Combined effects of potassium sorbate,hot water and thiabendazole against green mould of citrus fruit and residue levels

Postharvest treatments of potassium sorbate only controlled recently established infections of Penicillium digitatum on Femminello siracusano lemons but did not confer any persistent protection. The loss of efficacy of potassium sorbate to control green mould decay was related to its irregular deposition on the fruit surface, as revealed by environmental scanning electron microscopy of oranges, and to the brief persistence of potassium sorbate residues. When treatment was done at 53 °C, the co-application of potassium sorbate with thiabendazole reduced thiabendazole residues in Moro and Sanguinello oranges, compared to thiabendazole treatment alone. However, treatment efficacy against two isolates of P. digitatum (thiabendazole-sensitive and thiabendazole-resistant) notably improved, indicating that potassium sorbate and hot water potentiated thiabendazole activity. Potassium sorbate residues remarkably decreased during fruit storage and were not affected by the co-application of thiabendazole.     

Structuring and texturing gluten-free pasta: egg albumen or whey proteins?

The effects of adding egg albumen or whey proteins to pasta made from parboiled rice flour (PR) were investigated. Pasta quality was evaluated in terms of color, furosine content, and cooking properties (water absorption, cooking loss, and consistency at the optimal cooking time). The surface heterogeneity of the cooked and uncooked materials was studied, and some starch properties (pasting properties and starch susceptibility to α-amylase hydrolysis) were assessed, along with the features of the protein network as determined by conditional solubility studies and with ultrastructural features of the cooked products. Egg albumen improved pasta appearance and gave a product with low cooking loss, firmer, and nutritionally more valuable than the other ones. In albumen-enriched pasta, small starch granules appear homogeneously surrounded by a protein network. In the uncooked product, the protein network is stabilized mostly by hydrophobic interactions, but additional disulfide interprotein bonds form upon cooking. Thus, addition of 15 % liquid albumen to PR results in significant improvement of the textural and structural features of rice-based gluten-free pasta.     

Influence of starter cultures on the generation of antioxidant nitrogen compounds in Iberian dry‐fermented sausages

The purpose of this work was to investigate the influence of a starter culture on the generation of nitrogen compounds with antioxidant activity during the ripening of Iberian dry‐fermented sausages. Starters P200S34 (P. acidilactici M200 and S. vitulus RS34) and P198S34 (P. acidilactici MS198 and S. vitulus RS34) were used to make the Iberian dry‐fermented sausages ‘salchichón’ and chorizo; then, the physicochemical and microbial properties were determined during the ripening process. The oxygen radical absorbance capacity (ORAC) assay was employed to evaluate the antioxidant potential of the nitrogen extracts obtained during ripening of the sausages. This activity was correlated with the most relevant compounds detected by HPLC‐ESI‐MS in the final ripened extracts. Although a relevant part of the antioxidant activity was attributed to the predominant natural nitrogen fraction, the microbial population found in fermented sausages and the fermentation conditions significantly influenced the low molecular weight nitrogen profile and antioxidant activities. Inoculation with the starter culture P200S34 increased free amino acids and amines, such as methionine and tyramine, but other nitrogen compounds also increased the antioxidant activity of the low molecular weight nitrogen extracts. Thus, these starter cultures in Iberian sausages can contribute to delaying oxidative changes during storage.     

Influence of damaged starch on cookie and bread-making quality

In this study two wheat and one triticale cultivars were milled in a disc mill to obtain different levels of damaged starch. The effects of the damaged starch content on physicochemical flour tests and cookie and bread-making quality were analyzed. The grain milling conditions in disc mill and grain hardness influenced the amount of damaged starch. The solvent absorption of flours, as measured by Solvent Retention Capacity Profile (SRC) and Alkaline Water Retention Capacity (AWRC), was significantly incremented by the damaged starch content. There was a consistent loss in cookie quality as the damaged starch content increased. In spite of the fact that the proteins were not affected by flour milling, bread quality decreased as the damaged starch content increased.     

