The effects of salicylic acid (SA) and hydrogen peroxide (H2O2) on freezing tolerance were studied in two potato (Solanum tuberosum) cultivars (Alpha and Atlantic) that differ in cold sensitivity, Alpha being more tolerant to freezing than Atlantic. Lowest freezing survival rates were observed in 4‐week‐old plants. Freezing treatments consisting of exposure to 6° C for 4 h in the dark were applied 24 h after plants had been transferred from in vitro culture to soil. Catalase activity and H2O2 were estimated at the following harvest points: stage (a) 4‐week‐old in vitro plants treated with either 0.1 mM SA or 5 mM H2O2; stage (b) as in (a) but 24 h following transfer to soil prior to freezing treatment; stage (c) as in (b) but measured 15 days after a 4‐h freezing treatment. The results show that (1) SA induced freezing tolerance in both cultivars; (2) SA inhibited ascorbate peroxidase activities in both cultivars at all harvest points but inhibited catalase activities in only at stage (a); (3) SA induced H2O2 accumulation only in Atlantic at stage (a); (4) H2O2 enhanced shoot catalase activities in Atlantic at stages (a) and (b) whereas this treatment had no effect on shoot catalase activities in Alpha; (5) H2O2 treatment induced freezing tolerance in Atlantic, even though shoot catalase activities were lower than those of the controls following exposure to freezing temperatures. We conclude that SA does not always lead to H2O2 accumulation even though catalase and ascorbate peroxidase activities are decreased as a result of the treatment. Moreover, H2O2 accumulation is not always associated with the induction of freezing tolerance, for example at stage (a) where SA‐induced tolerance in Alpha was not accompanied by H2O2 accumulation. H2O2 was able to induce freezing tolerance only in Atlantic, even though H2O2 accumulated in both cultivars following this treatment.

The combined effects of pH, temperature (T), substrate/buffer ratio (S:B) and enzyme concentration (E) on protein recovery from gold carp (Carassius auratus) processing waste with Flavourzyme  were characterised. The effect of hydrolysis parameters on the degree of hydrolysis (DH) was described through response surface analysis (RSA) and the model obtained was defined as follows: DH = −316.30+ 7.1T + 44.5pH + 0.292S:B + 0.27E − 0.048T 2 − 2.407pH 2 − 0.002S:B 2 − 0.307TxpH − 0.002S:BxE. All regression coefficients were significant (α = 0.05). The model showed a good fit with the experimental data, since the R 2 of 0.923 indicated that 92.3% of the variability within the range of values studied could be explained by the model. The mathematical model presented a plateau region with a maximum DH (>26.6%) at the following critical values: pH = 5.9, T = 53 • C, S:B = 14.7% and E = 80 LAPU (leucine aminopeptidase units) g −1 . Electrophoretic (SDS-PAGE) patterns showed a progressive reduction in molecular weight of the peptidic fractions from 10 min of hydrolysis onwards. By controlling the enzymatic process, it was possible to predict the molecular weight of the peptides obtained, in turn affecting the functional and nutritional properties of the peptidic fractions.

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This paper presents an extension of a general parametric class of transitional models of order p. In these models, the conditional distribution of the current observation, given the present and past history, is a mixture of conditional distributions, each of them corresponding to the current observation, given each one of the p-lagged observations. Such conditional distributions are constructed using bivariate copula models which allow for a rich range of dependence suitable to model non-Gaussian time series. Fixed and time varying covariates can be included in the models. These models have the advantage of straightforward construction and estimation for the analysis of time series and more general longitudinal data. A poliomyelitis incidence data set is used to illustrate the proposed methods, contrary to other researches' conclusions whose methods are mainly based on linear models, we find significant evidence of a decreasing trend in polio infection after accounting for seasonality.