Sensory evaluation of juice blends

Nine blends (explained in Chapter 4) were narrowed down to four blends after initial screening. The four blends including BEET IT were subjected to sensory evaluation to investigate acceptability of flavour, acidity, sweetness and overall liking of the juice.

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The data analysed from this evaluation provided a final formulation for this project and was used for storage trial. The samples were organoleptically assessed by consumers

using sensory rating scales (Appendix B).

3.9.1 Sample preparation

All juices were made in the product development laboratory (Massey University,

Albany) as explained in Section 3.6. Blending of different juices was carried out one

day prior to sensory testing and samples were stored in 1 L HDPE at 4±1qC. In total,

four juices (results section) were produced. Strict hygiene and sensory practices were carried out to ensure the safety of the beverages produced. The samples were also tested in the microbiological laboratory for total aerobic counts and yeasts and moulds and ensured they were within the acceptable limits before conducting the sensory evaluation. Each panellist received 10 ml juice samples served in 60 ml clear plastic sample cups (Galantai Plastics Group Limited, Auckland, New Zealand) coded with a three digit random number. The plastic cups were labelled a day before and sealed in a 5L air tight plastic container to prevent dust, dirt from entering the cups. Chilly bins and

ice packs were used to maintain temperature below 4±1qC.

3.9.2 Testing location

Consumer testing was carried out in two locations- Auckland based gym (Club Physical, New Zealand) and Massey University sensory booths (Sensory laboratory, Massey, Albany) over two days. Two locations were chosen to ensure enough consumers were tested. Sensory evaluation was carried out just outside the gym but inside the building premises and an appropriate table was provided for the preparation

area. Juices were maintained at 4±1qC by storing the juices in chill bins containing ice

packs, hourly temperature checks were performed on the juice. The second testing of

the juice assessments were held under temperature controlled condition (20±1qC) in the

sensory booths at Massey University. The sensory booths were separate from preparation area to prevent the panellist from having physical or visual access to

information that may bias their response. The juice was served between 3 to 5qC in the

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3.9.3 Panels and participants

Sensory evaluation was completed by 70 consumers in total, 40 consumers at the gym and 30 consumers at Massey University tasting booths . Every panellist was given a

participation information form and a consent form to fill out (Appendix C). An ethics

approval was granted before commencing testing as attached in Appendix C. Sensory

testing was carried out over two days, from 9:00 am to 2:00pm at Massey University.

3.9.4 Presentation of samples

Five cups (60 ml), labelled with 3-digit random numbers were placed on the white

serving trays based on randomisation chart as attached in Appendix D. The juice

samples were presented following a complete block Williams Latin squared design, balanced and randomised for carry-over effects, to avoid artefacts due to presentation order and sensory adaptation due to continuous exposure (Lawless & Heymann, 1998).

Juice was served at 4±1qC directly from fridge or chilly bin as this represented the

beverage drinking temperature if purchased from a retail display unit. The consumer

sensory evaluation forms (Appendix B) were arranged according to the consumer

number and the randomisation chart. Appropriate stationary and serviettes were also

presented to the consumers in the tray to give the test. A glass of tap water (20±1qC)

was served with every tray and panellists were asked to rinse their mouths with water

between samples. Five samples (apple flavour high acid, orange flavour high acid,

apple flavour low acid, orange flavour low acid and BEET IT) per consumer were presented with the respective consumer sensory form under white lighting set up at the sensory booth at Massey and in daylight in the gym premises.

3.9.5 Sensory evaluation form structure

Consumer panellists were required to perform a simple test by using sensory scales commonly treated as interval scales. The scale was divided into intervals of equal size, labelled with descriptive term and numbers (Lawless & Heymann, 1998). Seven and nine point sensory scales were used in this study (Lawless & Heymann, 1998). Seven point scale was used to determine the liking for attributes such as sweetness, flavour and acidity liking whereas nine point scale was used to determine the overall product liking.

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Nine point scale was used for overall product liking because consumer responses are repeated more consistently and also the test discriminated between the items at nine point scale as compared to seven point scale (Lawless & Heymann, 1998). On the sensory scale, the numbers on the left hand side indicated the least liked attributes, whereas those on the right were most liked. Randomisation of samples helped in ordering samples such that each unit had an equal chance of being chosen at each stage of the ordering process. Consumers were asked to fill out their gender and select an age group to study the demographics within the consumer trial. From the analysis of consumer forms, 36 males and 34 females attended the consumer tasting aged between 20 to 60 years old.

3.9.6 Discrimination triangle sensory test

The sensory evaluation was conducted in the sensory laboratory at Massey University, Albany. Three coded samples were presented to each panellist, and each panellist was asked to pick out which sample they felt was different to the other two (Meilgaard et al, 1999). All six possible combinations of presentation were randomly presented to the panellists (AAB, ABA, BAA, BBA, BAB, ABB). Twenty-five consumers participated in the triangle test as recommended by Lawless & Heymann, 1998. Placebo and high

nitrate rich beverage were prepared and stored frozen (-20±1qC) for three days and

analysed for microbial and fungal counts prior to tasting. Random three digit codes

were used for samples. Three sample cups (two – same formulation, one-different

formulation) were presented to every panellist in a randomised order (Table in Appendix D). Panellists were asked to place at tick for the odd tasting beverage. It was advised to taste the samples from left to right and to drink water in between samples and before the test. Statistics was performed to test for significance using MINITAB 16.

More specific details about the consumer sensory evaluation are explained in Section

3.8.

3.9.7 Statistical analysis of sensory data

Microsoft Excel (2010) was used to calculate means, standard errors, standard deviations and graphically present the results. All the sensory data acquired from the consumer tasting evaluation was analysed statistically using MINITAB 16. The data

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was analysed statistically to test the hypotheses and to find any significant differences between samples and if they depend upon other variables. All other statistical data was derived by conducting t tests on MINITAB 16 and chi test on EXCEL 2010.

The normality of the population was tested using a Ryan-Joiner test. For this analysis, the following null hypothesis was tested:

The data {x1, x2,….,xn} are a random sample of size n from a normal distribution

Test statistic: RJ/r= the sample correction coefficient calculated from z percentile, observation) pairs where the z percentiles are for proportions (i-0.375/n+0.25) (Chantasorn, 2011).

In a Ryan Joiner test, if the data have a normal distribution, then the normal probability plot (plot of normal scored against the data) will be close to a straight line and the correlation r will be close to 1 (Chantasorn, 2011). If the data are sampled from a non- normal distribution then the plot may show a marked deviation from a straight line, resulting in a smaller correlation (r) (Kuo, 2001). Smaller values of r, are therefore regarded as stronger evidence against the null hypothesis (Kuo, 2001).

One way analysis of variance (ANOVA) was conducted on samples to determine whether there were any significant differences between the means of sample groups using p values. Any significance level (i.e. p value) of less than 0.05 indicated a significant difference between the mean of at least one pair of samples. As a result, the

null hypothesis (Ho) was rejected and the alternative hypothesis (Ha) was accepted. The

current hypothesis for the study is:

Null hypothesis (Ho): There is no significant difference among the samples

Alternative hypothesis (Ha): There is a significant difference among the samples

Analyses of Variance (ANOVA) for attributes were conducted using adjusted sum of squares (SS) for tests. Mean squares (MS) for the samples and error were calculated by dividing each SS by its representative degree of freedom (DF). The F values were compared to P value in order to determine whether there was any significant difference

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among the means for the treatment. The F values were determined by dividing the MS values by MS error.

Finally, Principal Components Analysis was conducted on overall product liking for all the samples using the MINITAB software explained in more details in Chapter 5.