تخزين المحاصيل الزراعية

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Questions and Answers

ما هو المحصول الذي يحتاج إلى درجة حرارة أقل من 0º م لتخزينه بدون ضرر؟

الطماطم

البرتقال

البطاطس

الموز (correct)

أي من المحاصيل التالية يمكن تخزينه عند درجة حرارة 5º م بدون الإضرار به؟

الخس

الجزر

التفاح (correct)

الكوسة

ما هي المخاطر المحتملة عند تخزين محصول في درجات حرارة أقل من درجته الآمنة؟

ظهور العفن

زيادة الحموضة

تساقط الزهور

تلف الأنسجة (correct)

أي من المحاصيل التالية يعتبر الأكثر حساسية للبرودة؟

الجوافة Signup and view all the answers

أي درجة حرارة التالية تُعتبر آمنة لتخزين الخضروات الجذرية؟

3º م Signup and view all the answers

ما تأثير تدفئة الثمار المتكررة أثناء التخزين المبرد؟

تقليل حساسية الثمار لأضرار البرودة Signup and view all the answers

كم من الوقت تحتاج درجة حرارة المخزن للارتفاع خلال عملية التدفئة المتكررة؟

ساعات كل عدة أيام Signup and view all the answers

ما الغرض من التخلص من مركبات التنفس الوسطية؟

تقليل حساسية الثمار لأضرار البرودة Signup and view all the answers

ما الذي يحدد فترة التدفئة أثناء التخزين المبرد؟

التكرار الزمني للتدفئة Signup and view all the answers

لماذا يتم رفع درجة حرارة المخزن لعدة ساعات كل عدة أيام؟

لتقليل تأثير البرودة على الثمار Signup and view all the answers

ما هي العلامة المميزة التي تشير إلى انهيار مائي في الثمرة؟

ظهور قشرة ثمرية اسفنجية ومائية المظهر Signup and view all the answers

أي من العوامل التالية يمكن أن يؤدي إلى تغير لون اللب في بعض أصناف التفاح؟

انهيار مائي Signup and view all the answers

ما الذي يميز الشجرة التي تعاني من انهيار مائي؟

ظهور قشرة الثمار بشكل اسفنجى Signup and view all the answers

ما هي أحد العوامل المحتملة لتأثير انهيار الماء على مظهر الثمار؟

وجود فائض من المياه في التربة Signup and view all the answers

كيف يظهر انهيار الماء في الفواكه مثل البرتقال؟

مظهر اسفنجى للقشرة Signup and view all the answers

ما الذي يتسبب في تحول الأنسجة إلى مائية في كمثري بارتلت؟

الإصابة بالكائنات الحية الدقيقة الممرضة Signup and view all the answers

ما هي النتيجة الرئيسية لفقدان الثمار البستانية لمقدرتها على مقاومة الكائنات الحية؟

سهولة الإصابة بالكائنات الدقيقة Signup and view all the answers

ما الذي يساهم في تلف الثمار وظهور الأنسجة المائية؟

فقدان القدرة على المقاومة Signup and view all the answers

أي من العوامل التالية ليس له علاقة بإصابة الثمار بالكائنات الدقيقة؟

تحسين الزراعة العضوية Signup and view all the answers

ما هو التأثير المباشر لفقدان الفواكه لمقدرتها على مقاومة البكتيريا؟

زيادة الحساسية للإصابة Signup and view all the answers

ما هي إحدى النتائج السلبية الرئيسية الناتجة عن نقص العناصر الغذائية في النباتات؟

نوية أو التشقق Signup and view all the answers

أي من الخيارات التالية يعبر عن أثر سلبي يترافق مع نقص العناصر الغذائية؟

تشوهات الثمار Signup and view all the answers

ما هو العرض الرئيسي الذي يُظهر تأثير نقص العناصر الغذائية على النباتات؟

االخضرار Signup and view all the answers

ما الذي لا يعتبر من نتائج نقص العناصر الغذائية في النباتات؟

زيادة في إنتاج الثمار Signup and view all the answers

ما هي الظاهرة التي قد تحدث نتيجة لعدم وجود تغذية كافية للنباتات؟

االخضرار Signup and view all the answers

ما هي الخاصية المميزة للساق الأجوف في القنبيط؟

تحتوي على فراغات هوائية Signup and view all the answers

أي من العوامل يُعتبر الأكثر تأثيرًا على جودة الساق الأجوف في القنبيط عند التخزين؟

