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Best Practice for Literature Searching

For the sciences of food and health

Defining research questions

To run a successful literature search, you need to frame your question in a way that brings back relevant results.  

You need to identify the main components of your research question and think about how they intersect.

You might break your research question into separate parts to see what relevant research has been done on each for your literature review, so you might need to run multiple searches.  Or, you might be looking for all the research on a specific question so you might run a single search (in more than one place) for your review.

Thinking about how specific to make your question(s) is important—if you frame your question as a very broad query, you can be overwhelmed by results. On the other hand, if you frame your question too narrowly, you risk missing important information.

How to frame a question

Using a conceptual structure to frame your question helps you focus your search. In health fields, searchers often use the PICO framework.  PICO stands for Patient, Intervention, Comparator and Outcome.  Food science researchers can use a modified version of PICO to frame their search question.  Variations like PECO, PO, PIT, or PES (see chart below) can also be appropriate.  These structures help you identify what elements are key for your question.
 

Possible elements in your research question
P - subject product, population, animal, cells, food group, plant, chemical, environmental factor
I - intervention what is being tested - a process, a method, something else?
S - setting place, country, building, i.e. meat processing plant
O - outcome/result what is the result?  i.e. safety, quality, sustainability, etc.
C - comparator are you comparing with something else?
C - characteristic/property rheological, functional, chemical, sensory 
T - Timing for tests this may be useful
E - Exposure for example, to a disease or pathogen

Note: do not include all the possible elements in your research question--doing that would make your question too specific, and make it extremely unlikely you'd find relevant literature.

A good search question contains three elements, but sometimes two is better, and sometimes four. It's good to identify the elements of your search question, and then, when you are structuring your search, experiment with how many terms to actually use in your search string. For instance research is often interested in an outcome, but you might leave that element out of the actual search.

Example questions

Research question
What impact does ethylene production during ripening have on apple quality changes during storage?
P - subject product, population, animal, cells, food group, plant, chemical, environmental factor
apples
- intervention what is being tested - a process, a method, something else?
ethelyne/ripening
S - setting place, country, building, i.e. meat processing plant
storage
O - outcome/result what is the result?  i.e. safety, quality, sustainability, etc.
quality
- comparator are you comparing with something else?

C - characteristic/

property

rheological, functional, chemical, sensory 
- Timing for tests this may be useful
E - Exposure for example, to a disease or pathogen  
Research question
Can bacteriophages be used to prevent formation of Vibrio parahaemolyticus biofilms?
P - subject product, population, animal, cells, food group, plant, chemical, environmental factor
Vibrio parahaemolyticus biofilms
- intervention what is being tested - a process, a method, something else?
bacteriophages
S - setting place, country, building, i.e. meat processing plant
O - outcome/result what is the result?  i.e. safety, quality, sustainability, etc.
prevention
- comparator are you comparing with something else?

C - characteristic/

property

rheological, functional, chemical, sensory 
- Timing for tests this may be useful
E - Exposure for example, to a disease or pathogen
Research question
Does maternal diet impact risk of preterm birth
P - subject product, population, animal, cells, food group, plant, chemical, environmental factor
pregnant women
- intervention what is being tested - a process, a method, something else?
diet
S - setting place, country, building, i.e. meat processing plant
O - outcome/result what is the result?  i.e. safety, quality, sustainability, etc.
preterm birth
- comparator are you comparing with something else?

C - characteristic/

property

rheological, functional, chemical, sensory 
- Timing for tests this may be useful
E - Exposure for example, to a disease or pathogen  
Research question
What are appropriate methods for determining the allergenicity of novel foods?
P - subject product, population, animal, cells, food group, plant, chemical, environmental factor
novel foods
- intervention what is being tested - a process, a method, something else?
testing methods
S - setting place, country, building, i.e. meat processing plant
O - outcome/result what is the result?  i.e. safety, quality, sustainability, etc.

- comparator are you comparing with something else?
C - characteristic/ property rheological, functional, chemical, sensory 
allergenicity
- Timing for tests this may be useful
E - Exposure for example, to a disease or pathogen  

 

Downloadable template

Exclusions and Inclusions

When framing your research question, it is also good to think about your inclusion and exclusion criteria. Remember, however, that limits may introduce bias.

Examples what you may want to cover include:

  • Geographic area
  • Population group(s)
  • Types of studies
  • Language - If you only read English, remember that many databases translate titles and abstracts into English. This should give you enough information to judge if a study is relevant enough to have it translated in full into English.

Notice that limiting by date is not included on this list. As a rule, your literature review ought not to cover just the latest developments.  Sometimes critical research has been done decades ago and not repeated because researchers were aware of it. If you are new to a subject area, don’t make the mistake of overlooking seminal research.

Best practice!

Best practice recommendation: If you are looking at a recent development in research, you should also look back at the foundational, historical research that is key to understanding current research.