“Entrevista anónima a los padres”

7.3.1 Methods

The experiments for screening spices were divided into two parts. Firstly, an investigation was made to preliminarily determine the responses of the panelists to the flavour and aroma of meatballs, with a number of spices. Based on the results obtained from this investigation, a Plackett and Burman experiment was used to screen for suitable spices.

The basic formulation for the meatballs was 75% mutton (trimmed product from 90% chemically lean meat), 20% pork and 5% pork fat, with 4% tapioca starch, 3% salt, 0.3% sodium tripolyphosphate. This was u sed for both the preliminary investigation and the Plackett and Burman experiment.

The meatballs were made by using the materials and ingredients described previously (refer also to Section 4.1 . 1 ) and the methods given in Chapter 4 (Section 4. 1 .2). Ice (20%) was added during chopping. The meatball samples were prepared for serving by deep frying in soybean oil at 200 ± 5 Co for two minutes since it was expected that cooking oil wou ld help enhance flavour and aroma of spices in the meatballs.

The e ight Thai panelists were asked to evaluate two characteristics of the s a mples : desirable flavour and aroma and undesirable flavour and aroma (see Figure 7.1 ) .

Desirable flavour and aroma

o extremely lacking desirable flavour and aroma

Undesirable flavour and aroma

o extremely having undesirable flavour and aroma 5 5

Figure 7. 1 Scales used for screening of spices

1 0 extremely having desirable flavour and aroma 1 0 extremely lackin g u ndesirable flavour and aroma

The q uestionnaire included only two questions so that it wou ld be convenient f o r the panelists to express their impressions of the samples, i.e. there were not too m any characteristics to assess. 'Muttoniness' was not directly used as a descriptive term to be assessed by the panelists. Instead, 'undesirable flavour and aroma' was used. This was due to the presumption that the panelists would have been prejudiced in assessing odour and flavour if they had been told beforehand about muttoniness.

Cooper et al. (1 988) stated that a score of zero for the ideal caused particular problem s in calculating the ideal ratio score since the ratio of product's score to the ideal score would be infinity. Due to this reason, the descriptions at both ends of the undesirable flavou r and aroma scale were reversed when compared to those of the desirable flavour and aroma scale, that 1 0 was extremely lacking undesirable flavour and aroma, 0 was extremely h aving undesirable flavour and aroma.

In the preliminary investigation, the panelists were asked to test the meatball samples and give their ideal absolute scores for each sensory characteristic. The mean ideal absolute scores for the two characteristics were later used in the Plackett and Burman experiment. Concu rrently , the panelists also showed their perceptions of the flavour and aroma of the meatballs by giving the product's scores for the two characteristics.

In the Plackett and Burman experiment, the vertical line of the mean ideal abso lute score was marked on each line scale (see Appendix 7.2) . The panelists were asked to evaluate the meatball samples and give the product's scores comparing them with the fixe d ideal absolute scores given.

Spices in this experiment were white pepper (0 .75%) . garlic (0.75%) , onion ( 0 .5%) , coriander (0 .375%) , fennel (0.375%) and sesame oil (0.3%) . The mean ideal abso lute scores for desirable flavour and aroma and undesirable flavour and aroma were 8.4 a nd 8.0 respectively. The mean ideal ratio scores (product score:ideal absolute score) for desirable flavour and aroma (0.87) and undesirable flavour and aroma (0.80) were below the ideal

ratio score (1 .0).

Therefore, it was expected that increasing the percentages of these spices wou ld i mp rove flavour and aroma. However, since there were comments by some pane lists t h at the meatball samples were too hot, the white pepper was maintained at 0 .75% ; and b ecause garlic has a very strong odour and flavour, it was maintained at 0 .75%. H owever, the percentages of onion, coriander, fennel and sesame oil were slightly raised to 0.6%, 0 .4%, 0.4% and 0.5% respectively. Therefore, the percentages of the six spices were set at their high levels at 0.75%, 0.75%, 0.6%, 0.4%, 0.4% and 0.5% for white pepper, garlic, o nion, coriander, fennel and sesame oil respectively. The low levels were set by reducing all the high values by one half. These low and high values of six spices were used in the Plackett and Burman experiment.

7.3.3 Plackett and Burman

There were eight experimental runs to study the effects of the six spices o n f lavour and aroma of meatballs as shown in Table 7. 1 .

Table 7 . 1 Combinations of spices i n a Plackett and Burman experiment to study their effects on flavour and aroma of mutton-based meatballs

Run No.(or Level of Each Ingredient(1 )

Treatment) White Garlic Onion Coriander Fennel Sesame Dummy

Pepper Oil 1 0.750(+) 0.750(+) 0.6(+) 0.2(-) 0.4(+) 0.25(-) (-) 2 0.750(+) 0.750(+) 0.3(-) 0.4(+) 0.2(-) 0.25(-) (+) 3 0.750(+) 0.375(-) 0.6(+) 0.2(-) 0.2(-) 0.50(+) (+) 4 0.375(-) 0.750(+) 0.3(-) 0.2(-) 0.4(+) 0.50(+) (+) 5 0.750(+) 0.375(-) 0.3(-) 0 .4(+) 0.4(+) 0.50(+) (-) 6 0.375(-) 0.375(-) 0.6(+) 0.4(+) 0.4(+) 0.25(-) (+) 7 0.375(-) 0.750(+) 0.6(+) 0.4(+) 0.2(-) 0.50(+)

₍

-

( 1 ) The percentage of each ingredient was based o n the total weight of meats (75% mutton lean and 20% pork lean) and fat (5% pork fat) .