وجود الأكسجين في البيئة التخزينية Signup and view all the answers

ما هو الدور الذي تلعبه الساق الأجوف في القنبيط بالنسبة للنبات؟

نقل العناصر الغذائية إلى الأوراق Signup and view all the answers

أي مما يلي يُعتبر تحديًا في عملية تصدير القنبيط بسبب خصائص الساق الأجوف؟

تعرض القنبيط للتلف بسهولة Signup and view all the answers

ما هي التأثيرات المحتملة لارتفاع درجات الحرارة على الساق الأجوف في القنبيط أثناء التخزين؟

زيادة نسبة البقع السوداء Signup and view all the answers

Study Notes

Post-Harvest Physiological Disorders in Horticultural Crops

These are not caused by living organisms, but by variations in the environment surrounding the fruits in the field and after harvest.
Poor nutrition and agricultural practices during growth, variations in atmospheric components, high ethylene levels around the fruit after harvest, and other non-disease factors contribute to these disorders.
Attention should be paid to the crop from the field, before harvest, during harvest, and ending with optimal storage conditions.

Temperature Injuries

Freezing Injury: Occurs when the crop is exposed to temperatures below its freezing point due to ice crystal formation within the intercellular spaces. This increased volume presses against cell walls causing damage, rapid deterioration, and tissue breakdown.
It also involves the loss of several compounds and can cause an unpleasant odour, as well as fungal diseases after the fruit is removed from storage.
Damaged fruit becomes very sensitive to mechanical damage during handling, transportation, and storage.
Symptoms include watery spots on the fruit or plant tissue, collapse, and damage to the outer and inner layers.
Vegetables vary in their sensitivity to freezing damage:
- Highly sensitive to freezing.
- Moderately sensitive to freezing.
- Less sensitive to freezing.
- Examples of crops:
  - Leafy greens (e.g., lettuce, spinach).
  - Root vegetables (e.g., carrots, beets).
  - Bulbs, tubers, etc.
  - Some fruits (e.g., apples, pears, stone fruits).
- The sensitive crops will have obvious damage with a single freezing event.
- Crops that can tolerate it have variable cold tolerance and can withstand multiple freezing events without damage.
To prevent freezing damage, store produce at a temperature above its freezing point by 0.5°C to 1°C. The storage temperature should always be above the crop's freezing point.

Chilling Injury

It occurs in cold-sensitive crops, particularly those of tropical or subtropical origin.
The condition manifests when placed at temperatures above the freezing point of water (0°C) and below the threshold temperature.
This threshold temperature is the temperature at which the crop should be stored to avoid cold damage, regardless of the storage period.
Cold damage is a physiological disorder with visible surface and internal symptoms, that do not show up during refrigerated storage, but develop quickly and become apparent shortly after refrigerated storage for a few hours to a couple of days, coinciding with market display. This leads to a decline in quality and decreased prices.
The following table provides safe storage temperatures for some cold-sensitive crops.

Crop	Safe Storage Temperature (°C)	Crop	Safe Storage Temperature (°C)
Pomegranate	5°C	Cantaloupe	5-3°C
Green beans	5°C	Zucchini	5°C
Ripe red tomatoes	10°C	Bananas	13-12°C
Cucumbers	7°C	Green peppers	7°C
Green chillies	7°C	Eggplants	7°C
Okra	7°C	Unripe tomatoes	13°C
Mangoes	14-12

Crop Factors Affecting Cold Sensitivity

Genetic factors: Legumes are generally sensitive to cold storage, while lettuce is an exception.
Maturity at harvest: The susceptibility of fruits to cold damage decreases as they approach maturity.
Fruit position on the plant: Fruits harvested from the outer periphery of trees are more susceptible than those from the interior.

Storage Factors Affecting Cold Sensitivity

Temperature: Cold damage symptoms do not emerge as long as the storage temperature is above the threshold temperature.
Reheating and acclimation: Repeated warming of fruits during refrigerated storage can significantly reduce their sensitivity to cold damage.
Relative humidity in storage: The sensitivity of fruits to cold damage decreases with increased relative humidity.
Modified or controlled atmosphere storage: Fruit sensitivity to cold damage decreases with high levels of carbon dioxide (in permissible limits).
Hot water treatment: Fruit treatment with hot water at temperatures from 45°C to 60°C for 3-5 minutes can reduce the sensitivity to cold damage.

