozen water. 3. Effect of sugar on dough structure.
Answer: Glutinous protein in flour swells and moistens to form a large amount of gluten, which enhances the elasticity of dough and reduces the viscosity accordingly
However, if syrup is added to dough, due to the hygroscopicity of sugar, it not only absorbs the free water between protein colloidal particles, but also increases the external concentration of colloidal particles, which makes the water inside the colloidal particles reverse osmosis, thus
3
reducing the water absorption of protein colloidal particles. The hydration of sugar limits the formation of a large number of gluten, which is closely related to crisp dough < P >.
4. Briefly describe the principle of reasonable selection of drying process conditions
A: (1) The selected process conditions should make the evaporation rate of water on the food surface equal to its internal diffusion rate
as far as possible, and avoid forming a large temperature gradient inside the food to avoid slowing down the drying rate and surface hardening.
(2) In the constant-rate drying stage, because all the heat absorbed by food is used for evaporation of water, the evaporation rate of surface water is
degrees, which is equivalent to the diffusion rate of internal water. Therefore, an appropriate higher air temperature can be adopted to speed up the drying process.
(3) In the later stage of drying, the relative humidity of air should be adjusted according to the expected water content of dry products. (4) In the drying stage with decreasing rate < P >, because the evaporation rate of water on the surface of food is faster than the diffusion rate of water inside, the surface temperature will gradually increase and reach the dry bulb temperature of air < P >.
5. according to the action principle of high CO2 and low CO2, the utility and characteristics of modified atmosphere technology are briefly described. Answer: 1. Delaying the aging process (ripening and aging) of fruits and vegetables
2. Alleviating some physiological diseases in storage-chilling injury 3. Inhibiting the role of microorganisms 4. Preventing and controlling insect pests
5. Suppressing or delaying other adverse chemical changes that affect the decline of food quality
5. Discussion topic (* * 1 points).