lab report writing food chemistry

Bachelor of Food Technology (Honours)

FOOD CHEMISTRY 141.395

Laboratory Report Writing Guide

With thanks to Mark Downey

Massey University Singapore - Bachelor of Food Technology (Honours)

Topics

• Report writing examples

• Writing styles

• Tips to save time and improve grades


Grades (a rough guide)

Proximate Analysis (Prox 1 & 2)

FFAs/Gas Chromatography

Title 2 Title 2

Abstract 10 Abstract

Aim 5 Aim 8

Introduction 15 Introduction 15

Methods & Materials 5 Methods & Materials 5

Results 18 Results & Discussion 30

Discussion 20 Unknown sample 15

Conclusion 5 Conclusion 15

References + Appendices 5 Appendices 5

Writing Style 15 Writing Style 5


Title page & Abstract

Title• Enough detail to explain what the report is

about….but short and sweet in one sentence!• Date of submission (Mrs. Ser Wai Ming)• Paper title and number

Abstract

• Summarise briefly the aim of the experiment, methodology used and the results. Also, any significance or limitation!

• Do not exceed 200 or 250 words!


Aim

• Summarises the purpose of the experiment– What are you analysing?– Why?– How?

• Concise• The aim defines what will be in the conclusion, so it

must be specific but…• Can be incorporated into the introduction


Aim:

Example 11. To determine the sulphur dioxide content in various foods using the Monier-Williams method. The foods include: Dried apricot Sausage meat Grape Juice 2. To assess the accuracy of the current method by comparing with literature values. Example 2 The objective of this work was to measure the sulphur dioxide content in a range of food and drink (dried apricot, sausage meat and grape juice), using the well-known Monier-Williams method. To gain an idea of accuracy, the data was compared with literature values

Title & Aim examplesTitle:

The Sulphur dioxide content of Dried Apricot, Sausage and Grape Juice (good) The Sulphur dioxide content of various foods using the Monier-Williams method (ok) Sulphur Dioxide analysis of foods (poor)


Introduction

• The problem to be investigated and why it is important to be studied, supported by key literature references– Background scientific information– Measurement techniques– Topical issues

• Sufficient relevant theory and history about how the problem is measured, so that investigator could understand how it works (references are useful);

• The intended method of approach to measure the problem, and the expected results; and

• A brief statement of the aim of the experiment. It should be more informative than the title.


Introduction example

Sulphur dioxide is used in the food and drink industry to preserve food samples from microbial contamination that may spoil the food. It acts by blocking the metabolic pathway of most spoilage bacteria (reference). Concern has been expressed at allergic reactions in people sensitive to sulphur dioxide (ref). It is therefore important to know the level of sulphur dioxide in a food. These levels can vary considerably. For example, dried apricots contain over 1000 ppm SO2, but sausages contain only 450 ppm.

The SO2 content in foods can be determined using the Monier-Williams method (ref). The principle of the test is to convert the sulphite-containing compounds into sulphuric acid. Phosphoric acid and heat are used to liberate sulphur dioxide from the food. This is then reacted with hydrogen peroxide to form sulphuric acid. A standard titartion can then be used determine the equivalent sulphur dioxide content (ref to manual).


Materials and Methods

• Describe the experimental work carried out, in your own words. Identify key details.

• DO NOT REPEAT INSTRUCTIONS, but refer to relevant page numbers (manual), note any modifications, and any significant changes.

• Concisely as possible.

• Use diagrams if useful (e.g. experimental apparatus).


Method examples

The relevant method can be found in Ravindran (2008). Three foods were analysed using the standard method. Samples were titrated after 20 minutes. (Not enough)

The sulphur dioxide content was measured using the Monier-Williams method, described in Ravindran (2007). The apparatus is as shown in Figure 2. Grape-juice, dried apricot and sausage meat were analysed in duplicate. Food samples were minced before adding water, ethanol and 35% phosphoric acid. Food samples were heated for 20 minutes to allow both free and bound sulphur dioxide to liberate into the hydrogen peroxide solution. Solutions were titrated with 0.1M, rather than 0.01M sodium hydroxide to a yellow end-point. (Good detail)


Results and Observations

• Results must be presented in the form of tables or figures and expressed to the appropriate number of significant figures

• Always include a numerical estimate of the precision of your data (mean SD or SE)

• Include any relevant observations about the way the experiment went that may affect the results

• DO NOT add raw data, only key data that will be referred to in the Discussion.


Table example

Table 1: Average levels of sulphur dioxide in a selection of food and drink.

