QDPI Farming Systems Institute, Barley Quality Laboratory, PO Box 2282 Toowoomba Queensland 4350 Australia

Abstract

Fifteen genotypes from the Northern Barley Improvement Program Stage IV trial were assessed for malting quality from seven sites in 2000. A range of malt quality, including friability, was obtained from grain samples of variable quality. While friability was included as a new parameter to assist in assessing malt quality for this level of testing, the relationship between friability and other indicators of endosperm modification was not known. It was expected that the friability results would provide additional information on the malting performance of advanced breeding lines. The results indicate that friability, like a number of malt parameters, was significantly (p <0.05) affected by growing site as well as the genotype. Friability was highly correlated to grain protein (-0.52, n=72, p<0.05), plump grain (0.31), IoB extract (0.79), Kolbach Index (0.46) and total protein (-0.57). However, for individual genotypes there was considerable variation in the relationship between these parameters and friability, with most having a significant positive correlation to IoB extract and all samples having a negative correlation to total protein. In addition, for most samples there was a positive correlation between KI and friability while there was no apparent relationship (0.07) between EBC extract and friability for all genotypes assessed under the malting conditions used in this study. Importantly, our results indicate that friability will provide useful information on the malting performance of breeding lines and would assist in rapidly identify malt samples that may be undermodified prior to extensive malt quality analysis.

Introduction

Friability is a measure of the breakdown of malt endosperm cell wall components. Measuring the friability of commercial malt has increasingly been used as an indicator to malting and brewing quality as well as trouble shooting on samples of poor malt quality. The relationship between malt quality parameters and friability have been well documented since Chapon et al. (1978) first reported the use of the Friabilimeter.

Biochemical measures of endosperm modification include malt and wort β-glucan, Kolbach Index and wort viscosity. All of these parameters have been correlated to friability (Chapon et al. 1980; Lie et al. 1981; Bathgate, 1983; Thomas, 1986; Forrest, 1990; Woodward and Oliver, 1990). The relationship between wort β -glucan, Kolbach Index, wort viscosity and other malt quality parameters have been studied through detailed experiment examining malt quality during barley malting (germination) (Chapon et al. 1980; Lie et al. 1981; Bathgate, 1983; Thomas, 1986; Letters et al. 1988; Forrest, 1990; Woodward and Oliver, 1990; Brennan et al. 1996). Most of these studies reported the strong negative relationship between friability and wort viscosity. However, further studies on the residual malt in the friabilimeter indicated where malts were poorly modified then the malt had a high percentage of non-friable material (Chapon et al. 1980; Lie et al. 1981; Bathgate, 1983; Thomas, 1986; Letters et al. 1988;Forrest, 1990; Woodward and Oliver, 1990; Brennan et al. 1996). The non-friable material produced higher wort viscosity than the friable malt fraction.

To date, work studying the useful application of the friabilimeter has been limited to the malthouse or brewery, with limited work conducted evaluating the effect of site or genotype on friability. In this study we have examined the relationship between friability and a number of grain and malt quality characteristics measured in advanced barley breeding material. In addition, we have analysed genotype and environmental effects on friability.

Materials and Methods

Samples

Seven barley cultivars were obtained from seven sites from the Stage IV advanced breeding trials conducted through the Northern Barley Improvement Program.

Grain analysis

Grain size was carried out using a Sortimat. The percentage of the grain size distribution was calculated based on the weight of four fractions, namely < 2.2 mm (screenings), 2.2 – 2.5 mm, 2.5 – 2.8 mm and > 2.8 mm (> 2.8 mm). Plump grain was the combined total of > 2.5 and > 2.8 fractions. For micromalting, grain above 2.2 mm was retained. Barley samples were ground through a hammer mill with a 0.8 mm screen. Grain moisture was determined by EBC method 3.1 (EBC 1997). Grain nitrogen was determined on duplicate samples following the Dumas Combustion Principle in a Leco 428 analyser, calibrated with an EDTA standard.

Micromalting

Micromalting was carried out in a Phoenix automated micromalting unit. The steep stage consisted of 6hr wet, 10hr rest and 6 hr wet at 17^oC (ex-steep moisture 40%). Germination was four days in length at 17^oC. Kiln stage was set to have the moisture of the dried malt at approximately 4.5^oC.

