A study was conducted to identify the volatile compounds in aged Iberian hams, processed in the traditional way. The volatiles from aged hams were entrained in cold traps after distillation under high vacuum. The distillate was collected with dichloromethane and analysed by gas-chromatography-mass-spectrometry (GC-MS). Seventy-seven compounds were tentatively identified in the volatile fraction. Alkanes (12), branched alkanes (14), aldehydes (13), and aliphatic alcohols (9) dominated the volatiles. Small amounts of lactones (5), esters (9) and ketones (7) and other miscellaneous compounds were also present. The possible origins of these compounds and their relationship with the characteristic flavour of this product are discussed. © 1991.

    The formation of heat-induced gels from bovine serum albumin (BSA) and β-lactoglobulin (β-Lg) under different conditions was studied. The minimum protein concentration required for formation of self-supporting gels in 100 mm Tris-HCl buffer (pH 8·0) following heating at 90°C for 15 min was 4% for BSA and 5% for β-Lg. Maximum gel hardness for both BSA and β-Lg occurred at pH 65. The hardness of β-Lg gels reached a maximum with the addition of 20-40 mm NaCl or 2 mm CaCl , while BSA was at a maximum with 5 mm CaCl but were unaffected by NaCl. The hardness of β-Lg gels decreased slightly upon addition of various anions of sodium (between 50 and 100 mm). The effects followed the lyotropic series. Addition of N-ethyl-maleimide (NEM) decreased gel strength of BSA, while the gel hardness of β-Lg increased slightly with 5 mm NEM but decreased at higher NEM levels. Dithiothreitol (DTT), at 5 and 2 mm, respectively, enhanced gel hardness of BSA and β-Lg gels. Higher DTT levels significantly decreased gel hardness for both BSA and β-Lg. These results indicated that disulfide bonds are important in BSA gels, while electrostatic interactions and disulfide bonds are involved in the formation and maintenance of β-Lg gels. © 1991.

    The β-carotene contents of forty vegetables and fourteen fruits were determined using the AOAC open-column (magnesia and Hyflo Super Cel mixture) chromatographic method and compared with a newly developed reverse-phase HPLC method, in which carotenoids were separated isocratically on an octadecylsilane (C ) column using a ternary mixture of acetonitrile, methanol and ethyl acetate. Results obtained showed that the AOAC method gave falsely elevated results for samples containing α-carotene, as well as those with very low β-carotene concentrations. On the other hand, the HPLC method successfully separated and quantitated the major carotenoids present; namely, lutein, cryptoxanthin, lycopene, γ- and α-carotenes in addition to β-carotene. The carotenoid composition of most of the green vegetables was rather consistent, comprising only lutein and β-carotene. In contrast, there was no clear pattern of carotenoids present in the other vegetables and fruits, where several other carotenoids were detected in varying proportions. The vitamin A activity, expressed as μg of retinol equivalent (RE), was calculated on the basis of all pro-vitamin A carotenoids (cryptoxanthin, γ-, α- and β-carotenes) detected. Most of the green leafy vegetables, including several local vegetables, had high RE. Several green non-leafy and other vegetables were found to have low and medium RE. None of the fruits studied may be said to have high vitamin A activity. RE calculated on the basis of results from the AOAC method was found to be erroneously low for samples with significant proportions of pro-vitamin A carotenoids other than β-carotene, and falsely elevated for those with α-carotene. Total carotenoid concentrations can be estimated by taking absorbance readings of sample extracts directly in a spectrophotometer or by the HPLC method. The study clearly shows that the HPLC method would give a more complete picture of the carotenoid composition as well as a more accurate quantitation of the vitamin A value of the vegetables and fruits. The nutritional significance of the findings is obvious since these foods are important sources of vitamin A for the majority of the communities in the country. © 1991.

    The 2-thiobarbituric acid (TBA) test for the measurement of lipid oxidation was discovered over 40 years ago. Since then it has been widely used for the measurement of the oxidative state of biological and food materials. Despite copious literature references and its widespread usage there are still uncertainties over the exact chemistry of the reaction and its applicability. This review attempts to draw together the relevant publications and discuss the merits of the TBA test, particularly in the analysis of foods. © 1991.

