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A comparison of instrumental techniques used to discriminate the cooking quality of spaghetti

M.J. Sissons1,2, L. Schlichting3, N. Egan1, N. Ames4, C. Rhymer4, B. Marchylo3 and I.L. Batey2,5,6

1NSW Agriculture, Tamworth Agricultural Institute, Tamworth, NSW 2340, Australia
2
Value Added Wheat CRC, North Ryde NSW 1670, Australia
3
Grain Research Laboratory, Canadian Grain Commission,Winnipeg, Manitoba R3C 3G8 Canada
4
Agriculture and Agri-Food Canada, Cereal Research Centre, Winnipeg, Manitoba R3T2M9 Canada
5
CSIRO Plant Industry, North Ryde, NSW 2113, Australia
6
Present address: Food Science Australia, North Ryde, NSW 1670, Australia

Introduction

Various instruments have been developed to evaluate the quality of pasta. These instruments include the Instron Universal Testing Machine, the Viscoelastograph and the Matsuo and Irvine (1969) described apparatus for measuring the tenderness of cooked spaghetti (the Grain Research Laboratory Tenderness Tester). More recently, pasta texture has been assessed using instruments such as the TA.XT2i Texture Analyser (Stable Micro Systems, Godalming, U.K). There is however, no comparative information about how the different instrumental methods to measure the firmness of cooked pasta relate and different laboratories have developed there own in house methods for evaluating pasta firmness using TA.XT2i Texture Analyser.

The objectives of this study were (1) to compare the spaghetti firmness results of three laboratories using the TA.XT2i Texture Analyser using their own in house methods and (2) to compare three different instrumental methods to measure the firmness of a wide variety of spaghetti samples. The instruments compared are the TA.XT2i Texture Analyser, the Viscoelastograph and the GRL Tenderness Tester.

Materials and methods

Sample set

A set of thirty commercial spaghetti samples with an uncooked diameter within the range 1.52-1.97mm were selected.

Samples were analysed by the Tamworth Agriculture Institute, NSW Agriculture, Tamworth, Australia (TAI), the Canadian Grain Commission, Grain Research Laboratory, Winnipeg, Canada (GRL) and Agriculture and Agri-Food Canada, Cereal Research Centre, Winnipeg, Canada (CRC).

Methods used to assess pasta quality

Firmness

All laboratories used the TA.XT2i Texture Analyser to assess firmness. Each laboratory used an in-house procedure for testing pasta firmness and different TA.XT2i instrument settings (Table 1).

Table 1. Instrumental settings used for TA.XT2i firmness test according to laboratory.

Lab

Cook method

Load cell mass
(kg)

No strands/
Length (cm)

Rig Type

Test speed
(mm/sec)

Blade distance
stopping short
of base plate
(mm)

TAI

A

5

5 x 7

A/LKB-F

1.0

Stop 0.3

CRC

B

25

4 x 6

TA-47

0.8

Stop 0.5

GRL

C

25

10 x 2.5

Custom

0.2

Stop 0.1

A= Cook pasta (10g) to OCT, drain, cover with 250ml water for 2 min, drain, cover for 1 min then test (3 cooks/sample); B= Cook pasta (15g) to OCT, rinse 130ml water, drain, test three lots of four strands from the one cook; C = Cook pasta (9g) to OCT+15sec, drain, rinse (five times), test five lots of 10 strands from the one cook.

Viscoelastograph

A viscoelastograph (Chopin, Model #Visco V3.50, France) was used at the CRC to measure the relative recovery (%Rr) according to Kovacs et al (1995). Two important measures are the percentage relative recovery (%Rr) and firmness.

Cooking Quality Parameter (CQP)

This test was performed at the GRL laboratory. Spaghetti cooking quality as measured by the CQP was determined as described by Dexter and Matsuo (1977).

Results and discussion

Different absolute values for firmness as measured by peak force were obtained from each laboratory. This is not unexpected given the very different instrument settings and cooking procedures as outlined in Table 1. The GRL values were much higher while the range in values between TAI and CRC were similar. The GRL firmness test cuts 10 strands, uses a low test speed and cuts further into the sample, all of which explain the higher peak force values compared with the CRC and TAI labs. If inter-laboratory comparisons of pasta texture are to be possible, standardisation of the cooking procedure, sample presentation to the texture analyser and instrument settings must be uniform. Further work is required to optimise these steps to permit standardisation of this test between laboratories.