Malt analysis

Friability and malt moisture was determined using the respective EBC methods. Malt extract was carried using two methods. The first method was a single temperature infusion mash at 65^oC based on the Institute of Brewing style (Fox and Henry, 1990). The second comprised a 1:5 scale of the EBC method (EBC, 1997). Kolbach Index (KI) was determined from total and soluble nitrogen levels measured using the Dumas Combustion Principle. For total nitrogen (TN) the system was calibrated with EDTA. For soluble nitrogen (SN), 0.1% glycine (w/v) was the calibrant.

Diastatic power (DP) was measured using a procedure Fox et al. (1999) where enzymes were extracted with NaCl. American Society of brewing Chemists (ASBC) starch was used as the substrate. The amount of reducing sugars was determined using p-hydroxybenzoic acid (PAHBAH). Malt α-amylase was determined from the same extract prepared for the DP assay, with amylase activity measured by the Phedabas procedure.

Statistical analysis

All data was analysed for environmental and genotypes effects by Analysis of Variance (Genstat 5^th edition). In addition, correlations between the various characteristics measured was carried out using Genstat (5^th edition).

Results and Discussion

The relationships between friability and malt parameters were variable between sites and genotypes. While there were varying relationships between friability and other malt quality parameters, the correlation between friability and IoB extract between genotypes was significant (p < 0.001) (Tables I, II and III). For each genotype there was a positive relationship between friability and IoB extract. This supports previous results from commercial brewery runs (J. Armitt pers comm.). The results from our study would suggest that the level of physical breakdown of cell walls and protein components during malting (friability) had a direct impact upon the IoB extract performance of each genotype. Friability and IoB extract data from a number of samples of a single genotype, assist in building a performance profile for that genotype. Cross comparisons of genotypes could then be conducted based on this performance profile..

For both sites and genotypes, strong negative correlations existed for friability and TN. The negative relationship between friability and TN increased when samples were grouped into levels of modification, ie. < 40, > 40 and > 42. Suggesting IoB extract more genetically controlled. Within genotypes the higher extract varieties, Tallon and Lindwall, also averaged the highest friability, regardless of their KI suggesting genetic effect more than a processing effect. While IoB extract remained positive for all sites and genotypes the EBC extract was variable suggesting that the IoB method would be a much better indicator of malting performance and a mashing predictor than EBC.

In this study malt quality data for seven genotypes was evaluated from seven sites. The malt quality data is shown in Table IV. Analysis of the data within and between sites showed significant effects (p < 0.05) for sites and genotypes for all traits measured. There was no significant genotype x site effect for those same traits. Sites had the largest effect on protein, grain size, IoB extract and DP, while genotype had the largest effect on EBC and KI. These results were similar to previously reported results for genotype and environmental effects on grain and malt quality (Arends et al., 1995). Both sites and genotypes had a significant effect on friability which agrees with the results previously reported (Molina Cano et al. 2000, Woodward and Oliver, 1990).

Limited starch hydrolysis takes place during the malting process. Key starch degrading enzymes were measured via the diastatic power method or directly through the α-amylase assay. The results indicate that for individual genotypes there was no significant correlation with friability. While Brookstead was the only site that showed a significant correlation between Friability and DP and AA. Friability had previously been correlated to key enzymes responsible for breakdown endosperm cell wall components (Altunkaya et al.2001) and hordein degradation (BQL unpublished).

The relationship between plump grain and the > 2.8 mm fractions and friability was positive for six of the seven genotypes. Consideration should be given to the assessment of genotypes with large kernels. While large kernels could potentially provide high levels of extract, this may not always be the case. If large kernels were undermodified then potential processing problems which may not be detected via EBC analysis. While there was a positive correlation for most genotypes, the strongest correlations were not necessarily the genotypes with higher levels of modified.

Conclusions

Friability has been demonstrated to be a useful tool in understanding the variable performance of malt quality which may not necessarily be explained through routine malt analysis. At this stage, the application of the friabilimeter has been limited to malting and brewery sample analysis and in particular brewhouse performance (Palmer 1996; van Lonkhuijsen et al. 1998; Axcell, 1998). However, an additional application would be in the assessment of barley breeding material. Routine assessment of advanced breeding lines includes determining hot water extract, endosperm modification and the hydrolytic enzyme levels. Many sites are used to gain an understanding of overall quality performance of a potential malting variety.

Acknowledgements

The authors gratefully acknowledge the continuing support of GRDC for the Northern Barley Improvement Program.

References

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Table I. Interactions between genotypes and sites for grain and malt quality parameters.