The mean ideal ratio scores of desirable flavour and aroma and undesirable flavou r and aroma are given in Table 7.2.

Characteristic Treatment(2) Desirable flavour and aroma 0.85 ± 0.04 Undesirable 0.82 ± 0.03 flavour and aroma 2 0.84 ± 0.01 0.79 ± 0.03 3 4 5 0.83 ± 0.02 0.78 ± 0.02 0.76 ± 0.03 0.82 ± 0.02 0.78 ± 0.01 0.68 ± 0.02

(1 ) The scores were given by eight Thai paneiists. All means were not significantly different at p s; 0.05.

(2) Refer to Table 7.1 for treatment formulation.

6 7 8 0 .80 ± 0.02 0.79 ± 0.01 0.77 ± 0.00 0.77 ± 0.01 0.77 ± 0.03 0.76 ± 0.04 ... ... o

There was a tendency that the meatballs with high levels of white pepper, garliC and o nion had ideal ratio scores closer to the ideal of 1 , especially treatment 1 with white pepper, garlic and onion all at their high levels.

The mean ideal ratio scores of the desirable flavour and aroma and u ndesirable flavou r and aroma of the meatballs were then subjected to a Plackett and Burman design analysis. Every Plackett and Burman design includes, for each variable, the same number of runs at the high level and the low level. To calculate the effect of any input variable, one subtracts the average result at the low level of that variable from the average result at the high l evel of the same variable.

With eight runs or formulations, the effect of white pepper was calculated as (refer to Table 7.1 ) :

Effect (white pepper) = [1 + 2 + 3 + 5]

4

where 1 = value of the output variable in run or formulation 1 and so on.

[4 + 6 + 7 + 8)

4

Similar calculations were repeated for each of the effects including that of the dummy variable. The dummy effect was used to estimate the variance of an effect.

where Veff = variance of an effect

Ed = effect shown by a dummy

n = number of dummy variables, i.e. 1 in this experiment.

The standard error of an effect was calculated as

The significance of each effect was determined by using the t-test. Effect

S.E.eff

The calcu lated t-valu e was then compared with the tabu lated value whose degre e of freedom was equal to the number of dummy effects making up the error term. I n this

experiment, the levels of significance used were > 50%. This was due to the reason that only a rough screening was needed to compare the effect of each ingredient on flavour and aroma of the meatballs.

The results are presented in Table 7.3.

Table 7.3 Main effects of spices o n flavour and aroma of meatballs in the Plackett and Burman experiment Characteristic Desirable flavour and aroma main effect t-test significance level Undesirable flavour and aroma main effect t-test sig·nificance level White Pepper 0.035 1 .750 60% 0.01 0.33 n.s. Garlic 0.025 1 .250 50% 0.035 1 .1 70 50% Onion Coriander 0.03 1 .50 60% 0.04 1 .33 50% -0.01 -0.50 n.s. -0.045 -1 .500 60% Fennel S e same Oil -0.01 -0.025 -0.50 -1 . 2 50 n.s. 50% -0.01 5 -0. 0 2 -0.830 -0.67 n.s. n.s.

None of the spices had highly significant effects o n desirable f lavour and aroma and undesirable f lavour and aroma of the meatballs. However, it appeared that white pepper, garlic and onion slightly improved the flavour and aroma of the mutton-based meatballs whereas coriander, fennel and sesame oil had an adverse effect. This was shown by the positive effects given by the former three spices and the negative effects given by the latter three spices.

In this screening experiment, the high levels of white pepper, garlic and onion were 0 . 75%, 0.75% and 0.6% respectively and the ideal ratio scores for desirable flavours and a roma were around 0.8. Therefore , in order to improve flavour and aroma of meatballs, the high levels of these spices had to be increased in further development. The high level of white pepper, however, was set at the same level (0.75%) because there were comme nts by some pane lists that the meatballs were too hot. In addition, commercial meat b alls in Thailand are normally made with a lower content of white pepper, normally at 0. 1 %. The high levels of garlic and onion were both raised to 0.8% which were close to the levels used in this experiment. The high level of garlic would be increased by an additional 0.05% and that of onion by an additional 0.2%. This was due to the reason that the flavour and a roma

of garlic is harsh and persistent but that of onion is mild and sweet. Therefore, the level of garlic was not substantially raised. It should be borne in mind, as suggested by Farrell (1 985) , that garlic (and possibly onion) should be used with extreme caution because of its intense aroma and disagreeable taste when used excessively. Although the Thai people use garlic and onion in cooking, they use these two spices only to add aroma and flavour into foods but do not use them excessively. I n addition , p rocessed meat products in Thailand are not made with too high levels of these spices , for example, fermented Thai style pork sausages (Nam) are made with 0.3% garlic. Therefore, the mutton-based meatballs should be made with not too high percentages of white pepper, garlic and onion if they are to be consumed by the Thais. The minimum levels of white pepper, garlic and onion were increased to 0.5%, 0.6% and 0.6% respectively.