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

Effect of a condenser on the analysis by dynamic headspace-GC-MS of the volatile fraction of a cheese

The insertion of a condenser in the dynamic headspace - GC-MS analysis circuit allows part of the water contained in a water-rich sample to be condensed. The impact of such a condenser on the chromatographic profiles of a cheese was studied for temperatures ranging from $-12$ to $0~^\circ$C. The condenser collected the water, but also some of the volatile components of the cheese, irrespective of its operating temperature. Insertion of a condenser improved the overall quality of the chromatographic signal, but caused major changes in the chromatographic profile of the cheese

Analytical artifacts caused by the presence of water vapor in the headspace of food products

Artifacts due to water that appear during analysis by purge-and-trap/GC/MS of naturally moist products were reproduced by increasing the relative humidity of the headspace of measuring cell containing dry and low-moisture products (dehydrated beef stock and powdered Parmesan cheese) by means of a piece of moistened glass wool. The changes observed in the chromatographic profiles of the dry products after humidifying the headspace are explained by interactions between volatile compounds, water and the adsorption trap during the purge-and-trap step

Ultraviolet-absorbing compounds in milk are related to forage polyphenols

International audienceThe aim of this work was to characterize UV-absorbing compounds (UAC) in milk in relation to diet. In winter, 4 groups of cows each received a different diet: concentrate rich containing 35% cocksfoot hay (CCH), maize silage (MS), rye grass silage (RS), or rye grass hay (RH). In summer, 2 additional diets were given: mountain grassland hay (GH) and mountain grassland pasture (GP). Polyphenols were analyzed by HPLC and Folin reaction on forages and UAC were extracted from milks and analyzed by HPLC. In forages, the number of polyphenols was lowest in MS (57) and greatest in GP (85). Twenty-four peaks were identified, accounting for 28 to 47% peak area at 280 nm. Caffeoyl compounds and flavonoid glycosides were mainly found in RH, GH, and GP. Hydrolyzed compounds such as hydroxycinnamic acids and aglycones were found in MS and RS. Estimated amounts of polyphenols were lowest for MS (3.7 g/kg), roughly similar for CH, RS, and RH (about 15 g/kg), and greatest for GH and GP (21.6 and 35.3 g/kg, respectively). About 230 different peaks were separated in milks. Milks from RH and GP contained the lowest (87) and the greatest (127) numbers of peaks, respectively. Only 10 peaks were identified, accounting for 21 to 54% of the total spectra area. In addition to the major compound hippuric acid, phenylacetic acid, benzoic acid, 4-hydroxybenzoic acid benzaldehyde, catechol, and small amounts of ferulic acid were found in varying amounts depending on the diet. Flavonoids such as quercetin, luteolin, and apigenin were also present. Hippuric acid was clearly related to the presence of caffeoylquinic compounds in forages. Other identified UAC may originate essentially from forage simple polyphenols or from cell wall aromatics. Some of the several unknown compounds may also originate from the transformation of other nutrients. Estimated amounts of UAC were widely variable within each animal group. They were surprisingly high in CCH and roughly similar in all milks from preserved forages (about 3.6 mg/L), with generally greater values for GH milks, whereas the greatest amount was found in GP milks (13.3 mg/L). Hierarchical clustering clearly discriminated the 6 diets, showing that there were major differences in GP milks. Some UAC were specific to one or a group of diets. Ultraviolet-absorbing compounds are therefore a potential tool to distinguish between milks according to diet. In addition, they may have a bioactive effect on milk component conservation or on human health

Influence of a native strain of Staphylococcus xylosus on the microbiological, physicochemical and sensorial characteristics on milano salami type

In this work, the influence of native starter cultures on the microbiological, physicochemical and sensorial characteristics of Milano salami type was studied. Two batches of Milano salami type were produced: Batch A, with the addition of Staphylococcus xylosus U5 and Batch B (control) without the starter culture. The Milano salami type was characterized by an important microbial activity of coagulase-negative staphylococci (CNS) that resulted in substantial growth in Batch A during the ripening with an initial count of 7.60 log cfu.g-1 and reached 9.84 log CFU.g-1 after 14 days. Bacterial enzymes that showed efficient activity under the conditions found in Milano salami type were catalase, nitrite and nitrate reductase, contributing for sensory and physicochemical properties of the product. There were no significant differences in general free fatty acids composition among the batches, while the color parameters (L *, a * and b *) in the Batch A presented significantly higher values in relation to Batch B. Moreover, batch A had the higher preference in sensorial analysis.<br>A análise da influência de culturas iniciadoras nativas nas características microbiológicas, físicoquímicas e sensoriais de salame tipo Milano foi o objeto deste estudo. Foram produzidos dois grupos de salame tipo Milano: Grupo A - com aplicação de linhagem Staphylococcus xylosus U5 enquanto o controle, Grupo B, foi produzido sem culturas iniciadoras. O salame tipo Milano foi caracterizado pela importante atividade microbiana de estafilococos coagulase negativo (SCN), que resultou significativo crescimento no Grupo A durante a maturação, com contagem inicial de 7,60 ufc.g-1 e alcançando um crescimento de 9,84 cfu.g-1 depois de 14 dias. As enzimas bacterianas que mostraram eficiente atividade sob as condições encontradas no salame tipo Milano foram catalase, nitrito e nitrato redutase, contribuindo para as propriedades físicoquímicas e sensoriais do produto. Não houve diferenças significativas na composição geral dos ácidos graxos livres entre as amostras, enquanto os parâmetros de cor (L*, a* e b*) obtidos no salame inoculado (Grupo A) diferiram significativamente em relação ao controle (Grupo B) e foi o grupo preferido pelos degustadores