Indicator on Hagberg Falling Number determination
Introduction
The Hagberg Falling Number (HFN) is an internationally recognized measure, which allows the indirect determination of alpha-amylase activity (alpha-amylase are enzyme that decompose starch). This activity may become excessive if germinated grains are present.
Low values for HFN mean excessive levels of alpha-amylase (Perten, 1964) causing loaves to be discolored, sticky and of poor resilience and texture (Chamberlain et al., 1982). Thus, wheat grains whose alpha-amylase activity is too high do not suit backing industries and rather should be used for animal feeding.
More precisely, below 120 seconds, the wheat grain lot is unfit for bakery use. A value lower than 180 seconds signifies an alpha-amylase activity that may be detrimental to the bread making process. The ideal level of activity is between 180 s and 250 s. However above 250 seconds, the lack of activity may be corrected by adding malt to the batch so that it may be used for bakery (Gatel and Martin, 1999).
Due to the bread baking problems associated with low HFN values, wheat buyers often ask for a guarantee of the HFN in theirs contracts with suppliers.
Laboratory measurements of HFN are conducted according to a standardized method (AFNOR NF V 03-703 standard, September 1997). It aims to measure of the viscosity of a mixture of crushed wheat and water placed in a bain-marie at 100°C.
By the way, repeatability and reproducibility limits of HFN measurement are rather high (ITCF, 2001).
Elaboration of an indicator to determine the Hagberg
Falling Number
Objectives
The interest of the elaboration of an indicator to determine the HFN is twofold.
On the one hand, the prediction of this indicator helps to identify the right time to harvest the crop and allows to target more easily the fields that may benefit from an early harvest even if it involves additional costs due to artificial drying. Indeed, a harvest delayed because of moisture and cooling conditions may lead to low HFN values.
On the other hand, HFN determination makes it possible for the stocking company to classify the batches at harvest and thus to avoid mixing germinated grains with good quality miller wheat.
HFN determination will allow the farmer as well as cereal cooperatives to foresee the possible markets for cereals and thus their prices on the cereal market.
Data to be taken into account
Results of works in the United Kingdom have shown that weather factors can explain the significant annual variations in HFN value (Kettlewell and Cashman, 1997, Kettlewell, 1997).
Indeed, annual variation in alpha-amylase activity and Hagberg Falling Number can be associated with grain drying rates and cumulative potential evapotranspiration during grain ripening and maturation (Kettlewell and Cashman, 1997, Kettlewell, 1997).
Thus the effect of temperature during grain ripening and maturation seems to be decisive to explain the value of this parameter.
High temperatures during the period before the maturity can indeed reduce the critical periods during which grains stay wet because of bad environmental conditions. This leads to a reduction of the risk of germination and its associated alpha-amylase production.
Wheat grains that develop in cool environments have been found to lose their dormancy more rapidly than grains that develop in warm environments, which will facilitate their germination. This phenomenon is intensified with rainfall periods that further delay the grain harvest.
During the grain maturation, cool periods often match rainfall periods and reduced sunshine. Consequently, it is difficult to discriminate the effects of these two factors on the Hagberg Falling Number (RéQuaSud, 2003).
That is the reason why we will focus on the cumulative precipitations during the period of wheat maturation.
The meteorological data have been acquired by the weather radar located at Wideumont (Belgium). These data have a continuous space cover on the whole studied area.
A second variable to take into account is
the kind of the varieties. Indeed, varieties tend more or less strongly
to have low HFN values under ideal climatic conditions.
For instance, varieties that have a deep colour, yellow or brown, are less
sensitive to germination whereas varieties with white grains (example: Recital)
are more sensitive.
La connaissance de la variété sera disponible de manière approximative (par groupement de parcelles) pour 2002 alors qu’elle sera connue pour chaque parcelle agricole de la zone étudiée en 2003, ce qui permettra de valider plus précisément l’indicateur proposé.
The identification of cultivars will be roughly available (as groups of fields) for 2002 whereas it will be known for each field of the studied area for 2003, which will allow validating more precisely the proposed indicator.
L’indicateur d’évaluation de l’indice de chute d’Hagberg sera obtenu par analyse spatiale issue du croisement de ces deux couches d’informations.
The indicator to determine HFN value will be obtained by spatial analysis resulting from the overlay of these two layers of information.
Bibliography
Chamberlain N., Collins T.H., McDermott E.E., 1982. The influence of alpha-amylase on loaf properties in the UK, Proceedings to the 7th World Cereal and Bread Congress, pp. 841-845.
Gatel F., Martin G., 1999. Que revêt la notion de qualité ?, Perspectives Agricoles, n°-250, octobre 1999, pp 5-9.
ITCF, 2001. Contrôle de la qualité des céréales et protéagineux, guide pratique, 2ème édition, pp 197-200.
Kettlewell P.S., 1997. Seasonal variation in the response of Hagberg falling and liquefaction numbers to propiconazole fungicide in wheat, Ann. Appl. Biol., 130, pp 569-580.
Kettlewell P.S., Cashman M.M.,1997. Alpha-amylase activity of wheat grain form crops differing in grain drying rate, J. Agric. Sci.(Cambridge), 128, pp 127-134.
Perten H., 1964. Application of the falling number method for evaluating alpha-amylase activity. Cereal Chem. 41, pp 127-140.
RéQuaSud, 2003. Qualité du
froment d’hiver en région wallonne, note technique, Centre
de Recherches Agronomiques, Gembloux, Belgique, 42 p.
