ION LEVELS OF FRESH AND PROCESSED SPINACH USING ION CHROMATOGRAPHY

The anion (Cl^?, NO^?₃, So^2-₄, PO^3-₄, OX^2-) and cation (Na⁺, K⁺, NH4⁺) composition of raw, frozen and canned spinach samples was determined by Ion Chromatography (IC). In general, the levels of these ions were determined after typical food processing operations. Important for its health-related and nutritional point of view is the observation that nitrate levels decreased by about 50% with losses of 15% in total organic nitrogen after typical commercial processing methods.     

RHEOLOGICAL PROPERTIES OF ENZYME SUPPLEMENTED DOUGHS

The rheological behaviour of doughs made with different commercial amylases, xylanases, lipases, and glucose-oxidase, singly and in mixed combinations was investigated. All doughs showed similar trends when subjected to frequency and strain sweep tests. The elastic and viscous moduli increased with frequency, and showed a nonlinear behaviour for strains between 0.2 and 3%. Phase angle presented a maximum at 5 hz in the frequency plot. Resting of doughs decreased complex modulus and increased loss tangent. Enzyme supplementation resulted in softening and weakening of doughs immediately after mixing, and further effects during resting. Pentosan degrading enzymes caused the main changes, and pure lipase preparations the least significant, when compared with unsupplemented doughs. Glucose-oxidase reduced the softening effect of polysaccharide hydrolysing enzymes.     

The COLOR OF WINE: A HISTORICAL PERSPECTIVE. II. TRICHROMATIC METHODS

The trichromatic theory was applied to wines at the end of the 1930s. Trichromatic co-ordinates, dominant wavelength, purity and luminance were determined. The Munsell system and the Lovibond method, which had industrial applicability, were compared with the simplified methods proposed by the L'office Internationale de la Vigne et du Vin (OIV). These methods are official in Spanish food regulations on wine analysis. The CIE recommendations, through the weighted ordinate method, set up the colorimetric parameters for wines, such as hue, lightness, purity or saturation, differences of color, perceptibility. Lately, attempts have been made to correlate the chromatic properties of wines with composition, origin, aging and sensory evaluation. Some authors have studied the reliability of the OIV methods versus the more rigid recent CIE methods. Improved formulae for the computation of dominant wavelength and outstanding correlations among sensorial scores, chromatic parameters and anthocyanins (polyphenols) content of wines have been established.     

Freezing of Banana Slices. Influence of Maturity Level and Thermal Treatment Prior to Freezing

Freezing preservation of banana (Musa cavendishii, var. enana) was investigated. Microwave treatment of banana slices at 650 watts for 2 min or immersion of whole peeled fruits in boiling water for 11 min followed by freezing at -24°C inhibited color deterioration in the frozen product. Treatments showed different effectiveness depending on the enzymatic system studied [polyphenoloxidase (PPO) or peroxidase (POD)] and banana maturity level at the processing date. Blanching in boiling water yielded a good frozen product in which no darkening was observed. The proper stage of ripeness for processing of this banana cultivar was characterized by a firmness of 1.24 kg, a pulp/skin ratio of 1.30 and a green (70%)-yellow (30%) peel color.     

APPLICATION OF MULTIVARIATE STATISTICAL ANALYSES TO THE STUDY OF FACTORS AFFECTING WHITE WINE VOLATILE COMPOSITION

ABSTRACT

The influence of different storage conditions on the volatile composition of young white wine was evaluated during 1 year of storage. The wine was bottled and stored under different conditions of temperature, position and illumination. During storage, a significant increase in total content esters (mainly due to the increase in ethyl butyrate, ethyl acetate and diethyl succinate) and total content acids was detected. Also total content alcohols and carbonyl compounds decreased during storage. Storage time, temperature and illumination have a significant effect on esters content, whereas carbonyl compounds are affected by temperature, and alcohols content is affected by illumination. Stepwise linear discriminant analysis was applied to the experimental data. The results showed that the samples were well classified as a function of storage temperature. On the other hand, a certain trend was observed when the wine samples were classified according to storage time. The samples corresponding to two and four months of storage were well differentiated from the rest.