    Dietary fibre (DF) determinations were carried out on grape pomaces by AOAC and spectrophotometric procedures. Insoluble dietary fibre (IDF) and Klason lignin (KL) residues contained appreciable amounts of condensed tannins (CT) and resistant protein (RP). The presence of CT and RP in the residues obtained after the successive action of amylase, protease and amyloglucosidase and chemical treatments with H SO and HCl-triethyleneglycol, together with similar data previously reported for other samples could be considered in a wider definition of the DF complex as 'indigestible polysaccharides, phenolic polymers and resistant protein'. The term 'phenolic polymers' includes both lignin and CT. © 1990.

    Grain samples of six varieties of common millet (Panicum miliaceum), three varieties of finger millet (Eleusine coracana) and four varieties of foxtail millet (Setaria italica) were analyzed for their proximate composition, mineral composition and phytate and oxalate contents. The average protein contents of common millet, finger millet and foxtail millet were 14·4, 9·8 and 15·9%, respectively. The crude fibre content of the millets ranged from 3·2 to 4·7%. In general, the mineral contents were high compared with those of other common cereal grains. In particular, the high level of calcium (0·24%) in finger millet was noteworthy. The high contents of phytic acid (0·50-0·70%) in millets present grounds for concern, in view of its interference with several minerals. The oxalate contents (21-29 mg/100 g dry weight) of the millets were low. Considerable between- and within-millet differences were observed with regard to most nutrients analyzed. The overall results are suggestive of the underexplored potential of millets as sources of dietary nutrients. © 1990.

    The proposed method includes analysis of the serum obtained after suitable sample dilution and Carrez addition followed by 12 000 rpm centrifuging for 2 h by HPLC, using a reverse-phase C18 column and an ultraviolet detector operating at 285 nm in isocratic elution with 90:10 water-methanol. Juice and paste (double and triple) samples have been analysed by means of two methods (Winkler and HPLC) and statistical analysis, carried out on the results, clearly shows a difference between them. In particular, the colorimetric method which includes no centrifuging, but only filtration, almost always yields results which are lower than the HPLC ones. © 1990.

    

    Changes in cyanidin-3-glucoside, cyanidin-3-rutinoside, malvidin-3-acetylglucoside, total anthocyanins, percent polymeric color and browning indexes in stored lychee (Litchi chinensis Sonn.) fruits were determined. Total anthocyanin content declined from 1·77 to 0·73 mg/g fresh weight, and individual anthocyanins also decreased throughout the 48-day storage period. Decline in anthocyanins was accompanied by an increase in browning. Polymeric pigments also gradually increased from 20·9 to 53%. © 1991.

    The paper refers to the determination of benzo(a)pyrene (BaP) contents in smoked fish by an HPLC method. Samples were analyzed after saponification and purification on Florisil and Separon SGX C-18, using selective fluorescence detection for the determination of BaP in smoked fish as well as in the model system, which was kept at the same conditions. In the model system, the BaP degradation was found to be directly proportional to the duration of influence of environmental physicochemical factors with a clearly linear BaP decay line. On the other hand, in the case of smoked fish the BaP contents were changed in dependence on diffusion into the internal product layers where their amount was relatively stabilized due to the absence of both light and oxygen. Measurements have shown that BaP contents cannot be considered as a constant but that a gradual decrease is taking place as a result of various factors influencing the degradation process, which in itself can attain different velocities depending on the changing properties of the meat products as well as on environmental conditions.

    This communication reports the occurrence of five heterocyclic disulphides in the headspace volatiles from beef, three of which have not been reported previously in meat. Evidence is presented which indicates that two of these compounds contribute to the desirable aroma of cooked beef. © 1991.