Use of images in shelf life assessment of fruit salad

Fruit salads stored for different lengths of time as well as their images were used to estimate sensory shelf life by survival analysis. Shelf life estimates obtained using fruit salad images were longer than those achieved by analyzing the real product. This was attributed to the fact that images are 2-dimensional representations of real food, probably not comprehensive of all the visual information needed by the panelists to produce an acceptability/unacceptability judgment. Images were also subjected to image analysis and the analysis of the overall visual quality by a trained panel. These indices proved to be highly correlated to consumer rejection of the fruit salad and could be exploited for routine shelf life assessment of analogous products. To this regard, a failure criterion of 25% consumer rejection could be equivalent to a score 3 in a 5-point overall visual quality scale. PRACTICAL APPLICATION: Food images can be used to assess product shelf life. In the case of fruit salads, the overall visual quality assessed by a trained panel on product images and the percentage of brown pixels in digital images can be exploited to estimate shelf life corresponding to a selected consumer rejection.     

Effect of re-crystallization on tensile, optical and water vapour barrier properties of corn starch films containing fatty acids

Starch films are very hygroscopic and undergo crystallization during processing and storage. In this work, fatty acids (SA, PA and OA) were incorporated into starch films containing glycerol as plasticizer, in order to reduce the hygroscopic character of the films and to improve water vapour permeability. Microstructural, mechanical, barrier and optical properties were studied in both non-stored films and those stored for 5 weeks. Fatty acid addition affected the main properties of films since mechanical resistance was decreased, water vapour permeability was reduced and gloss and transparency were reduced. The degree of starch and FA crystallinity increased with storage time and gave rise to changes in film properties: films became stiffer, less effective as water vapour barriers and less transparent and glossy. Saturated fatty acids were more efficient at reducing WVP as compared to oleic acid, but these differences decreased after storage due to the greater increase in crystallization of the former as it has been observed by X-ray diffraction.     

Bacillus coagulans spore inactivation through the application of oregano essential oil and heat

The present study evaluated the effect of thermal (temperature) and thermochemical (temperature + oregano essential oil (EO)) inactivation of Bacillus coagulans spores in Nutrient Broth (NB) adjusted at 4 °Brix and pH of 4.2. Thermal treatments included temperatures between 95 and 103 °C. For thermochemical treatment, first temperature was fixed at 100 °C and EO concentration varied between 250 and 1000 μg/g. Thermochemical treatment significantly reduced the time needed to reduce a 6 log level of spores compared to thermal treatment, for example around 1.4 min with 400 μg/g of EO. Then, EO concentration was fixed at 400 μg/g and temperature varied between 90 and 100 °C. Although the first results showed a faster spore reduction with 500 μg/g, the fixed EO concentration was 400 μg/g, since it represents a lower organoleptic impact and also a significant reduction in the spores’ resistance. For instance, at 97 °C and 400 μg/g, about 4.3 min was needed to reduce the spores in 6 log, without the EO this time was 5.0 min. These findings indicate that oregano EO may be used to render B. coagulans spores more susceptible to the lethal effect of heat.     

Technological characterisation by free zone capillary electrophoresis (FCZE) of the vegetable rennet (Cynara cardunculus) used in “Torta del Casar” cheese-making

The purpose of this work was to develop a procedure based on protein analysis by free zone capillary electrophoresis (FZCE) that can be used as an alternative to other methods in the determination of the technological quality of vegetable rennet to use in “Torta del Casar” cheese-making. Samples of cardoon flowers (Cynara cardunculus) grouped according to location, harvest year, and ripening stages were used in the study. For the FZCE, a protocol for extracting the methanol-soluble proteins was tested. This method was found to give good repeatability of the corrected migration time (CMT), and showed higher effectiveness in discriminating the technological properties (milk-clotting and casein degradation activities) of vegetal rennets than the SDS–PAGE technique. In addition, three peaks found in the FZCE electropherograms were examined as a good tool to predict the impact of vegetable rennet on the creaminess and overall acceptability of the “Torta del Casar” cheese.