The use of model systems containing purified anthocyanins, chlorogenic acid (CG), and blueberry polyphenol oxidase (PPO) and of different analysis methods (HPLC and polarographic methods) have allowed the study of the mechanism of anthocyanin degradation by PPO. Cyanidin 3-glucoside (Cy 3-glc) was not oxidized by PPO since no molecular oxygen was consumed. However, the presence of CG induced pigment degradation. The quinone of CG, formed enzymatically, was involved in the degradation of Cy 3-glc by coupled oxidation mechanisms with partial regeneration of CG. This means that part of the CG was incorporated into the degradation products of Cy 3-glc. The ratio of degraded Cy 3-glc to oxidized CG was equal to 2. An anthocyanin degradation mechanism is proposed.

Wood preservatives based on protein borates and in particular albumin borate greatly retarded the leaching of boron from treated timber. Accelerated biological tests indicated that boric acid partially fixed to timber by formation of a salt with albumin and other proteins which are then insolubilised by heat-induced coagulation can yield durability comparable to that obtained with CCA wood preservatives. The results of the biological tests show that protein borates, and particularly albumin borate, can be classified as long-term, wide-spectrum, ground-contact, heavy-duty wood preservatives, and are only composed of boric acid, a non-toxic to mammals biocide and of a non-toxic, natural, sometimes waste material, namely a protein. Investigation of the chemical mechanisms of boric acid fixation by the protein indicated that both acid-base salt formation occurs, as well as the further formation at increasing boric acid proportions of additional boric acid/protein complexes. The mechanism is hence only one of partially reversible rather than totally irreversible fixation of boron, leaving at all times small amounts of boron free to exercise its antifungal activity, but drastically diminishing its tendency to leach and greatly retarding its leaching. Boric acid leaching as a function of exposure time appears to tend to an equilibrium value which is different for each type of protein used and differs in the case of treated timber from that obtained by just leaching of the protein borate coagulum.

Wood preservatives based on protein borates, both obtained by just mixed water solutions of protein and boric acid, as welt as in the case of premanufactured protein borates salts are shown to be a good method to greatly retard the leaching of boron from treated timber. Hence just premixed albumin + boric acid, premanufactured albumin borate and soja protein + boric acid all showed good preservative performance and much retarded leaching of boron. Accelerated biological tests indicated that boric acid partially fixed to timber by formation of a salt with albumin and other proteins which are then insolubilised by heat-induced coagulation can yield durability performances comparable to those obtained with CCA wood preservatives. The results of the biological tests show that protein borates, and particularly albumin borate, can be classified as long-term, wide-spectrum, ground-contact, heavy-duty wood preservatives, and are only composed of boric acid, a non-toxic to mammals biocide and of a non-toxic, natural, sometimes waste material, namely a protein. The mechanism is one of partially reversible rather than totally irreversible fixation of boron, leaving at all times small amounts of boron free to exercise its antifungal activity, but drastically diminishing its tendency to leach and greatly retarding its leaching. Boric acid leaching as a function of exposure time appears to tend to an equilibrium value. The timber is treated by just single stage, water-borne vacuum/pressure treating cycles as for traditional wood preservatives. Nicht-toxische Albumin-und Soja-Proteinborate als 5rf~r Holz mit Bodenkontakt Holzschutzmittel auf der Basis yon Proteinboraten wurden entweder einfach durch Verr/ihren der wgssrigen L6sunyen yon Protein und Bors/iure hergestellt oder als vorgefertigte Protein-Bors/iuresalze verwendet. Die Proteinsalze erwiesen sich als sehr wirkungsvoll gegen.das Auswaschen yon Bor(s/iure) aus behandeltem Holz. Bors/iuresalze mit Albumin und Sojaprotein zeigtem zudem gute Schutzwirkung gegen Pilzbefall. Die Bors/iure ist dabei teilweise fixiert durch Ausbilden yon Salzbindungen an die Proteine, welche ihrerseits durch W/irmebehandlung, d.h. Koagulation unl6slich gemacht werden. Diese salze erreichen im beschleunigten biologischen Test ~ihnliche Schutzwirkungen wie CCA-Holzschutzmittel. Die biologischen TestCorrespondence to: A. Pizzi zeigten, daft die Proteinborate, insbesondere Albuminborat als Holzschutzmittel ffir folgende Anwendungen charakterisiert werden kann: Langzeitwirkung, breites Spektrum, f/.ir Bodenkontakt und hochwirksam. Sie bestehen nur aus der ftir S/iuger ungiftigen Bors/iure und aus nicht toxischen, nattirlichen, zuweilen auch als Abfallprodukte vorkommenden Proteinen. Die Wirkungsweise beruht auf der teilweise reversibelen Fixierung der Bors/lure, wodurch einerseits jederzeit geringe Mengen freier Bors/iure als pilzhemmender Stoff zur Verfiigung steht, andererseits aber das iibliche Auswaschen der Bors/iure drastisch verlangsamt wird. Der Verlauf der Bors/iure-Auswaschung scheint ein...

