La vision d’un industriel sur les coûts de production (vision privée)

Pour tout investissement électrique, il faut considérer d’abord le revenu futur d’une installation et les paramètres liés (marchés interconnectés, enchères de capacités d’interconnexion, coût marginal, oscillation des prix entre les coûts de court terme et de long terme (pour un nouvel entrant)). Il faut aussi considérer la structure de coûts (CO2, combustible, opération, investissement), et la problématique de la gestion des risques auxquels doit faire face l’investisseur (risques de cash flow (retard, responsabilité civile, démantèlement,…) selon ses critères (retour sur investissement). On prend alors en considération les avantages et inconvénients du coût complet du nucléaire, pour qui la sécurité doit être un impératif absolu, ainsi que la problématique du combustible (qui s’analyse comme un investissement), et l’intérêt des partenariats industriels. En conclusion, l’investissement nucléaire est adapté à la conclusion de partenariats de long terme avec des industriels électro–intensifs, dans des structures à définir

Varietal discrimination of hop pellets. II. Comparison between fresh and aged samples

The aim of this study was to assess the stability during storage of several compounds previously described for distinguishing hop varieties. Volatile compounds of five aromatic cultivars (Styrie, Saaz, Lublin, Mount Hood, and Hallertau) and six bitter cultivars (Northern Brewer, Nugget, Pride of Ringwood, Northdown, Target, and Challenger), stored at different temperatures, were extracted with a Likens-Nickerson simultaneous solvent extractor. Only compounds remaining stable through aging were kept to build an identification flowchart. Although very typical of fresh aromatic hops, farnesene proved much too unstable to be selected for distinguishing aged samples. 3-Methylbutylisobutyrate, which authenticates all fresh European bitter hops, is also partially destroyed upon storage. On the other hand, bergamotene, alpha- and beta -selinene, methyl geranate, humulene epoxide II, alpha -amorphene, 2-undecanone, and an unknown compound can be used to distinguish all cultivars whatever the storage temperature. Both the ratios of humulene to humulene + humulene epoxides (I, II, and III) and of bergamotene to farnesene proved good indicators of the freshness status of hop samples

Volatile sulfur compounds in hops and residual concentrations in beer - A review

This review covers most of the published literature on sulfur compounds in hops, especially thioesters, thiophenes, polysulfides, terpens, and thiols

Measuring antioxidant efficiency of wort, malt, and hops against the 2,2'-azobis(2-amidinopropane) dihydrochloride-induced oxidation of an aqueous dispersion of linoleic acid.

This paper presents a simple, convenient method for determining the efficiency of antioxidants in aqueous systems. Production of conjugated diene hydroperoxide by oxidation of linoleic acid in an aqueous dispersion is monitored at 234 nm. 2, 2'-Azobis(2-amidinopropane) dihydrochloride is used as a free radical initiator. Among 12 antioxidants tested, phenolic compounds proved to be the most efficient, both kinetically and in terms of the inhibition time (T(inh)). Applied to wort, malt, and hops, the method confirmed a significant antioxidant activity in such products, especially hops. This assay can be used to follow oxidative changes throughout the brewing process and to understand the contribution of each raw material

Reducing power of hop cultivars and beer ageing

Since lipid auto-oxidation during wort boiling is a determining for the appearance of staling flavour in aged beers, we have investigated the reducing power of hops added in the boiling kettle. An assay based on the inhibition of linoleic acid oxidation in the presence of an initiator [2,2'-azobis(2-amidino-propane) dihydrochloride = AAPH] enabled us to distinguish hop varieties and conditionings. Large differences in hop flavanoid contents explained the higher antioxidant activity of low-cr-acid samples versus bitter varieties and CO2 hop extracts. As expected, adding hop pellets to the kettle effectively increased the overall reducing activity of wort. Supercritical CO2 hop extracts had no significant effect due to their extremely low level of polyphenols. The concentration of the very well-known marker of beer ageing, trans-2-nonenal, was lower in boiled wort exhibiting a better reducing power. The AAPH reducing power test applied to hops or worts was thus efficient to predict the nonenal synthesis during boiling. Hop varieties and conditionings emerged from this work as key-parameters for improving the reducing power of wort and the flavour stability of the final product. (C) 2001 Elsevier Science Ltd. All rights reserved