chemistry

Methional

Methional is a chemistry topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Methional rather than just read about it. In short: Methional is an organic compound with the formula CH3SCH2CH2CHO. It is a colorless liquid with an odour described as "musty, potato, tomato, earthy, vegetable, creamy, oily" that is a degradation product of methionine.

Key takeaways

Methional belongs to chemistry; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Methional to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Methional from memory before moving on to harder problems.

Reference excerpt

Methional is an organic compound with the formula CH3SCH2CH2CHO. It is a colorless liquid with an odour described as "musty, potato, tomato, earthy, vegetable, creamy, oily" that is a degradation product of methionine. It is a notable flavor in potato-based snacks, namely potato chips, one of the most popular foods containing methional. Traces of the compound can also be found in black tea and green tea based products. Methional contains both aldehyde and thioether functional groups. It is readily soluble in alcohol solvents, including propylene glycol and dipropylene glycol.

Occurrence In nature, methional is a thermally-induced volatile flavor compound. For instance, the heat-initiated Maillard reaction of reducing sugars and amino acids forms the initial basis of methional's composition. The formation of methional stems from the interaction of α-dicarbonyl compounds (intermediate products in the Maillard reaction) with methionine (Met) by the Strecker degradation reaction:

CH3SCH2CH2(NH2)CHCO2H + O → CH3SCH2CH2(HN=)CCO2H + H2O CH3SCH2CH2(HN=)CCO2H + H2O → CH3SCH2CH2CHO + NH3 + CO2 Methional easily degrades into methanethiol, which then oxidizes into dimethyl disulfide. Dimethyl disulfide is partly responsible for the "reactive sulfur" that contributes to the taste of potatoes. Furthermore, the methionine resulting from the Strecker degradation reaction produces alkyl pyrazines, which contribute to the flavors in roasted, toasted, or thermally processed foods. Due to the ease of its decomposition, a large portion of methional is lost during potato processing. Similarly, in the presence of flavin mononucleotide (FMN) and light, methionine is nonenzymatically oxidized into methional, ammonia, and carbon dioxide.

CH3SCH2CH2(NH2)CHCO2H → CH3SCH2CH2CHO + NH3 + CO2

Preparation and reactions Methional is synthesized commercially by the reaction of methanethiol and acrolein.

CH3SH + CH2=CHCHO → CH3SCH2CH2CHO Using the Strecker synthesis, methional is converted to methionine. For the purpose of animal feed supplements, enantiopure methionine is not required. Methional is a versatile reagent in organic chemistry.

Biological routes Because of their high cost, methional or its precursor methionine are not added during potato processing. In order to intensify flavoring of heat-processed potato foods, biotechnological approaches are used to increase methionine levels, and thus methional levels, in potato foods. The enzyme aminotransferase acts on methionine to remove the amine and form an α-keto-γ-methylthiobutyric acid. As catalyzed by α-keto acid decarboxylase, this ketomethylthiobutyric acid converts to methional.

CH3S(CH2)2CH(NH2)CO2H + O → CH3S(CH2)2COCO2H + NH3 CH3S(CH2)2COCO2H → CH3S(CH2)2CHO + CO2

References

Illustrations

Worked examples

Example 1 — a first encounter with Methional

Start with the simplest possible case. Write down what Methional claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In chemistry, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Methional before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Methional ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Methional

In research: Methional appears in chemistry research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Methional in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Methional is common in secondary-school and first-year university syllabi. It links to neighbouring topics Aldehydes, Flavors, Methylthio compounds, so understanding it makes those chapters shorter.
In everyday life: Look for Methional outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Methional in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Methional means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Methional out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Methional in simple terms?

Why does Methional matter?

Because it connects several chemistry ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Methional?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Methional.