Diastase, in honey

Fig. 19.12. Inactivation rate of (a) invertase and (b) diastase in honey (according to White, 1978)...

A method for the rapid determination of the a-amylase diastase in honey has been reported. ... 

The protein content of honey is usually around 0.2% (Anklam, 1998 Iurlina and Fritz, 2005). A small portion of this fraction consists of enzymes, notably invertase, diastase, amylase, glucose oxidase, catalase (Anklam, 1998), a-glucosidase, and p-glucosidase (Won et al., 2008). Some are derived from bees, whereas others come from the nectar. Enzyme activity varies among honey samples since the amount of bee saliva, the source of bee enzymes, found in honey varies with the conditions of honey production (Anklam, 1998). 

The most prominent enzymes in honey are a-glucosidase(invertase or saccharase), a- and P-amylases (diastase), glucose oxidase, catalase and acid phosphatase. Average enzyme activities are presented in Table 19.14. Invertase and diastase activities, together with the hydroxymethyl furfural content, are of significance for assessing whether or not the honey was heated. 

The diastase activity was traditionally determined according to the Schade method in the earlier years (Schade et al., 1958). One unit of diastase activity (or more specifically, a-amylase), DN, is defined as that amoimt of enz)nne that converts 0.01 g of starch to the prescribed endpoint in 1 h at 37 °C under the experimental conditions. In this assay, a standard solution of starch, which reacts with iodine to produce a color solution, is used as a substrate for honey enzymes under the standard conditions (Rendleman, 2003). A recently developed procedure uses an insoluble, dyed starch substrate (Persano Oddo and Pulcini, 1999). As this substrate is hydrolyzed by ot-amylase, soluble dyed starch fragments are released into solution. After reaction termination and insoluble substrate removal by centrifugation, absorbance of the supernatant solution (at 620 nm) is measured. The absorbance is proportional to the diastase activity. This procedure has been widely adopted in the honey industry due to the convenience of a commercially available substrate and the simple assay format. 

Serra Bonvehi, J. (1988). Determination of methyl anthranilate in citrus honey (Citrus sp.) of eastern Spain and its influence on the diastase activity of the honey. Alimentaria 197,... 

Effects of Thermal Treatment and Storage on Hydroxymethylfurfural (HMF) Content and Diastase Activity of Honeys Collected from Middle Anatolia in Turkey... 

Thermal treatment, applied to honey, may destroy vitamins and bionutrients, and produce a simultaneous decrease in diastase activity and an increase in HMF content. Honey treatment temperature and time must be limited when pasteurising and stabilising it both diastase activity and HMF content are national and international parameters used as controls so as to limit thermal treatment application. HMF can be formed by hexose dehydration in acid media or by the Maillaid reaction [11,12]. According to Ibarz et al., HMF formation can be described by a second order kinetics (auto-catalytic), with the following equation as expression model [13] ... 

Table 23.2 Diastase number and HMF content of fresh and stored honey samples collected in Middle Anatolia and surrounding areas...

In most European countries, honey is defined in similar terms. However, certain quality factors considered by Europeans, especially the Germans, of importance in the marketing of honey are the levels of the enzymes invertase and diastase, and of 5-(hydroxymethyl)-2-furaldehyde. White has discussed these requirements in relation to suggested standards for the Codex Alimentarius.32 The German insistence on these requirements is outlined in a volume of Apiacta.33... 

To illustrate the use of LDA for food authentication, an example involving the classification of honey samples according to their floral origin will be used [15]. In particular, the data set comprises the results of 15 determinations— pH free, lactone, and total acidity diastase water content specific conductivity dextrose, fiructose and DP2 colour specific rotation hydroxymethyl-furfural (HMF) content and (on the whole sample and on the... 

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