Postharvest Technology and Food Preservation MCQs 2026

Which postharvest process remains active in fruits and vegetables after harvest and consumes stored sugars?

1. A Respiration ✓
2. B Photoperiodism ✓
3. C Vernalization ✓
4. D Seed dormancy ✓

A climacteric fruit is best described as a fruit that shows:

1. A No respiration after harvest ✓
2. B A respiratory peak accompanied by increased ethylene during ripening ✓
3. C Ripening only while attached to the plant ✓
4. D Complete immunity to chilling injury ✓

The main purpose of pre-cooling freshly harvested produce is to:

1. A Increase starch accumulation after harvest ✓
2. B Sterilize the surface of produce ✓
3. C Remove field heat rapidly before storage or transport ✓
4. D Convert non-climacteric fruit into climacteric fruit ✓

Which operation should normally be done before loading perishable vegetables into refrigerated transport?

1. A Sun drying ✓
2. B Fermentation ✓
3. C Wax crystallization ✓
4. D Pre-cooling ✓

The most widely used method to slow respiration and senescence in fresh produce is:

1. A Low temperature storage ✓
2. B Exposure to direct sunlight ✓
3. C Increasing oxygen to pure oxygen ✓
4. D Rough mechanical handling ✓

In cold storage of leafy vegetables, high relative humidity is maintained mainly to reduce:

1. A Protein synthesis ✓
2. B Transpiration and wilting ✓
3. C Ethylene biosynthesis only ✓
4. D Seed germination ✓

The availability of water for microbial growth in a food is expressed as:

1. A Moisture percentage only ✓
2. B Relative density ✓
3. C Water activity ✓
4. D Thermal diffusivity ✓

Blanching before freezing vegetables is primarily done to:

1. A Increase pesticide residues ✓
2. B Raise water activity ✓
3. C Remove all bacterial spores ✓
4. D Inactivate enzymes that cause quality deterioration ✓

Commercial sterilization in low-acid canned foods is designed especially to control spores of:

1. A Clostridium botulinum ✓
2. B Lactobacillus plantarum ✓
3. C Saccharomyces cerevisiae ✓
4. D Aspergillus niger ✓

The pH value commonly used to separate low-acid foods from acid foods in canning is:

1. A 2.0 ✓
2. B 4.6 ✓
3. C 7.5 ✓
4. D 9.0 ✓

Pasteurization differs from sterilization because pasteurization:

1. A Always produces a completely sterile product ✓
2. B Is applied only to dry grains ✓
3. C Reduces pathogens and spoilage organisms but does not destroy all spores ✓
4. D Requires freezing temperatures ✓

Drying preserves foods mainly by:

1. A Increasing enzymatic browning ✓
2. B Increasing oxygen solubility ✓
3. C Converting sugars into proteins ✓
4. D Lowering water activity below the level needed by many microbes ✓

Controlled atmosphere storage differs from ordinary cold storage by regulating:

1. A Oxygen and carbon dioxide concentrations ✓
2. B Only carton size ✓
3. C Only light intensity ✓
4. D Only wax thickness ✓

Modified atmosphere packaging of fresh produce depends on the balance between film permeability and:

1. A Seed viability ✓
2. B Produce respiration rate ✓
3. C Soil salinity ✓
4. D Can seam thickness ✓

Potassium permanganate sachets are used in produce storage mainly to absorb:

1. A Carbon monoxide ✓
2. B Starch ✓
3. C Ethylene ✓
4. D Calcium ions ✓

Chilling injury in tropical fruits occurs when produce is held:

1. A Only after complete freezing ✓
2. B Only at room temperature ✓
3. C Only in dry grain storage ✓
4. D At low temperatures above its freezing point but below its tolerance limit ✓

A reliable harvest maturity decision for many fruits usually combines:

1. A Size, color, firmness, soluble solids and days from bloom ✓
2. B Only fertilizer brand ✓
3. C Only storage room height ✓
4. D Only truck engine power ✓

Hydrocooling removes field heat by using:

1. A Hot air ✓
2. B Chilled water ✓
3. C Dry salt ✓
4. D Infrared light only ✓

Forced-air cooling is effective because it:

1. A Relies only on natural room air movement ✓
2. B Uses boiling water for cooling ✓
3. C Pulls or pushes cold air through packed produce using a pressure difference ✓
4. D Requires airtight metal cans ✓

Waxing citrus and some fruits is mainly intended to:

1. A Increase respiration rate ✓
2. B Destroy all viruses inside fruit ✓
3. C Remove soluble solids ✓
4. D Reduce moisture loss and improve appearance ✓

Hurdle technology means preservation by:

1. A Combining several mild preservation factors to inhibit spoilage ✓
2. B Using a single severe heat treatment only ✓
3. C Avoiding all packaging ✓
4. D Storing food only in sunlight ✓

Osmotic dehydration removes water from fruit pieces by placing them in:

1. A Distilled water only ✓
2. B Concentrated sugar or salt solution ✓
3. C Neutral cooking oil only ✓
4. D Dry nitrogen gas only ✓

Sulfur dioxide is used in some dried fruits mainly to:

1. A Increase insect egg hatch ✓
2. B Increase water activity ✓
3. C Control browning and inhibit microbes ✓
4. D Convert acids into alcohol ✓

Vacuum packaging extends shelf life of many foods by:

1. A Adding soil microbes ✓
2. B Increasing bruising ✓
3. C Increasing light transmission only ✓
4. D Reducing oxygen exposure ✓

Aseptic packaging means filling:

1. A A commercially sterile product into a sterile container under sterile conditions ✓
2. B Raw produce into unclean sacks ✓
3. C Frozen food into wet cartons ✓
4. D Dry grain into open baskets ✓

