Changes in nitrogen content and amino acid composition of navel oranges during ripening

Nitrogen content and composition of amino acids in juice and rind of navel oranges were studied. The compared varieties were ‘Navelina’ ‘Washington Navel’ and ‘Navelate’, early, mid-season and late types, respectively. Total N content in juice increased during the season with values from about 60 to near 100 mg 100 ml^?1 in Navelina and ‘Washington Navel’ and from 60 to about 80 mg 100 ml^?l in ‘Navelate’; amino N increased from 30 to 60 mg 100 ml^?lapproximately in the three varieties. The total N content in rind was quite similar in all cases, with values that decreased with time from 1 to around 0·6 g 100 g^?l dry weight (DW), 50–60% corresponding to the protein N. The main free amino acids in juice and rind at different maturity stages are tabulated. Proline represents at maturity around 50% of the total free amino acids in rind, with values near to 1·5 mmol 100 ml^?l in juice and over 5·0 mmol 100 g^?1 DW in rind. Total protein amino acids in rind decreased during maturation, reaching final values of about 20 mmol 100 g^?1 DW. Differences in composition among the three studied varieties are discussed.     

Chemical Evaluation of Musa ‘Bhimkol’ as a Baby Food

The edible pulp of Musa ‘Bhimkol’ was analysed for certain organic compounds and mineral nutrients at two stages of development of the fruit to evaluate it as a baby food. Energy value and carbohydrate concentration increased substantially as the fruit ripened so that 16.8% of the energy requirement (recommended daily allowance, RDA) for six-month-old infants would be met by 100 g of the fresh pulp. Although vitamin C content decreased at maturation, 7% of the RDA would be provided by 100 g fresh pulp. The fruit was found to be very rich in macro- and micronutrients, and 100% of the six-month infants RDA for K, Mn, Zn and Se would be satisfied with 100 g of fresh pulp. This amount of pulp would also provide 86%, 57%, 24% and 12% respectively of the Mg, Cu, Fe and P RDA. P and Mg were found to be more highly concentrated in the ripe than in the unripe fruit whereas the reverse was the case for Ca and Se. Aspartic acid, glutamic acid and leucine were the major amino acids in the ripe fruit and respectively constituted 13.1, 12.5 and 7.9%, of the total. The concentration of essential and non-essential amino acids was much higher than that in a commercial banana. Twelve of the 17 amino acids analysed were more concentrated in the mature compared with the green fruit, and 11 of these were an order of magnitude higher than in M paradisiaca L banana. The results of the present study demonstrate that Musa ‘Bhimkol’ is a nutritious baby food.     

Fatty Acid Composition of ‘Cerrado’ Seed Oils

The seeds of 28 species from ‘cerrado’, a typical savanna ecosystem of Brazil, were analysed for total lipid contents and fatty acid distribution. The seeds of 10 species presented contents above 150 g kg⁻¹, the highest yield reaching 335 g kg⁻¹. Distribution of fatty acids based on polyunsaturated compounds seems to be rare in seed oils from ‘cerrado’: only three seed oils were found to be based on linoleic acid and none on linolenic acid. Eight seed oils, four of them Fabales, presented palmitic acid as a dominant constituent. Half of the species presented oleic acid based seed oils. Two species stand out for unusual fatty acid distribution: Qualea grandiflora (Vochysiaceae) with 171 g kg⁻¹ of seed oil presenting 723 g kg⁻¹ of lauric acid and Serjania erecta (Sapindaceae) with 256 g kg⁻¹ of seed oil presenting 623 g kg⁻¹ of eicosenoic acid.     

Characterisation of ‘Starking’ apple polyphenoloxidase

Experiments were performed to optimise the extraction conditions of ‘Starking’ apple fruit polyphenoloxidase (PPO), to evaluate the affinity and specificity towards several substrates and to study the stability of enzyme extracts from apple samples stored under different conditions. Sodium phosphate buffer (0·2 M , pH 6·5) plus 0·25% Triton X₁₀₀ and 1% or 2% PVPP was found to be the most efficient extraction medium. Chlorogenic acid, dopamine and 4-methylcatechol showed similar specificity towards PPO, and chlorogenic acid was found to be the best substrate for the enzyme. Enzyme extracts from frozen cut apple stored at −4°C, and extracts from lyophilised apple samples stored at 4°C were more stable than extracts obtained from fresh-cut or acetone powder samples. © 1998 SCI.     

Reduction in hydroxymethylfurfural content in ‘churros’, a Spanish fried dough,by vacuum frying

This work explores the advantages of vacuum frying of ‘churros’, a Spanish dough pastry, compared to standard deep‐fat frying. Oil uptake, texture change, colour development, nonenzymatic browning and hydroxymethylfurfural (HMF) concentration were analysed at different frying conditions. The results obtained during vacuum frying at 100, 120 and 140 °C and 21 kPa were compared with those obtained at atmospheric pressure at 140 and 180 °C. For the same final water content, the vacuum fried ‘churros’ showed no significant differences in the fat uptake compared to those fried at atmospheric pressure (P > 0.05). However, the vacuum fried dough had a much crunchier texture. The evolution of the CIELab a* coordinate and the browning measurement at 280 nm show that vacuum frying is able to slow down the development of browning tones. Furthermore, products can be obtained with an HMF content <1 mg kg^?1 of dry dough.     

Determination of 4‐ethylcatechol in a Merlot wine using sensory evaluation and the electronic tongue

The objective of this study was to determine the influence of 4‐ethylcatechol (4‐EC) on the sensory profile of Brettanomyces‐contaminated Merlot wine and evaluate electronic tongue discrimination. Using sensory evaluation panels, the consumer detection threshold (DT) and the consumer rejection threshold (CRT) of 4‐EC were determined in Merlot containing 493, 714, 1035 and 1500 μg L^?1 4‐EC. The DT of 4‐EC in Merlot was 823 μg L^?1, while the CRT was 1323 μg L^?1. The electronic tongue discriminated index (DI = 82%) among the samples, with hierarchical clustering showing a clear distinction between the control sample and the spiked samples. The lowest concentration distinguished by the electronic tongue was 493 μg L^?1, a lower value than the sensory threshold determined. These findings suggest that for the detection of 4‐EC in Merlot, the e‐tongue may be more sensitive than some consumers and the e‐tongue may be a suitable methodology for detection of subthreshold concentrations of chemical compounds in wine.     

Maillard reaction during the processing of ‘Doce de leite’

‘Doce de leite’, a dairy product widely consumed in Brazil as a dessert or cake filling, is obtained from the heat treatment of milk and sucrose. On heating, the Maillard reaction occurs with the formation of desirable brown-coloured products with a characteristic and pleasant flavour. However, the reaction can also lead to changes in nutritive value. In order to follow chemically the extension of the Maillard reaction and its effect on the nutritive value of ‘doce de leite’ its commercial processing was followed. Increases in the level of free 5-hydroxymethylfurfural and in absorption at 420 nm by pigments attached to the protein were observed. The amino acid analysis showed a significant decrease in lysine levels (33%) as well as in arginine (11%) and histidine (10%). There was also a reduction in available lysine levels, as measured by the fluorodinitrobenzene (50.6%) and by the 2,4,6-trinitrobenzenesulphonic acid (23.5%) methods. These results suggest a deleterious effect of the processing of ‘doce de leite’ on the nutritive value of the milk.