EFFECT OF STORAGE PERIOD AND EXPOSURE CONDITIONS ON THE QUALITY OF BOSANA EXTRA-VIRGIN OLIVE OIL

Changes in quality parameters, antioxidant compounds, oxidative stability and antioxidant activity during 18 months of storage of a monovarietal extra‐virgin olive oil from Bosana cultivar , and exposed to light and dark, were studied. Analysis of data showed that all the parameters underwent significant changes during storage: free acidity, peroxide and ultraviolet (UV) spectrophotometric indexes remained below the limits reported in the EEC Regulations 2568/91 and 1989/03 , and these are: ≤0.8% for acidity, ≤20 meq O₂/kg for peroxide and ≤2.50 and ≤0.22 for K232 and K270, respectively. Phenol andα‐tocopherol content decreased during storage (42.0 and 29.6%, respectively) while chlorophylls and carotenoids underwent a decrease until 8 months of storage (49% and 30%, respectively); after that, the values remained constant. Oxidative stability and antioxidant activity had not changed dramatically during 18 months. Phenols were significantly correlated to the antioxidant activity of the oil, while oxidative stability measured by Rancimat did not show any correlation with carotenoids, chlorophylls, phenols andα‐tocopherol. Regarding exposure conditions, storage in the dark was better in retaining the quality of the oil, as expected.     

PRESERVATION OF CABERNET SAUVIGNON GRAPE MUST SAMPLES DESTINED FOR CHEMICAL ANALYSIS: ADDITION OF SODIUM AZIDE, ALLYL ISOTHIOCYANATE, OCTANOIC ACID AND ETHYL BROMOACETATE, AND EFFECT OF PASTEURIZATION

Grape must samples destined for chemical analysis can usually be preserved just for a short period of time. As a consequence of the addition of antifermentative substances, or heat treatment, the analytical parameters of must may change. In this work, five different methods of inhibiting endogenous yeast and bacteria in Cabernet Sauvignon grape must were studied. Sodium azide (NaN₃), allyl isothiocyanate, octanoic acid and ethyl bromoacetate were added to samples at various concentrations, and samples were pasteurized by three different methods. The effects of treatments were monitored with respect to soluble solids content, malic (H₂M) and tartaric (H₂T) acids, pH and the titratable acidity of samples. Allyl isothiocyanate and ethyl bromoacetate (100 mg/L) preserved samples for 6 months, NaN₃ did not prevent the degradation of H₂M and H₂T and pasteurization of sample and octanoic acid did not preserve the samples.     

DISCREPANCIES AND CONSISTENCIES IN THE SUBJECTIVE RATINGS OF WINE-TASTING COMMITTEES

Tasting committees issuing subjective scores carry out the evaluation of wines, as for many other food products. Since highly qualified experts form wine‐tasting committees, the reliability of the scores is not generally questioned. Nevertheless, statistical methods can be applied to assess the work of tasters from the point of view of concordance. Agreement degree may be used as a measurement of the reliability of subjective rating. In order to evaluate both the extent of agreement as well as the circumstances that produce disagreement, this paper examines the subjective scores assigned to white wines awarded the Rias Baixas (Spain) denomination of origin certificate using statistical analysis. It will be seen that agreement depends significantly on the variability in scoring. A statistical method is proposed, which permits an appraisal, in terms of consistency and reliability, of the committees that evaluate wines for quality and authenticity.     

ANTIOXIDANT ACTIVITY COMPARISON OF THOMPSON GRAPE POMACE EXTRACT, ROSEMARY AND TOCOPHEROLS IN SOYBEAN OIL

The effect of natural antioxidants was tested by oxidative stability index (OSI) in refined soybean oil (RSO) using Rancimat method. Phenolic compounds of Thompson grape pomace were extracted with 95:5 (v : v) ethanol : water. The antioxidant activity of grape pomace extract (GPE) obtained was compared with those of rosemary extract (RE), and tocopherols mix (TM) known as covi-ox T-70. The synergistic effect of citric acid was also evaluated. Results showed a total phenols content of 17.39 mg ( + )-catechin equivalents per g of GPE. Thompson GPE at 0.3 and 0.5% (w/w) exhibited greater antioxidant activity than TM. RSO containing GPE or RE at 0.5% (w/w) showed an OSI higher than 48 h at 110C. Citric acid did not show synergistic effect with GPE. However, a synergistic effect for TM at 0.02% (w/w) with citric acid at 1.0% (w/w) was observed. Citric acid at 2.0% (w/w) with RE at all concentrations tested also displayed synergism.

