La tendance des miels à cristalliser : nouvel essai d'approche statistique

Abstract - Tendency of honeys to crystallize: a renewed attempt at a statistical approach
This study, which continues the 1987 investigation, has attempted to correlate the tendency of market honeys to crystallize with technological production data that can be measured but not always controlled. Twenty-five typical honeys from Western Europe were liquified, heated at 78 °C for pasteurization and placed in 100 glass tubes which were kept at 5, 10, 15 and 20 °C. Each tube was observed at 8 different times for 17 months, and was graded from 0 (none) to 9 (hard crystallized) (800 gradings in all). The statistics cover five tables, with an analysis of variance of the grade together with the storage temperature and duration (table II), and multiple stepwise linear regressions of the grade on the initial composition and viscosity of liquid honey (table III), as it stands just before pasteurization. The development of graining is shown in figures 3 and 4. There is no significant difference between storage temperatures of 10, 15 or 20 °C. Storage at 5 °C begins with a so-called "latent" time without any crystallization, but then graining will develop at the same constant rate as the other temperatures. These results are discussed in terms of crystallization technology; an important but not obvious role of the initial viscosity is presumed. At the beginning of storage, the grade cannot be predicted from the controlled factors. In case of longer storage times, on the contrary, the grade may be predicted from the initial composition and viscosity of the honey. As an example, a regression formula is given for 15 months storage at 15 °C, wherein the calculated grades are in rather good agreement with the observed true grades (fig 5). The grade variability is also rather well explained - about 80% - when considering the majority of honeys, but a few varieties present atypical behaviour: whatever the storage temperature and time, rape honeys always crystallized very fast, whereas Robinia honeys never crystallized. This is why, when considering the entire batch of honeys, only 50% of the variability is explained. Improvement of this score would undoubtedly require a better knowledge of the factors which play a part in graining tendency, especially more thorough compositional analyses of a wide variety of honeys.