Food SO2 level (ppm) Standard deviation

Sausage meat 450 10

Dried apricots 1020 20

Grape juice 34 5

Table: Sulphur dioxide levels

SO2 level SD

Sausage meat 450.58 10.65

Dried apricots 1020.70 20.55

Grape juice 34.11 5.21

•Units

•Rounding

•Consistent significant figures

•Informative title

•All abbreviations explained


Table example

Table 1: Sulphur dioxide levels in a selection of food and drink.*

Food SO2 level (ppm)

Sausage meat 450 ± 10

Dried apricots 1020 ± 20

Grape juice 34 ± 5

•Units

•Rounding

•Consistent significant figures

•Informative title

•All abbreviations explained

*Mean ± SD


Graph example

• Axes labelled• Easy to present a

clear message

0

200

400

600

800

1000

1200

1400

SO

2 l

ev

el

(pp

m)

Figure 1: Individual determinations of sulphur dioxide content in various

food samples


Discussion

• The nature of the data collected is described

• Refer to the Tables and Figures presented in the Results section.

• Discuss significance of results to the objectives/aims you set out to achieve.

• Cite any theoretical arguments which support your position.

• Discuss reasons for inconsistencies and discrepancies in your data esp. with the literature. Give references.

• Conclusions and recommendations will be drawn from this section

• If several objectives, divide into numbered sections with headings


References• A full list of references cited in the text must be given.

• Provide references in a consistent style.

• ALL REPORTS MUST CITE RECENT AND RELEVANT JOURNAL ARTICLES.

– Articles (Google, Google scholar, Web of Science)– Books etc (Library catalogue)

• Examples of correct referencing technique are given in your study guide and in your manual.

• Should be enough detail so that article can be found from the reference given.


Writing Style• Use the PAST IMPERSONAL tense:

– In writing about anything performed, use past tense.

– When referring to things that exist within the report, the present tense can be used.

– Personal words such as “I”, “our” or “we” should NOT be used.• “Six measurements were made”

– Avoid starting references with verbs. Keep to the “passive voice” rather than the “active voice”. • For eg., “See Figure 1” should read “Figure 1

shows”. • For details, see Appendix 1” should read

“Further details are given in Appendix 1”.• Correct speeling!


Writing ExamplesThe measured levels of sulphur dioxide in sausage meat, dried apricots and grape juice are shown in Figure 1. The results show that dried apricots contained the highest level of sulphur dioxide of the three foods tested. The values for the three foods were confirmed by Russell and Gould (2003) to be accurate.

Benarde (1971) found that levels of sulphur dioxide above 500 ppm can be a risk to people who are sensitive to this preservative. In contrast, the minimum level of sulphur dioxide required to preserve sausage meat adequately is 400 ppm (Foulke, 1995).

There were unacceptable variations in the duplicate measurements of grape juice samples. On analysis of the experiment, two factors were identified. In one case, the sample container was not connected to the apparatus immediately after the acid was added. Fennema et al. (1996) claimed this may cause lower measured values than the true value. For the other sample, during the titration, the bottle appeared to be leaking. This was noticed after the laboratory was completed and could not be repeated. This would have given a larger titration value than was expected.


Conclusions & Recommendations

• Relate directly to the objectives detailed in the introduction and addressed in the results and discussion.

• Summarises what you have already said.

• State firmly the major conclusions.

• Recommendations suggest an action.

• Be specific.


Conclusion example

Conclusion:The sulphur dioxide content of dried apricot was found to be the highest at 1220 ± 90 ppm. Values of 440 ± 10 ppm and 34 ± 5 ppm were found for sausage meat and grape juice, respectively. These values were consistent with literature values. The precision was found to be below 10% for both the apricot and sausage meat samples, which are acceptable. However, the grape juice sample had a coefficient of variation of 15%. Low sulphur dioxide values are believed to affect the precision of the Monier-Williams method.

It is recommended to repeat the grape juice measurements with both the Monier-Williams method and an iodometric titration method, which is believed to be more accurate.


Appendices

• All raw data– amount of samples used, – individual results of replicates, – formula and calculation details.

• Formatting less important


Tips for Report Writing

• Perform the data analysis as soon as possible. It should be able to be used in your appendices.

• Note anything unusual or that you think will be useful in the discussion.

• Start the main report itself by writing the Introduction and Experimental sections first.

• The results you present, and the discussion, are chosen to meet the objectives in your Introduction.

• Ensure that all Tables and Figures are properly labelled with heading, title etc.

• Check that appropriate references to details in the Appendices are given.

• Finally write the conclusions and list of references.• PROOFREAD YOUR WORK and tidy up.


The most common report writing faults that downgrade marks are:

• Poor formatting of results sections• Missing information• Lab questions not answered • Introduction too short, methods & material

section too long• Muddled discussion • Reports that do not address the tasks set

– e.g. conclusion & aim inconsistent• Lack of specific detail


Plagiarism

• Copying or paraphrasing another person’s work, whether published or unpublished, without clearly acknowledging it, will be deemed to be dishonest and not acceptable.

• If you use the words of another author you must enclose

them in quotation marks. • You must cite a page number and the full reference in the

Reference List. • Plagiarism will be penalized which leads to loss of marks

for that item of assessment and may lead to an automatic failing grade for the paper and/or exclusion from enrolment at the University.

lab report writing food chemistry

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