Diastatic activity in some unifloral honeys L Persano Oddo, E Baldi, M Accorti

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L Persano Oddo, E Baldi, M Accorti. Diastatic activity in some unifloral honeys. Apidologie, Springer Verlag, 1990, 21 (1), pp.17-24. ￿hal-00890807￿

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Diastatic activity in some unifloral honeys

L Persano Oddo E Baldi M Accorti

1 Istituto Sperimentale per la Zoologia Agraria, Sezione di Apicoltura, Via Leonida Rech 36, 00156 Roma; 2 Istituto di Industrie Agrarie, Università degli Studi - Via S Michele degli Scalzi 4, 56100 Pisa, Italy

(Received 31 July 1988; accepted 20 June 1989)

Summary — Determinations of diastatic activity in 12 groups of unifloral honey were made to study variability according to the botanical origin of the honey. Robinia, Citrus, Erica, Taraxacum and Arbu- tus honeys were found to have a very low enzyme content. On the contrary Hedysarum, Castanea, Honeydew, Eucalyptus and Thymus honeys showed high diastase activity. The relationship between the absorbance at 5 min and the diastatic index was quantified.

honey / enzyme activity / amylase / absorbance

INTRODUCTION 1931). Various explanations for the low en- zymatic activity of certain honeys have been proposed, such as a poor processing The presence of enzymes in honey has of nectar by the bees during an abundant been known for many years. One of the nectar flow 1964), or seasonal ac- better known is diastase or (Sipos, enzymes amy- tivity of the pharyngeal glands (Halber- lase. The origin of this enzyme in honey stadt, 1980; Fluri et al, 1982). Even inter- has been attributed to the salivary secre- national standards include honeys with "a tions of bees (Gothe, 1914), or to its pres- low natural content of enzymes" for which ence in pollen (Vansell and Freeborn, different limits are accepted (CAC, 1969). 1929; Lothrop and Paine, 1931), or nectar (Fiehe, 1932; Gorbach, 1942). Today, the Another extensively studied aspect of most widely accepted theory attributes the diastase activity in honey is its susceptibil- origin of diastase in honey to salivary se- ity to temperature and age of the honey. cretions of bees. This conclusion is based Although diastase sensitivity to heat and on the presence of diastase in honey pro- storage is not very high compared to sac- duced by sugar-fed bees, and on the simi- charase (White et al, 1964), the measure- larity between honey diastase and bee dia- ment of diastatic activity is used to evalu- stase (Ammon, 1949; Rinaudo et al, 1973; ate the freshness of honey. The qualitative Stadelmeier and Bergner, 1986). Howev- parameters of the European standards er, this does not explain why honeys of di- (CAC, 1969) prescribe a diastatic index of verse botanical origin show a different dia- no less than 8 on the Gothe scale and no static activity, a fact which has been less than 3 for honeys with a low natural known for many years (Lothrop and Paine, enzyme content.

