To conduct a successful literature review, you need to conduct a comprehensive search so that you feel confident that you’ve found all the relevant literature on the topic you are investigating. You can put together an excellent search, but if you are not looking in the right places, you will not find the literature you need.
It is helpful to think about the tools you use in terms of whether they are better for accessing some research or if they are better for discovering all the research you need. Using search tools correctly will make all the difference in whether your search is actually comprehensive and systematic or not.
Access means getting the full text of research. Discovery means finding out about the existence of research. It is a very common mistake to use tools that are better for access for the task of discovery. Doing this means that you are doing your searching backwards!
The first step of your search must be discovery, and only after you know what is out there do you need to start acquiring the full text of the articles you need. Making this common mistake of reversing the order wastes time and negatively affects the quality of your literature review because you will be much less likely to find all the research you should be finding about your question.
The best tools for conducting your literature searches comprehensively and systematically are subject specific databases.
Databases abstract and index the content of academic journals from multiple publishers, and when appropriate other publication types such as trade journals, standards, reports, conference papers and patents. They are designed for discovery—i.e. finding out that a piece of research exists and giving you the bibliographic details you need to find that piece of research.
The difference between subject-specific databases and general databases
Databases can either be multidisciplinary or focused on a discipline like chemistry, or language and literature, or the sciences of food and health. The focus defines the database's scope--what information is included within it--and how you find that information.
A subject focused database is usually built around a thesaurus of subject terms based in its discipline. Because of their breadth of coverage, multidisciplinary databases don't have thesauri, and this means that they are far more likely to return what are called false hits, or noise, where the term you search is not used in the sense you need.
Sometimes even when a database does have a thesaurus but one focused on a different discipline than where your topic falls, you will still get false hits with a term. Information retrieval in the area of food is complex because of the broadness of the field. For example:
FSTA, focused on food science, not only doesn’t bring back supernatural false hits for spirits, it brings back many more relevant ones about distilled alcoholic beverages because of how each record has been tagged, or indexed, with the subject specific term spirits, even when that term does not appear in an article’s title or abstract.
What is indexing and why is it helpful in searching?
Databases that use a thesaurus, or controlled vocabulary, for indexing content, pull all the different terms referring to a topic together under a single heading. This helps users navigate the variations in language and terms used by researchers.
For example, in FSTA, if you search the thesaurus term aroma it pulls together all the results where the authors used the word aroma to describe a central element of the research, but also works by authors who used the words odor, odour or smell.
Similarly, research about Baijiu, Luzhou-flavor liquors, Luzhou-flavour liquors, Moutai liquors, and Moutai-flavor liquors are all gathered under the thesaurus subject heading Chinese liquors.
Some databases rely on machine learning to do the indexing, while others like FSTA have editorial teams of experts who do the work more accurately.
Search engines like Google allow you to find all sorts of information on the internet, but they are not designed specifically for finding scholarly information, so are terrible for literature searches.
However, they are good for finding governmental information like U.S. Department of Agriculture research funding instructions, scientific reports from the UK Food Standards Agency or the European Food Safety Authority, or guidelines from organizations like the World Health Organization. Academic search engines and most databases do not include this type of document. The database FSTA is an exception, since it indexes legislation, standards and reports (but not funding instructions).
Unlike general search engines, academic search engines like Google Scholar do focus on scholarly information, but they:
DO NOT allow precise control over searches, even with advanced search options.
Search engines can be useful for accessing the full text of articles and patents but using them for discovery is an inefficient--and potentially hazardous--way to research.
Platforms like Academia.edu and ResearchGate allow researchers to create profiles to showcase their work and share their articles. Both can be useful for acquiring full-text articles; however, because researchers create and maintain their own profiles, searching these platforms will not give you a comprehensive overview of a field—you’ll only find the work of researchers who have chosen to participate.
Don’t confuse these platforms with discovery services, such as databases, which are specifically designed to be comprehensive in the subject area they cover in order to help researchers find relevant information.
Some tools might seem to be full text databases but are actually publisher-specific platforms. ScienceDirect, the subscription platform hosting Elsevier’s journal articles, is a notable example. ScienceDirect makes it very easy to access Elsevier content, but only about 20% of food science research is published in Elsevier journals. Using that platform or any other single publisher platform to search for content will drastically limit your search.
Library discovery services are designed for discovery and access. They are intended to make it easy for a user to search in one place to find everything in the library's collections-print and e-books, articles, and more. They make it easy to access the full text of everything they own or subscribe to, or link to inter-library loan forms to borrow material from other libraries. The disadvantages of using them for the discovery process are that:
BEST PRACTICE RECOMMENDATION: Look at the library discovery page for a link to the subject specific databases. You can often see a list ordered by subjects or alphabetically or both.
BEST PRACTICE RECOMMENDATION: familiarise yourself with the databases you have access to, including subscription databases –get to know their scope (what content they index) and also how to search them, including using thesaurus functions if available, so that you can use each to their full capacity.
BEST PRACTICE RECOMMENDATION: remember that research for a literature review is a two-step process—first is discovery of research, and the second is accessing the research you’ve determined you need. Don’t switch the order of the steps! If you limit your search to the research outputs that you think that you have easy access to, you will almost certainly end up with a biased review that is neither systematic nor comprehensive.