PRACTICAL APPLICATIONS

Synthetic antioxidants are widely used in the food industry to delay fat oxidation; however, their utilization has been questioned due to toxicology concerns. Researchers have recognized the need to identify new natural antioxidants to use as additives. In this study, we measured total phenolics content of Thompson grape pomace extract (GPE) and found that the antioxidant activity of this extract was stronger than tocopherols from soybean oil. We propose that GPE can have applications as a food antioxidant.     

Rapid Methods for Lipoxygenase Assay in Sweet Corn

Potential methods for rapid assay of sweet corn lipoxygenase (LPO) were evaluated and compared by visual inspection. Both model system (partially purified) and vegetable (LPO extract) system studies were carried out. Model system studies indicated that LPO had maximum activity at pH 6.0 and 2.0 mM linoleic acid. Methylene blue bleaching (MBB), carotene bleaching (CB), and potassium iodide-starch (KI-S) methods were evaluated both spectrophotometrically and visually. Both MBB and KI-S methods were effective for the model system. For the vegetable LPO extract systems (sweet corn and green beans), the MBB method indicated positive results for both, the CB method was not effective for either, and the KI-S method was very effective for green beans but not for sweet corn.     

Wear behaviour of an aluminium matrix composite

The wear behaviour of a composite material consisting in AS12UNG alloy reinforced with 15% short fibres of alumina has been studied. The material composition and the wear test conditions were defined in order to evaluate the potential performance of automotive pistons produced with such composite composition. As initially expected, the results indicate that an increase in the sliding velocity lead to higher wear rates in the stationary stages, and higher applied loads also induced acceleration in the wear process. Also, reciprocating sliding movement is clearly more damaging than the circular. However, results have shown that wear rates at 150 °C are lower than those recorded at room temperature representing a promising result for the use of this material in components that operate in this condition. This advantageous behaviour is lost at temperatures near to 300 °C, when a marked increase in the wear rate and a signification contribution of adhesive wear were observed.     

Potassium Sorbate Permeability of Methylcellulose and Hydroxypropyl Methylcellulose Coatings: Effect of Fatty Acids

Surface microbial stability is a major determinant of the shelf life of refrigerated meat products. Surface microbial growth has also been noticed in intermediate moisture foods exposed to temperature fluctuations. One solution to this problem is to apply edible coatings to the food surface which control diffusion of antimicrobial agents into the food. Films with such properties were identified using a permeability cell. Methyl- and hydroxypropyl methylcellulose mixed with lauric, palmitic, stearic and arachidic acid significantly lowered the potassium sorbate permeation rate relative to cellulose ether films containing no fatty acids. Permeability determinations at 5, 24, 32 and 40°C showed excellent agreement with the Arrhenius activation energy model for the permeation process.     

Dihydrocapsaicin Oxidation by Capsicum annuum (var. annuum) Peroxidase

Oxidation of dihydrocapsaicin (8-methyl-N-vanillyl-6-nonanamide) by peroxidase (EC 1.11.1.7) from Capsicum annuum var. annuum fruits yielded one absorbent oxidation product with E₂₆₂= 4.7 10³ M^?1 cm^?1. Dependence of oxidation rate on dihydrocapsaicin and H₂O₂ concentrations revealed Michaelis-Menten type kinetics with inhibition at high substrate concentrations and optimal pH near 6.0. Dihydrocapsaicin was oxidized by pepper peroxidase, and participation of peroxidase in capsaicinoid metabolism of pepper fruits should be taken into account.     

Glucose Oxidase/Cqtalase Improves Preservation of Shrimp (Heterocarpus reedi)

The preservative effect of glucose oxidase (GOX) and catalase (CAT) in a 4% glucose aqueous solution were evaluated on shrimp (Heterocarpus reedi) stored at 0–2°C. On-board and immediately after catch, shrimp were washed with tap water at 10°C, and dipped or kept in the enzyme solution. Microbial (total psychrotrophs and Pseudomonas spp. counts), chemical (total volatile bases, ammonia and pH) and sensory tests (whole-raw and cooked-peeled samples) showed that holding shrimp in the GOX/CAT/glucose solution retarded microbial spoilage and preserved quality more effectively than dipping shrimp in the same solution. The importance of treating shrimp as early as possible was demonstrated by comparing shrimp treated 4 and 82 hr after catch.