* Correspondence and reprints. The present study describes variability The selected samples were distributed as fol- of diastase activity in relation to the botani- lows: 92 Castanea unifloral honeys, 76 Robinia, 29 23 22 Arbutus, 18 cal origin of the honey. In addition, to con- Hedysarum, Eucalyptus, Citrus, 15 Helianthus, 11 9 Erica, 9 tribute to the of the Thymus, simplification lengthy Rhododendron, 9 Taraxacum and 30 Honeydew chemical the be- analysis, relationship from spruce fir. The diastatic activity was deter- tween the diastatic index of a honey and mined for the entire assay according to the the absorbance measured at the start of method of Schade et al (1958), modified by the analysis (5 min) was quantified. White and Pairent (1959) and by Hadorn (1961), accepted as the official method of analysis (CAC, 1969). Merck 1252 soluble starch was used after the blue value was verified. The re- MATERIALS AND METHODS sults are expressed in Gothe scale units. The data collected were introduced into a program of During an extensive study of characteristics of simple descriptive processing. Italian honeys (Accorti et al, 1986), 625 honeys of diverse botanical origins, produced in differ- ent years and in various Italian regions were an- RESULTS alyzed for diastase. From these, 343 were cho- sen which, without doubt, could be classified as unifloral The choice was based on or- honeys. The total of the diastatic index ganoleptic characteristics (taste, smell, colour, variability physical state), physico-chemical properties encountered in the assay (625 honeys) (electrical conductivity, specific rotatory power, covered a vast range, from a minimum of total acidity, pH, glucide spectrum) and micro- zero to a maximum of 43.5 (average 18.3 ± scopic characteristics (qualitative and quantita- 9.1). Among the types analyzed, Erica, Ro- tive to melissopalynological analysis) according binia, Taraxacum and Citrus have a low di- the limits described by Accorti et al (1986). astatic index, with an average of 8-10 (fig All the samples had been refrigerated 1 and table I). Particularly low values (av- and were within 12 months (- 20 °C) analyzed 5.2 ± were encountered for the of extraction. Their freshness at the time of erage 3.0) diastatic of Arbutus 2 sam- analysis was verified through the determination activity honeys, of HMF (< 10 mg/kg). ples of which gave a value of zero. These honeys do not, therefore, come within the say (18.3) coincides fairly well with that re- limit of 3 that the law prescribes for honeys ported by White et al (1962) for an assay with a low enzyme content, unlike the pre- of some 500 American honeys (20.8), al- vious types for which the minimum values though their overall range covered much were always greater than 3. higher values (2.1-61.2). It must be pointed out that the samples For the unifloral types the most abun- were fresh and that none of them had dant data are found for Robinia and Citrus been heated, as confirmed by the HMF honeys. For Robinia, all authors give rath- values that were all extremely low. So, the er low values, similar to those found in this obtained values can be considered as research (White et al, 1962; Fini and Saba- characteristic of the examined honeys and tini, 1971; Marletto et al, 1977; Patetta et not dependent on external factors. al, 1977; Ivanov, 1978). Low values have also been reported for Citrus honeys In the other unifloral types, Rhododen- (White et al, 1962; Skender, 1972; Fini and dron and Helianthus showed moderate val- Sabatini, 1974) and are supported by our ues (with an average of 13.7 and 16.3 res- results. Only those obtained by Serra Bon- pectively); Hedysarum, Castanea, Honey- vehi et al (1986) indicate a higher average dew and Eucalyptus where characterized value, of 21.8 ± 4.6. by a high diastatic index, with average val- The scanty data available for the other ues of 20-25. Diastatic activity was excep- unifloral types are often contradictory: for tionally high in Thymus honeys = (average the diastatic in- 33.1 ± 4.7). instance, reported average dex values for Eucalyptus honeys are 18 A comparison of these results with (Serra Bonvehi and Cañas Lloria, 1988), those reported in the literature shows that 21.9 (White et al, 1962), 29.6 (Langridge, while numerous data are available for 1966) and 43 (Fini and Sabatini, 1974), some honeys, they are very sparse or to- whereas for Honeydew honeys, White et al tally lacking for others. The general aver- (1962) give 6.7 to 48.4, and Serra Bonvehi age diastatic index found for the entire as- et al (1986) give an average of 50.2 ± 10.7. The different values obtained by various It is a well-known fact that the 5-min authors may be attributed, at least in part, value gives an approximation of the end to the procedure adopted for the analysis, point (AOAC, 1980; Méthodes Officielles ie the type of starch used (Piazza and Ac- d’Analyse du Miel, 1977), and it was sug- corti, 1981). In certain cases, however, we gested that a definite relationship can be also encountered a considerable differ- established between the diastatic index of ence between minimum and maximum val- a sample and the absorbance read at 5 ues within the same unifloral group, partic- min (Mohamedally, 1979, quoted by Wix, ularly for Castanea and Honeydew honeys 1980). This could be a useful element (table I). since it would enable us to reduce the Values that grossly contradict ours and number of readings and the time neces- that are difficult to explain have been re- sary for analysis. who in ported by Thrasyvoulou (1986), Consequently, since we had 281 paired 125 samples of Greek honey encountered observations of 5-min absorbance and dia- the lowest diastatic values for Thymus stase values we attempted to quantifiy this both for their overall honeys, range (4.5- relationship. The results are expressed in 35.2) and for their average (15.6). An ex- the following linear equation (figure 2) : planation for such a great difference could be that the analysis may have concerned different species of Thymus. Also season- where: = diastatic = absorb- al or bee-dependent factors might have X2 index; X1 ance at 5 min. played a role. The correlation between X1 and X2 is Relationship between