Parameter	Genotype	Site
Scr	ns	*
> 2.8	***	***
PG	*	***
GP	*	***
FRI	***	***
IoB	**	***
EBC	ns	***
KI	*	***
TN	ns	***
SN	***	*
DP	***	***
AA	***	***

ns not significant, * p < 0.05, ** p < 0.01, ***p < 0.001

Table II. Correlation coefficients for Friability and grain and malt quality parameters between sites

Parameter	All sites	Brookstead	Delungra	Hermitage Irrigated	Jondaryan	Purlewaugh	Roma	Warialda
Scr	-0.37*	0.49	0.16	0.83	-0.41	-0.60	-0.44	0.32
> 2.8	0.58**	-0.50	-0.16	-0.84	0.25	0.05	-0.11	0.35
PG	0.51**	-0.57	-0.45	-0.85	0.29	0.71	0.37	0.05
GP	-0.61**	-0.31	0.24	0.88	0.27	-0.88**	0.25	-0.29
IoB	0.60**	0.80	0.56	0.93	0.06	0.09	0.53	0.23
EBC	0.13	0.63	-0.09	-0.85	0.22	-0.39	-0.52	-0.01
KI	0.57**	0.96**	-0.43	0.69	0.33	-0.27	0.53	0.57
TN	-0.71**	0.69	-0.09	0.45	0.82*	-0.76*	0.07	-0.49
SN	0.01	0.99***	-0.28	0.62	0.53	-0.74	0.55	0.55
DP	-0.14	0.98**	-0.23	0.63	0.38	-0.02	0.43	0.30
MAA	0.34*	0.96**	0.32	0.93	0.03	-0.35	0.72	0.40

* p < 0.05, ** p < 0.01, *** p < 0.001.

Table III. Correlation coefficients for Friability and grain and malt quality parameters between genotypes

Parameter	Grimmett	Lindwall	Tallon	Schooner	B%1302	CK123	CK85
Scr	-0.60	-0.52	-0.43	-0.05	-0.45	-0.80**	0.44
> 2.8	0.85	0.83	0.71*	0.57	0.55	0.71*	-0.08
PG	0.87	0.68	0.60	0.32	0.59	0.77*	-0.40
GP	-0.90	-0.79*	-0.56	-0.63	-0.90**	-0.70*	-0.48
IoB	0.73	0.64	0.37	0.50	0.61	0.83**	0.67
EBC	0.73	0.53	0.24	0.02	-0.32	0.11	0.02
KI	0.55	0.78	0.35	0.52	0.92***	0.89**	0.78*
TN	-0.70	-0.94*	-0.78*	-0.80	-0.84**	-0.86**	-0.66
SN	0.32	-0.22	-0.51	0.11	-0.16	0.42	-0.03
DP	-0.63	-0.46	-0.43	0.54	0.03	0.26	0.20
MAA	-0.62	-0.06	0.08	0.00	0.39	0.63	0.61

p < 0.05, ** p < 0.01, *** p < 0.001

Table IV. Summary of quality data from Stage IV (Advanced) breeding trials

Cultivar

Screening % < 2.2 mm

% > 2.8 mm

Plump Grain % 2.5mm

Grain Protein % db

Friability %

IoB Extract % db

EBC Extract % db

Kolbach Index

Total Nitrogen % db

Soluble Nitrogen mg/l

Diastatic Power U/g

Alpha Amylase U/g

B%1302

2.2b

44.1bc

85.8b

10.9a

77.8ab

69.5ab

78.2a

32.3bc

1.80a

615c

484ab

132bc

Cameo/Koru 85

1.6c

55.1ab

91.1ab

10.5a

68.7b

66.7b

80.2a

29.8c

1.72a

537c

408bc

112c

Cameo/Koru 123

3.0ab

34.5c

79.5bc

10.8a

68.3b

66.7b

78.5a

31.9bc

1.69a

568c

388c

118c

Grimmett

1.9c

47.5bc

87.5a

10.7a

77.5ab

68.9ab

78.4a

37.8ab

1.79a

701b

515a

145b

Lindwall

3.1a

36.2c

80.1bc

10.7a

83.9a

71.0a

80.4a

40.4a

1.75a

749ab

509a

155ab

Schooner

1.2c

66.6a

94.3a

11.2a

79.2ab

70.2a

79.4a

41.2a

1.91a

840a

522a

148b

Tallon

2.3ab

47.1bc

84.7b

10.9a

76.5ab

69.0ab

79.0a

36.0ab

1.77a

711b

476ab

176a

LSD p <0.05

0.9

14.8

7.2

1.5

12.7

3.1

2.8

5.6

0.26

93

84

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