CONTENTS OF SOLUBLE,CELL-WALL-BOUND AND EXUDED PHLOROTANNINS IN THE BROWN ALGA <Emphasis Type="Italic">Fucus vesiculosus</Emphasis>, WITH IMPLICATIONS ON THEIR ECOLOGICAL FUNCTIONS

Phlorotannins are ubiquitous secondary metabolites in brown algae that are phenotypically plastic and suggested to have multiple ecological roles. Traditionally, phlorotannins have been quantified as total soluble phlorotannins. Here, we modify a quantification procedure to measure, for the first time, the amount of cell-wall-bound phlorotannins. We also optimize the quantification of soluble phlorotannins. We use these methods to study the responses of soluble and cell-wall-bound phlorotannin to nutrient enrichment in growing and nongrowing parts of the brown alga Fucus vesiculosus. We also examine the effects of nutrient shortage and herbivory on the rate of phlorotannin exudation. Concentrations of cell-wall-bound phlorotannins were much lower than concentrations of soluble phlorotannins; we also found that nutrient treatment over a period of 41 days affected only soluble phlorotannins. Concentrations of each phlorotannin type correlated positively between growing and nongrowing parts of individual seaweeds. However, within nongrowing thalli, soluble and cell-wall-bound phlorotannins were negatively correlated, whereas within growing thalli there was no correlation. Phlorotannins were exuded from the thallus in all treatments. Herbivory increased exudation, while a lack of nutrients had no effect on exudation. Because the amount of cell-wall-bound phlorotannins is much smaller than the amount of soluble phlorotannins, the major function of phlorotannins appears to be a secondary one.     

Changes in Fish Proteins Caused by Storage in Saline Solution and Their Inhibition by Phosphates.

SUMMARY— It is known that even small concentrations of sodium chloride cause a loss in the solubility of actomyosin in fillets of Baltic herring. This change is prevented by the simultaneous presence of a sufficient amount of phosphates. To date, the mode of action of phosphates is unsettled. This problem has here been studied by the aid of radioactive pyrophosphate.
The fillets were kept in solutions containing sodium chloride, pyrophosphate, or both, at +4°C. The migration of tracer pyrophosphate was followed by application of the auto-radiographic method; at the same time, changes in the solubility of actomyosin were checked. To avoid losses of soluble compounds, the sections for autoradiogaphy were prepared by freeze-drying and paraffin impregnation techniques. It was found that the migration was very rapid: in 24 hr the fillets were completely marked. The rate of migration was also estimated by counting of the sections.
Studies were also made of the changes in the phosphorus fractions of the fillets during the course of standing using 1% pyrophosphate and maximal standing time of 5 days. Initially, there occurred a rapid loss of phosphorus compounds from the fillets; this related to the lipid and nucleic acid phosphorus. The tracer migrated rapidly into the fillets during the first day, and more slowly after this. The bulk of the tracer was in the acid-soluble fraction. Apparently, there also occurred some incorporation into the lipids and nucleic acids.     

Formation of Biogenic Amines during Ripening of Dry Sausages as Affected by Starter Culture and Thawing Time of Raw Materials

Raw materials affect formation of biogenic amines in dry sausages. Effects of thawing time of raw materials and amine-negative starter culture on amine formation were studied on a pilot scale. The levels of biogenic amines, precursor amino acids, pH, water activity, and microbial counts were measured. Use of starter culture significantly decreased levels of histamine, tyramine and cadaverine formed. The effect of thawing time on formation of biogenic amines was dependent on the use of starter culture.     

Biogenic Amines in Dry Sausages as Affected by Starter Culture and Contaminant Amine-Positive Lactobacillus

The effect of an amine-negative starter culture, containing Pediococcus pentosaceus and Staphylococcus carnosus, on the growth and amine formation of an amine-positive contaminant lactic acid bacterium (G 106) was studied in dry sausages. Levels of biogenic amines, precursor amino acids, pH, water activity and microbial counts were measured. Levels of phenylethylamine and tyramine increased in the sausages inoculated with the amine-positive strain. The starter culture did not prevent growth of G 106 or its amine formation capability. However, levels of histamine remained low although G 106 could produce histamine in vitro.