Module 2: Minimally Processed Fruits and Vegetables

Question 1

What is the objective of preservation?

Answer 1

To control spoilage, promote safety, prevent waste, make food available year-round, and achieve economics.

Question 2

What are the controls used in preservation?

Answer 2

Water availability, temperature, level of acidity (pH level), and oxygen level.

Question 3

Name the techniques used for preservation.

Answer 3

Exclusion of air, removal of microorganisms, use of high temperature, use of low temperature, drying, use of chemical preservatives, and irradiation.

Question 4

What are minimal processed foods?

Answer 4

Products that maintain their attributes and quality similar to those of fresh products with a shelf-life of at least 4-7 days, preferably even longer, up to 21 days.

Question 5

List some examples of minimally processed fruits and vegetables

Answer 5

Vegetable sticks snacks, packaged toss salad, chilled peach halves, cored whole pineapple, shelled fresh legumes, freshly squeezed juices

Question 6

What is the objective of minimal processing?

Answer 6

To keep the produce fresh but convenient without losing its nutritional quality and to make the product shelf-life sufficient to make distribution feasible with a region of consumption.

Question 7

What is vacuum cooling?

Answer 7

A technique used for rapid cooling of crops by evacuating air which causes a rapid evaporation of water located on the surface of the crop.

Question 8

What is the hurdle technology?

Answer 8

It uses a combination of different preservation factors or techniques (“hurdles”) in order to achieve multi-target, mild but reliable preservation effects.

Question 9

What are the mechanisms by which hurdle technology affects microbial growth?

Answer 9

Homeostasis, metabolic exhaustion, stress reaction, and multi-target preservation

Question 10

What is homeostasis?

Answer 10

It is the tendency to uniformity or stability in the normal status (internal environment) of organisms, which is an important phenomenon in food preservation that interferes with the homeostasis of microorganisms to ensure that key physiological activities and parameters in the microorganisms remain relatively unperturbed.

Question 11

What is metabolic exhaustion?

Answer 11

It is the process where vegetative microorganisms completely use up their energy for repairing their homeostasis, become metabolically exhausted, and die.

Question 12

How does metabolic exhaustion cause “auto-sterilization” of food?

Answer 12

When microorganisms present in a food product overcome the hurdles present and enter the stationary phase, the microbial population decreases during storage as a result of auto-sterilization caused by metabolic exhaustion.

Question 13

What are the stages of the Microbial Growth Curve?

Answer 13

The stages of the Microbial Growth Curve are Lag phase, Exponential phase, Stationary phase, and Death phase.

Question 14

What are some examples of stresses that microorganisms can face?

Answer 14

Heat, pH, aw, ethanol, starvation, etc.

Question 15

What are stress shock proteins?

Answer 15

They are coping mechanisms produced by microorganisms to deal with stress.

Question 16

What happens if microorganisms receive simultaneous stresses at the same time?

Answer 16

If microorganisms receive simultaneous stresses at the same time, it becomes more difficult for them to cope, and some bacteria may become more resistant or virulent.

Question 17

Why is simultaneous exposure to different stresses energy-consuming for microorganisms?

Answer 17

Simultaneous exposure to different stresses will be energy consuming, as it will require the synthesis of several shock proteins, which can lead to metabolic exhaustion.

Question 18

What is multi-target preservation?

Answer 18

Multi-target preservation is the process of subjecting microorganisms to various sublethal stresses that act on various cell targets.

Question 19

How can a minimal, but most effective preservation of foods be accomplished?

Answer 19

A minimal, but most effective preservation of foods can be accomplished by selecting small hurdles with different targets.

Question 20

What are some potential hurdles for foods of animal or plant origin that might improve their stability and/or quality?

Answer 20

Temperature (high or low)
pH (low or high)
aw (low or high)
Competitive Flora (lactic acid bacteria, etc.)
Modified Atmosphere (carbon dioxide, oxygen, nitrogen, etc.)
Packaging (Vacuum packaging, active packaging, aseptic packaging, new edible coatings, etc.)
Radiation (UV, microwaves, irradiation, etc.)
Other Physical Processes (ohmic heating, high electric field pulses, radiofrequency energy, oscillating magnetic fields, photodynamic inactivation, ultrasonic, etc.)
Edible Film and Edible Coating

Question 21

What is the impact of acidification as a hurdle in food preservation?

Answer 21

Acidification with pH<4.5 can lead to non-germination of bacterial spores and reduces yeasts and molds.

Question 22

What is the impact of heat treatment as a hurdle in food preservation?

Answer 22

Heat treatment can lead to the inactivation of polyphenol oxidase and peroxidase enzymes, as well as the inactivation of vegetative forms of bacteria, yeasts, and molds.

Question 23

What is the impact of osmo-blanching as a hurdle in food preservation?

Answer 23

Osmo-blanching can lead to the inactivation of polyphenol oxidase and peroxidase enzymes.

Question 24

What is the impact of in-pack pasteurization (in combination with aw level of 0.93) as a hurdle in food preservation?

Answer 24

In-pack pasteurization (in combination with aw level of 0.93) can lead to the inactivation of vegetative forms of bacteria, yeasts, and molds.

Question 25

What is the impact of water activity (aw) reduction as a hurdle in food preservation?

Answer 25

It can help to prevent microbial growth and enzymatic activity, which can cause spoilage and reduce the shelf-life of food products. When the aw of a food product is reduced, the amount of free water available for microorganisms to grow and enzymes to act on the food substrate is limited, which can slow or halt these processes.

Question 26

What is the purpose of sulphitation using potassium metabisulfite?

Answer 26

It restricts browning during storage and has a marginal antimicrobial effect.

Question 27

What is modified atmosphere packaging?

Answer 27

It is a process that alters the gas surrounding a commodity to produce a composition different from that of air.

Question 28

What are the differences between modified atmosphere packaging and controlled atmosphere packaging or storage?

Answer 28

In modified atmosphere packaging, the atmosphere composition is maintained and controlled throughout storage and requires constant monitoring. It is used in transporting and storing selected post-harvest products. On the other hand, controlled atmosphere packaging or storage aims to prolong the shelf life of fruits and vegetables by controlling the levels of oxygen and carbon dioxide.

Question 29

How does temperature control affect microbial quality in modified atmosphere packaging?

Answer 29

It increases the inhibitory effect of MAP by increasing the solubility of CO2 in the liquid phase surrounding food, and decreases the growth rate of foodborne pathogens.

Question 30

What is the most low aw tolerant poisoning organism?

Answer 30

S. aureus.

Question 31

Why are fresh-cut fruit products much more perishable than their intact counterparts?

Answer 31

Physical injury triggers metabolic shifts, accelerates respiration, and induces wound ethylene production.

Question 32

What is the effect of cutting on fresh cut fruits and vegetables?

Answer 32

Cutting removes the natural protection of the epidermis and destroys internal compartmentalization that separates the enzymes from substrates, increases respiratory activity and ethylene emission, and causes physiological disorders.