practice question

Question 1

(iii) What are two (2) ways texture quality of carrots can be maintained over time? Briefly describe the biochemistry underpinning the prolonged shelf life carrots. [3 marks]

Answer 1

Controlled Atmosphere Storage: This method involves adjusting the levels of oxygen, carbon dioxide, and humidity in the storage environment. Lower oxygen and higher carbon dioxide concentrations slow down the respiration rate of the carrots, which reduces the rate of metabolic processes that lead to softening.

Refrigeration: Storing carrots at low temperatures (typically 0-4°C) slows down enzymatic activity, including the breakdown of starches and cell wall components. This helps maintain the crisp texture. At low temperatures, amylase activity (which converts starch into sugars) is reduced, preserving the starches in the carrots. Moreover, refrigeration slows the process of ethylene production, which is a plant hormone that accelerates ripening and softening.

Question 2

Food texture is perceived via the fingertips, lips, tongue, palate, teeth and jaw. Briefly explain the mechanism of textural perception at two (2) of these sites. [4 marks]

Answer 2

Fingertips: Rich in mechanoreceptors like Merkel cells (for pressure) and Pacinian corpuscles (for vibration), which detect firmness, roughness, and crunchiness of food when touched.

Tongue: Contains mechanoreceptors such as Ruffini endings (for pressure) and Meissner’s corpuscles (for light touch), which help assess softness, chewiness, and smoothness, as well as temperature and consistency during chewing.

These sensory receptors provide vital information about food texture, which is processed by the brain to form a complete sensory experience.

Question 3

Which samples are most likely to have been taken from a grass-fed system and which from a grain-fed system? Briefly explain the biochemistry underpinning the variation in colour from each production system [6 marks]

Answer 3

Grass-Fed: Darker red meat due to higher myoglobin content, more carotenoids in fat (yellowish fat).
Grain-Fed: Lighter red meat, less myoglobin, and white or pale yellow fat due to the energy-dense grain diet.
These differences in colour are mainly attributed to the animals’ diets, affecting the biochemical composition of the meat, including myoglobin levels and fat content

Question 4

Briefly describe how fat spoilage occurs in beef and two (2) strategies to reduce spoilage.

Answer 4

Fat spoilage in beef occurs mainly through oxidation, where oxygen reacts with unsaturated fats, leading to rancid compounds and off-flavors.

Two strategies to reduce spoilage are:

Modified Atmosphere Packaging (MAP): Replaces oxygen with gases like carbon dioxide and nitrogen, reducing oxidation.
Refrigeration/Freezing: Low temperatures slow down oxidation and enzyme activity, helping preserve fat quality.
These methods help maintain the freshness and extend the shelf life of beef.