Week 5 : Alchemy in the kitchen pt 2

Question 1

What is food processing?

(what 3 aspects does food processing entail)

Answer 1

Use of physical, chemical or biological means to convert raw food materials into consumable food products

Question 2

What are the 3 effects of food processing on food?

Answer 2

1. Microbial activity
2. Nutritive value
3. Sensory quality

Question 3

What is the main goal of food processing ?

Answer 3

To extend shelf life on food

Question 4

Food processing always leads to desirable sensory quality. True or False?

Answer 4

False

Question 5

Under what kind of condition will there be a large, detectable change in sensory quality in processed foods?

Answer 5

High heat

Question 6

Pastuerisation :

1. Is a mild heat treatment
2. is able to kill all microbes

Are the above statements True or False?

Answer 6

1. True, though it is heated to temperatures like 60-70+°C, it is considered mild heat since it is below 100°C
2. False, it can inactivate a wide range of spoilage organisms / pathogens but cant totally kill all of them

Question 7

What is the benefit of food processing on microbial activity of food?

Answer 7

Food processing involves heat, which reduces microbial growth in food (heat, causing reduction in water activity, add of chemicals etc) or totally kills all microbes

Question 8

What 2 aspects define the shelf life of foods?

Answer 8

Microbial activity and sensory quality

Sensory quality : e.g. potato chips go stale or “laohong” –> can reduce shelf-life of foods since it is undesirable to consumers and people are not likely to eat stale chips

Question 9

[Nutritive value]
Processed foods may be desirable as they enhance nutritive value of food. Explain how processing can enhance nutritional quality of food. [2]

Answer 9

1. Processed foods offer increased digestibility.
   - especially for protein : with heat in processing, partially denatured and 3D structure unwinds, enzyme can clave bonds more easily as they are more exposed.

(denaturation of protein not linked to bioavialbility bc techincally the proteins are available for utilisation)

2. Processed foods increase the bioavailability of nutrients (how much nutrients is available for body to utilise) –> cell walls of plant materials may have anti-nutritive factors which binds to minerals etc –> in processing, nutrients are released due to the destruction of cell walls

another minor point i thought of : fortification in processing –> increases nutritional quality

Question 10

However, there has been a debate that processed foods decrease the nutritive value of food. Explain how [2]

Answer 10

1. Processed foods cause the loss of certain nutrients
   - e.g. heat is often used in processing, and in processes like blanching, heat sensitive, water-soluble vitamins escape into the surrounding water.
2. Processed foods may generate toxicants harmful to our health

Another minor point i thought of inspired by FST2102B
- decreases bioavailability of nutrients, such as essential AA as they react with reducing sugars in the Maillard reaction

Question 11

Minimally processed or unprocessed foods (“natural foods”) may always not be nutritious / safe as they may naturally contain toxicants. List the 3 types of toxicants.

Answer 11

1. Natural foods, especially plant materials, have anti-nutritive factors (“plant toxins”)
   - e.g. phytate is a mineral chelator which decreases bioavailability of nutrients
2. Cyanogenic compounds (cyanides are toxic)
   - e.g. cassava
3. Mycotoxins, which are toxins produced by moulds in grains

Question 12

Acrylamide is a carcinogenic (cancer-causing) compound that is present in what kind of food?

The amino acid, Asparagine, is converted into acrylamide when cooked. What kind of reaction is this?

Answer 12

Fried, baked, roasted starchy foods (chao tar)

Maillard reaction–> heat involved + amino acid turn into amide (must have reacted w carbonyl)

Question 14

What kind of toxicants can be generated from smoking or barbequing food?

Answer 14

Polycyclic aromatic hydrocarbons (PAH)

Question 15

Heterocyclic amines (HCA) are carcinogenic compounds from cooking what foods?

Answer 15

Cooking muscle meats like beef, pork, fowl (chicken fish) at high temperatures

(Maillard reaction between amino acids and creatine)

Question 16

Not a question but main idea :

toxicants from food processing is mainly due to Maillard reaction of sugars and amino acids occurring at high temperatures and long periods of time

• Acrylamide
• Polycylic Aromatic Hydrocarbons (PAH)
• Heterocyclic Amines (HCA)

Answer 16

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