No abstract

Materials and methods Ten specimens for each case of Pinus sylvestris sapwood of dimensions 50 • 15 x 5 mm were treated under 15 minutes vacuum (-1 bar) and 30 minutes at atmospheric pressure with solutions of (1) boric acid (5% weight/volume) + Pinus radiata tannin extract (1% w/v) + egg albumin (1% w(v), (2) boric acid (5% w/v) + Pinus radiata tannin extract (1% w/v) + collagen (animal glue AT 400, 1% w/v), and (3) boric acid (5% w/v) + Pinus radiata tannin extract (1% w/v). Untreated specimens were also prepared. The specimens were dried at 103 ~ for 4 hours. Half of the untreated and treated specimens were leached for 5 days in 20~ water using lots of 50 ml water for each specimen, changed each day with a fresh 50 ml volume of water. The leaching waters were analysed for leached proteins (Li; Tanner; Larkin) (no proteins leached), leached boric acid (Li; Tanner; Larkin) and leached tannin (Thevenon; Pizzi; Haluk); [all of the tannin was still in the wood after 5 days leaching for cases (1) and (2), while 97.2% of the tannin remained in the wood for case (3)]. Leached and unleached specimens were incubated for I month at 25 ~ on agar medium in Petri dishes inoculated with Coniophera puteana, Gloeophyllurn trabeum and Poria placenta.On each plate a leached or unleached untreated control specimen was also evaluated for % mass loss.Results and discussion The results in Table 1 indicate that the combination of tannin and proteins helps to fix the boric acid or at least to greatly retard its leaching when comparing the results to a boric acid/tannin system. While the top-performing albumin borate does not show any marked improvement when tannin is added in relation to albumin borate alone (Thevenon; Pizzi; Haluk), the collagen borate performance improves markedly when tannin is present in relation to soluble collagen borate alone (Thevenon; Pizzi; Haluk). This is due to the insolubilization of collagen by reaction with tannin by a reaction identical to what occurs in leather tanning. If not coupled with tannin, collagen based animal glue and collagen borates have instead been proved to remain soluble (Thevenon; Pizzi; Haluk)and thus to lead to much worse performances. Both albumin borate and collagen borate were added together with the tannin solution in a single impregnation step into the wood, the stability at ambient temperature of the mixed solutions being due to the low tannin concentration (at much higher tannin concentrations this would not be possible). This allows then a single step water-borne treatment with its consequent economic and technical advanFig. 1. Fungal attack on pine sapwood impregnated with boric acid (5%) + tannin (1%) + collagen (1%) as well as untreated controls (specimens at bottom) Bild 1. Pilzbefall auf Kiefernspllntholz nach Impriignierung mit einem Gemisch aus Bors~iure, Tannin und Collagen sowie unbehandelte Kontrollproben (untere Reihe) L~: 2 .r Fig. 2. Fungal attack on pine sapwood impregnated with boric acid (5%) + tannin (1%) without protein Bild 2. Pilzbefall auf Kiefernsplinth...