Crop Postharvest Handling

Pre-storage calcium dip: Dipping fruits in calcium solution before storage helps reduce their sensitivity to cold damage.
Post-harvest preparation: Processes like dry cleaning, washing, or adding chemicals to the wash water can weaken fruit skins and increase cold-damage vulnerability.
Packaging and wax coatings: Both packaging and wax coatings can reduce fruit susceptibility.
Artificial ripening: Treatment with ethylene or ethrel reduces the sensitivity to cold damage.
Exposure to higher-than-critical temperature: Pre-cooling fruits to a temperature above the threshold for a few days can reduce sensitivity (e.g., exposing melons to 20-25°C for a few days before refrigeration at 5°C).

General Symptoms

Discoloration and ripening failure: Impairment of fruit ripening and discoloration of fruit in certain fruits like bananas, tomatoes, mangoes, and citrus fruits, due to reduced ethylene production or enzyme inhibition.
Pitting and spotting: Pits or spots appear near or under the fruit surface after refrigeration, may develop into watery areas prone to fungal infections. Common in stone fruit, cucumbers, zucchini, and bell peppers.
Internal breakdown: Affects fruit like citrus fruits (e.g., plums and apples), causing tissue discoloration, dryness, sourness, and water-soaked areas (particularly near the seed).
Watery breakdown: A condition affecting fruit like oranges, where the skin becomes spongy and watery, or in certain apples and Bartlett pears.
Increased susceptibility to microorganisms: Fruits often lose their ability to resist pathogenic microorganisms and become susceptible to fungal and bacterial infections.
Reduced palatability and nutritional value: A clear decrease in the flavour, taste, and nutritional quality of fruits.

Symptoms on Certain Fruits

Banana finger browning
Woolly appearance of some susceptible plum fruits
Vascular tissue malformation in custard apples
Pitting and pitting in peppers and cucumbers, and loss of shine in eggplants.

Causes of Chilling Damage

Reduced catalase activity (an antioxidant)
Respiratory abnormalities
Accumulation of toxic respiratory byproducts
Membrane damage
Reduced energy production and enzyme activity (especially respiratory enzymes).

Chilling Damage in Specific Crops

This section lists various crops and their associated chilling damage symptoms. Details are provided on each crop's specific reactions.

Heat Injuries

Exposure to high temperatures due to direct sunlight or elevated storage temperatures leads to significant quality and quantity losses.
Symptoms such as increased metabolic rate and reduced storage time, inhibition and failure of ripening (ripening failure), and poor fruit discoloration is evident in fruits like bananas and tomatoes.
Temperatures exceeding 40°C cause cell death.
Fruits lose firmness, deteriorate quickly, their respiration rates increase, stored compounds are lost, and they age prematurely.

Sunburns

Sun scald is the death, hardening, and whitening or yellowing of a part of the fruit exposed to high temperatures (42°C or more).
This leads to protein accumulation and cell death in the exposed part.
Fruit shrivel and wilt as a result of significant moisture loss due to high temperatures and low relative humidity.
Fruits lose their characteristic aromas due to the cessation of volatile gas production.
Fruits exhibit a cooked appearance, with browning of some skin areas.

Atmospheric Gases Physiological Disorders

Black heart in potatoes: Occurs due to low oxygen levels in storage.
Physiological damage from ethylene gas (previously discussed).

Nutritional Deficiencies (Nutritional Factors)

Calcium deficiency:
- Core rot in apples
- Brown speckles in pears
- Blossom-end rot (occurs with low transpiration rates and reduced calcium uptake; prevent with appropriate watering).
- Dark heart in cabbage
- Scorched tips in lettuce
Nitrogen deficiency/excess:
- Increased incidence of brown rot
- Increased moisture in onions and garlic with high nitrogen levels, delaying ripening and reducing storage life.
- Hollow heart and cracking in broccoli and cauliflower
- Increased incidence of soft rot in tomatoes.
Boron deficiency:
- Hollow stems in cauliflower.
- Other symptoms related to boron deficiency.

Environmental and Agricultural Practices

A list of environmental and agricultural practices related to physiological damage is provided. This includes sunburn, cracked fruit, "cat's eye" fruit, hollow fruit, irregular fruit coloration, secondary growth or cracking, greening, fruit deformities, cucumber and bean pod twisting, thick onion necks, planting methods, and others.

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يختبر هذا الاختبار معرفتك حول شروط تخزين المحاصيل الزراعية وتأثير درجات الحرارة على جودتها. ستتعرف على كيفية تجنب الأضرار التي قد تلحق بالمحاصيل عند تخزينها في درجات حرارة غير مناسبة. ما هي المخاطر المرتبطة بالتخزين غير السليم؟