initial diastatic index highly significant (r=-0.94949, P < 0.001), and absorbance and also the angular coefficient is signifi- It takes a relatively long time to carry out cantly different from 0 (P < 0.001). Howev- analyses to determine diastatic activity, er, a more detailed analysis of the correla- particularly for honeys with low values. tion within each group of unifloral honeys shows that the lines representing Castan- CONCLUSIONS ea, Eucalyptus, and particularly Citrus hon- Our data show that the diastatic of eys (table II) are considerably detached activity from the general line. Arbutus, Rhododen- the honey is extremely variable among of unifloral This is dron and Taraxacum honeys were repre- groups honey. variability due to a series of uncontrollable sented by an insufficient number of data probably intrinsic and extrinsic factors, and can be for any conclusion. found also to a remarkably lesser degree, This induces us to consider that the within the groups of unifloral honeys. How- phenomenon might be explained more sat- ever, despite this, the honeys with a low isfactorily by a non-linear model. However, enzyme content are clearly distinguished since our objective is basically practical, from those with a moderate or high con- we consider the linear model sufficient for tent. forecasting the time intervals of the read- An important remark must be made con- ings after the first at 5 min. cerning the validity of the limit of 8 units (3 for honeys with a low natural enzyme con- chez lesquels la diastase peut être ab- tent) prescribed for diastase activity by the sente ou en tout cas inférieure au mini- international standards. With the large mum de 3 prévu par les normes. Les miels variation in values found in this study, the d’Hedysarum, de miellat, d’Eucalyptus, de determination of diastatic activity cannot Castanea et encore plus de Thymus ont be considered a valid criterion to measure un indice diastasique élevé. the freshness of Unlike the HMF honey. Cette grande variabilité nous conduit à content which is zero in a theoretically reconsidérer ce paramètre comme indica- fresh it is to know the honey, impossible teur de la fraicheur du miel, car les limites diastase content. original Consequently, légales sont trop larges pour certains types the same value can have a different mean- de miels et trop restrictives pour d’autres. ing according to whether the original con- Finalement, la relation entre l’absorbance tent was high or low. Unless other informa- à la première lecture (à 5 min) et l’indice tion is it is therefore provided, impossible diastasique a été étudiée et quantifiée to give a correct interpretation of the (fig 3, tableau II). Elle est décrite de façon measured values. satisfaisante par l’équation linéaire : We also consider it to be unfair discrimi- nation that the international standards pre- = nombre diastasique ; = absor- scribe a different HMF limit for honeys with (X2 X1 bance à 5 min). a low enzyme content (15 mg/kg instead of 40). We are convinced that a limit of 40 Cela peut contribuer dans la pratique à is too high for any honey, to guarantee its simplifier cette analyse. freshness (Vorwohl, 1969, 1980; Fini and Sabatini, 1972; Piazza and Accorti, 1982; miel / activité enzymatique / amylase / Persano Oddo et al, 1985; Accorti et al, absorbance 1986), but if this value is accepted it should be used for all honeys equally. Zusammenfassung — Diastase-Aktivität in Für 12 Résumé — Activité de einigen Einblüten-Honigen. diastasique quel- italienischer miels monofloraux. L’activité dias- Gruppen Einblüten-Honige ques wurde die Diastase-Aktivität bestimmt a été déterminée 12 tasique pour groupes Robinia, Citrus, de miels monofloraux italiens : Castanea (Castanea, Hedysarum, Arbutus, Erica, Helianthus, Robinia Eucalyptus, (châtaigner), (acacia), Hedysa- Rhododendron, Taraxacum, und Arbutus Thymus rum, Citrus, Eucalyptus, (arbou- Honigtau). sier), Erica (bruyère), Helianthus (tourne- sol), Rhododendron, Taraxacum (pissen- Die große Variabilität dieser Eigenschaft lit), Thymus (thym) et miellat. La grande und die große Abhängigkeit von der botanischen Herkunft dieser wurde variabilité de ce paramètre et le fait qu’il Honige dépend fortement de l’origine botanique du bestätigt und im einzelnen aufgegliedert miel ont été confirmés et quantifiés (fig 1, (Abb 1, Tabelle I). tableau I). En dehors des miels de Robinia Außer für Robinia- und Citrus-Honige, et de Citrus, bien connus pour leur faible deren niedrige Diastase-Werte seit langem indice diastasique, de très faibles valeurs bekannt sind, wurden auch für Taraxacum ont été trouvées pour les miels de Taraxa- (Löwenzahn)-, Erica- und besonders für cum, d’Erica et particulièrement d’Arbutus, Arbutus (Erdbeerbaum)-Honige niedrige Werte gefunden; die Diastase kann bei Fini MA, Sabatini AG (1971) Caratterizzazione diesen fehlen oder als 3 dei mieli italiani. I: mieli di Robinia pseudaca- sogar niedriger 10 115-132 sein, dem im Standard vorgeschriebenen cia. Quad Merceologia (II) Mindestwert. Hedysarum-, Honigtau, Eu- Fini MA, Sabatini AG (1972) Indagine comparati- va sul contenuto in idrossimetilfurfurale dei Castanea- und vor allem calyptus, Thy- mieli destinati al consumo diretto. Sci Tech- haben hohe Diastasewerte. mus-Honige nol Aliment 2 (6), 375-379 Diese große Variabilität zwingt uns, die Fini MA, Sabatini AG (1974) Osservazioni sulla Eignung dieser Eigenschaft als Indikator composizione di alcuni tipi di miele della Sicil- für die Frische des Honigs neu zu ia. Sci Technol Aliment 4 (6), 349-355 überdenken; denn die gesetzlichen Fluri P, Lüscher MM, Wille H, Gerig L (1982) Grenzen sind für einige Honigtypen zu Changes in weight of the pharyngeal gland weit, für andere wieder zu eng. and haemolymph titres of juvenile hormone, protein and vitellogenin in worker honey Schließlich wurde die Beziehung bees. J Insect Physiol 28 (1), 61-68 der ersten 5 zwischen Ablesung (bei Gorbach G (1942) Zur Kenntnis der Minuten) und dem Diastase-Index Stärkeverdaung durch die Biene. II. Mittei- untersucht und quantifiziert (Abb 3 und lung in der Reihe: Ernährungsphysiologische Tabelle II). Sie kann zufriedenstellend Studien an der Biene. 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