PRACTICAL APPLICATIONS

From a sensory point of view, the aroma influences greatly the quality of wines. The loss of aromatic characteristics in young white wine, as well as browning, take place over a variable period of time which ranges from one month to several years, depending on wine type and storage conditions. Assessment of possible factors affecting the useful lifespan of young white wine is of great interest for the wine making industry. Knowing the chemical composition of wine, specifically aromas, and its evolution relating to different storage and preservation conditions is an important tool in quality control.     

Patterns of Peroxidase in Ripening Mango (Mangifera indica, L.) Fruits

Chemical and biochemical changes in Lippens and Smith mango cultivars stored at 12°C and 85–90% RH were studied. The observed chemical changes were similar in both varieties. Peroxidase (POD) activity increased in pulp tissues up to the climacteric stage of ripening. In a parallel way, the quantity of extractable proteins decreased from preclimacteric to ripe or senescent fruits. Polyacrylamide gel electrophoresis of the extracts from Smith mangoes revealed three isoenzymes of POD which moved towards the anode at pH 8.3. The isoenzyme pattern of POD of Lippens mango extracts was quite different, showing four faster moving bands in addition to the above mentioned three characteristic bands of Smith mango fruits. Relative activity of the different isoenzymes changed during ripening may provide insight into the ripening process.     

Measuring Meat Homogenate Consistency with the GOSUC Consistometer

The GOSUC consistometer has been tested as a method to follow changes in consistency of meat homogenates. These homogenates did not change consistency during 30 hr storage, increased in consistency when the protein content of the homogenates increased, decreased in consistency when temperature increased and increased in consistency when pH increased over normal pH values of meat. These results show that the GOSUC consistometer could be a useful piece of equipment to detect changes in meat produced by technological processes. When this equipment was used to evaluate the effect of pyrophosphate in meat, it proved that consistency increased when pyrophosphate increased in meat from 0.2 to 0.8%. By using this technique, it has also been shown that freezing increases meat homogenates consistency.     

Cell Wall Composition of Olives

Cell walls of olives (Olea europaea L.), Hojiblanca and Manzanilla, were isolated and fractionated into polysaccharides, and compositions compared. Pectic and hemicellulosic fractions were purified by ion exchange and gel filtration chromatography, and neutral sugar and uronic acid composition determined. Differences occurred between cultivars and seasons: Manzanilla had higher pectic polysaccharides and lower xylans. Hojiblanca showed similar but lesser differences. Arabinans were the main neutral pectic polysaccharides with arabinose > 80%. Homogalacturonans and rhamnogalacturonans were > 50% of the acidic pectic fractions. Degree of esterification and molecular weights were related to extracting solvent. Xyloglucans and galactoglucomannans were neutral hemicelluloses with molecular weights ? 260 kD. Glucuronoarabinoxylans had higher molecular weights (up to 400 kD). Acidic xylans were important in the pulp.     

QUANTIFICATION AND SOME CHEMICAL AND BIOCHEMICAL CHARACTERIZATION OF NITROGENOUS SUBSTANCES FROM VARIETIES OF COMMON BEANS (PHASEOLUS VULGARIS, L.).

Crude protein, extracted protein, and nonprotein nitrogenous substances were quantified in 55 varieties of common dry beans. Crude protein (% N x 6.25) on a dry basis varied from 23.01 to 35.22%, with a mean value of 28.51%. Methionine varied from 0.40 to 1.73% of the crude protein with a mean value of 0.80%. The ratio of globulin/albumin ranged from 1.00 to 3.31. Thirty percent of the total nitrogen was of low MW and was lost in the dialysis (MW cut off 8,000 daltons). Electrophoretic patterns (PAGE) revealed from 3 to 11 bands in the globulin fraction and 4 to 11 in the albumin fraction. Trypsin and chymotrypsin inhibitory activity was much higher in the albumin fraction than in the globulin fraction. The globulin fraction from most of the varieties was more inhibitory against trypsin than chymotrypsin. On the other hand, in the albumin fraction of the majority of the varieties the activity was stronger against chymotrypsin. Hemagglutination titer for 57 varieties ranged from 1024 to 32. Eight varieties had titers of 1024 and only four had titers of 32.