Freezer burn in frozen foods is mainly caused by:

1. A Excessive sugar fermentation ✓
2. B Surface dehydration due to ice sublimation ✓
3. C Anaerobic respiration in cans ✓
4. D Too much calcium in brine ✓

Individual quick freezing is preferred for peas and berries because it:

1. A Requires no low temperature ✓
2. B Raises product pH above 9 ✓
3. C Freezes small units rapidly and keeps pieces separate ✓
4. D Depends on insect infestation ✓

Refrigeration preserves perishable foods because it:

1. A Destroys every bacterial spore ✓
2. B Makes food completely dry ✓
3. C Stops all chemical reactions permanently ✓
4. D Slows microbial growth and biochemical reactions ✓

Benzoates and sorbates are most effective as preservatives in:

1. A Acidic foods ✓
2. B Highly alkaline foods ✓
3. C Pure fats only ✓
4. D Sterile dry salt only ✓

Nitrite is added to cured meat partly because it inhibits:

1. A Mango ripening ✓
2. B Clostridium botulinum ✓
3. C Polyphenol oxidase in apples only ✓
4. D Wheat sprouting ✓

Food irradiation preserves food mainly by damaging microbial:

1. A Cellulose in packaging ✓
2. B Table salt crystals ✓
3. C DNA ✓
4. D Metal can seams ✓

The purpose of HACCP in food processing is to:

1. A Replace all sanitation practices ✓
2. B Guarantee higher crop yield ✓
3. C Measure only fruit sweetness ✓
4. D Identify, evaluate and control significant food safety hazards ✓

In HACCP, a critical control point is a step where control can be applied to:

1. A Prevent, eliminate or reduce a hazard to an acceptable level ✓
2. B Increase marketing claims only ✓
3. C Change the brand name of a product ✓
4. D Make packaging heavier ✓

Bulging in a canned food container most commonly warns of:

1. A Perfect vacuum formation ✓
2. B Gas production from spoilage and possible safety risk ✓
3. C Ideal blanching ✓
4. D Low moisture in the can ✓

Headspace in a sealed can is provided primarily to:

1. A Promote insect growth ✓
2. B Keep the lid permanently loose ✓
3. C Allow product expansion and help form a vacuum after cooling ✓
4. D Increase oxygen for microbes ✓

Exhausting during canning is the operation that:

1. A Adds oxygen to encourage molds ✓
2. B Freezes the can contents ✓
3. C Increases field heat in vegetables ✓
4. D Removes air from the filled container before final sealing ✓

Retort processing of canned foods applies:

1. A Heat under pressure ✓
2. B Only ultraviolet light at room temperature ✓
3. C Only dry salt without heat ✓
4. D Only vacuum cooling ✓

The F0 value in thermal processing expresses:

1. A Percentage of fruit color ✓
2. B Equivalent lethality at 121.1 degrees C ✓
3. C Water activity of dried food ✓
4. D Amount of wax on peel ✓

Antioxidants are added to fat-rich foods mainly to delay:

1. A Yeast budding only ✓
2. B Seed germination ✓
3. C Oxidative rancidity ✓
4. D Can seam soldering ✓

The Maillard reaction is a type of:

1. A Cold-chain refrigeration ✓
2. B Respiratory cooling ✓
3. C Microbial sterilization only ✓
4. D Non-enzymatic browning ✓

Enzymatic browning in cut apple tissue is mainly associated with:

1. A Polyphenol oxidase activity ✓
2. B Nitrogen fixation ✓
3. C Botulinum toxin formation only ✓
4. D Starch gelatinization ✓

Ascorbic acid helps prevent browning in cut fruits because it acts as:

1. A A strong alkaline detergent ✓
2. B A reducing anti-browning agent ✓
3. C A source of insect larvae ✓
4. D A can seam lubricant ✓

Glass transition temperature is important in dried foods because it affects:

1. A Ethylene absorption by leaves only ✓
2. B Retort pressure gauge size ✓
3. C Stickiness, caking and physical stability ✓
4. D Seed pollination ✓

A key property of packaging film for fresh produce is its:

1. A Ability to generate soil nutrients ✓
2. B Ability to increase bruising ✓
3. C Complete opacity to all gases in every case ✓
4. D Permeability to gases and water vapor ✓

Modified atmosphere packaging for fresh produce must avoid extremely low oxygen because it may cause:

1. A Anaerobic respiration and off-flavors ✓
2. B Faster photosynthesis after harvest ✓
3. C Complete enzyme sterilization ✓
4. D Permanent freezing at room temperature ✓

A cold chain is best defined as:

1. A Only a single freezer in a market ✓
2. B Continuous temperature control from harvest or processing to consumption ✓
3. C A method of increasing field heat ✓
4. D A seed certification rule ✓

Sorting and grading after harvest help reduce losses mainly by:

1. A Increasing bruising intentionally ✓
2. B Stopping all respiration permanently ✓
3. C Removing damaged, diseased or unsuitable produce from the lot ✓
4. D Raising storage temperature ✓

Mechanical injury to fresh produce usually increases:

1. A Natural wax synthesis only ✓
2. B Seed dormancy only ✓
3. C Commercial sterility ✓
4. D Respiration, water loss and decay susceptibility ✓

Good sanitation in a packinghouse is important because it:

1. A Reduces postharvest disease inoculum on surfaces and equipment ✓
2. B Raises fruit temperature deliberately ✓
3. C Replaces all packaging needs ✓
4. D Eliminates the need for maturity indices ✓

Total soluble solids of fruit juice are commonly estimated using:

1. A A soil auger ✓
2. B A refractometer reading in degrees Brix ✓
3. C A pressure retort only ✓
4. D A seed drill ✓