In spite of the differences in instrumental settings and methodologies used between labs, firmness, as measured by peak force was highly correlated (r = 0.85-0.93) among the 3 labs (Table 2). This is reflected in the similarity of the ranks of peak force for the samples and the high rank correlation coefficients between TAI and GRL (r 0.82), TAI and CRC (r 0.86) and between GRL and CRC (r 0.91) (Table 3). For example, TAI ranked the firmest four samples as A1 (1), A8 (2), I7 (3) and A2 (4) compared to GRL which gave ranks for these samples of 2, 5, 6 and 3 and CRC ranks of 3, 4, 2 and 1, respectively. Similarly, the least firm four samples according to TAI were I9 (30), C3 (29), I6 (28) and I10 (27) compared to GRL ranks for these samples of 30, 26, 29 and 25 and for CRC ranks of 30, 28, 29 and 27. Samples between these groups ranked differently with some marked differences but this did not affect the rank correlation coefficient. This highlights the need to perform this test using a standard protocol for instrument settings and cooking procedures if one wants to have consistency between laboratories when ranking samples.

Other measures of pasta texture were obtained using CQP and viscoelastograph. Higher CQP values are associated with pasta that is firm (high peak force) and has the ability to recover from compression (high relative recovery) and a wide range in values was obtained for these samples with many significant differences. This test was highly correlated with firmness (r ~ 0.83-0.94, Table 2). The CQP ranking of the samples showed excellent correspondence with the tests of firmness from each of the three labs. Rank correlation coefficients between CQP and firmness were, r 0.78, r 0.95 and r 0.89 at TAI, GRL and CRC, respectively. The top five ranked CQP samples were within the top 10 group determined by peak force and the bottom five ranked CQP were within the bottom six ranked by peak force. The TA.XT2i test for firmness is quicker to perform than the CQP test and given the similarity of ranking, could replace the latter test.

Viscoelastograph firmness was highly correlated with relative recovery and both these measurements were in turn correlated with peak force and CQP (Table 2). There were good rank correlations between viscoelastograph and peak force although the CQP test more closely matched the ranks by peak force than either viscoelastograph relative recovery or firmness.

Table 2: Correlation coefficients of tests grouped according to similar measurement (firmness).

 

FIRM-TAI

FIRM-GRL

FIRM-CRC

CQP

%Rr

Vfirm

FIRM-TAI

           

FIRM-GRL

0.85

         

FIRM-CRC

0.86

0.93

       

CQP

0.83

0.94

0.90

     

%Rr

0.70

0.75

0.80

0.82

   

Vfirm

0.71

0.78

0.83

0.83

0.98

 

Firmness peak force for the three labs designated as FIRM-TAI, FIRM-GRL, FIRM-CRC; Vfirm = viscoelastograph firmness.

Table 3: Rcank correlation matrix.

 

TAI

GRL

CRC

CQP

%Rr

Visco-Firmness

Firmness-TAI

1.00

         

Firmness-GRL

0.82

1.00

       

Firmness-CRC

0.86

0.91

1.00

     

CQP

0.78

0.95

0.89

1.00

   

%Rr

0.69

0.81

0.78

0.84

1.00

 

Visco-Firmness

0.64

0.79

0.78

0.81

0.97

1.00

Conclusions

This study has found close agreement between three different instrumental methods to measure the texture of cooked spaghetti (CQP, viscoelastograph and TA.XT2i) in terms of high correlations and excellent ranking. However, even using the same instrument to measure firmness (TA.XT2i) there were differences in the ranks for samples that fell between the extremes in firmness. We attribute these differences to variations in the instrument settings, cooking method, and the sample presentation used by the three labs. There is a need to further investigate the impact of specific cooking and testing variables on the firmness of cooked pasta in order to produce a standardized method applicable for wide usage.

References

Dexter, J.E and Matsuo, R.R. (1977) Can J Plant Sci 57:717-727.

Kovacs, M. I. P., Noll, J.S., Dahlke, G. and Leisle, D. (1995). J Cereal Sci 22:115-121.

Matuso, R.R and Irvine, G.N.(1969) Cereal Chem 46:1-6.

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