    In recent years, there has been particular emphasis on obtaining more accurate data on the types and concentrations of various carotenoids and retinoids in foods for various health and nutrition activities. A great deal of attention has thus been given to improved methodologies for the study of these two groups of compounds. This review is aimed at defining the state-of-the-art of analytical methods for the study of carotenoids and retinoids, particularly in foods and blood samples. The first part of the review discusses various preliminary sample treatment procedures, including precautions to be taken during handling of samples. The greater part of the discussion is devoted to reviewing the various methods reported for the separation and quantitation of these two groups of compounds. A pre-requisite in the analysis of carotenoids and retinoids is preliminary sample treatment in order to release, isolate and extract the compounds of interest from the food matrix. Numerous different preliminary treatment procedures have been reported in the literature. In general, however, these procedures follow a few basic steps, upon which various modifications have been made. For convenience, the treatment procedures for plant materials, animal foods and blood samples are separately treated in this review. Because of the unstable nature of the carotenoids and retinoids, especially towards light, heat, oxygen and acids, various precautions have to be taken during saponification, extraction and chromatography steps of the analytical procedure. Precautions against oxidation, such as the use of antioxidants, protection against exposure to direct light, and proper storage of solutions are discussed. After sample extraction, most investigators endeavoured to separate the carotenoids and retinoids from interfering substances in order to obtain more accurate results. A wide variety of separation and detection and quantitation procedures have been used in studies of these compounds. There has been a general trend in the change of these methodologies over the last two decades. An early technique used for the separation of carotenoids in plant materials, mainly in the 1960s, was countercurrent distribution. A few early studies using paper chromatography were also reported. In the 1970s, a few studies of carotenoids and retinoids using gas-liquid chromatography and gel-permeation chromatography were encountered. A number of studies employing thin-layer chromatography (TLC) as a single technique for the separation of carotenoids in plant materials were encountered throughout the 1970s and the early 1980s. TLC was also used by several investigators in combination with other separation techniques. The procedure was less widely used in studies of retinoids. Adsorption (open) column chromatography, utilizing primarily descending, gravity-flow columns, was widely used for the study of carotenoids and retinoids in foods, even in the 1960s. The procedure remained very much in use in the 1970s and 1980s. Commencing from the late 1970s, a new chromatography procedure became more prominent in the literature. High-pressure liquid chromatography has become a widely used procedure for the separation of carotenoids and retinoids in various materials. Owing to the complicated nature of the required analysis, the associated methodologies are still being developed and improved. Used together with adsorption column chromatography and UV-vis spectroscopy, especially during method development stage, HPLC would be the method of choice for arriving at more accurate data on the content and composition of carotenoids and retinoids in foods. © 1991.

    Phenolic compounds, which are present in significant amounts in virgin olive oil, are almost completely destroyed during the refining process of the oils. Numerous phenolic acids were found in oil samples and caffeic, p-coumaric, syringic, vanillic, ferulic, protocatechuic and p-hydroxybenzoic acids have been identified. Among these, p-coumaric acid was predominant in all virgin olive oil samples. They can play important roles as antioxidants and influence the flavour of the oil. © 1990.

    The binding of calcium by different milk proteins and the effects of heat were investigated. The influences of calcium and lactose were also investigated. It was shown that the caseins of cow's milk have a high calcium binding capacity, when treated with calcium at 25°C for 30 min, pH 7·00, due to the high number of calcium binding sites. The order of binding capacities is α -casein > β-casein > κ-casein. For whey proteins the order is β-lactoglobulin (β-lg) > α-lactalbumin (α-la). Lactose, in general, when present at 25°C, did not appreciably affect the calcium binding of the major milk proteins. Heating of whole casein at 80 or 95°C for 30 min caused conformational changes of the protein resulting in an increase in its calcium binding ability. The presence of lactose during heating with or without calcium reduced its calcium binding. The calcium binding of α -casein was not affected by heating, throughout the temperature range studied, either in the presence or in the absence of calcium, an indication that α -casein may undergo physical changes at high temperatures, but the accessibility and/or the number of calcium binding centres are not increased. β-Casein, when heated with calcium, was subject to conformational changes which were reflected in changes in the degree of calcium-binding. Heating of β-lg in the presence of calcium did not much affect the amount of calcium bound to it. However, in the absence of calcium an increase of 21·5% in calcium binding was observed after heating at 80°C and a decrease of 40·0% after heating at 95°C, compared to unheated samples. © 1991.

    The information available on the nutritional value of the meat of the one-humped camel (Camelus dromedarius) is very limited. The mineral elements and proximate composition of muscle tissues taken from the shoulders, thighs, ribs, necks and humps of seven young (1-3 years) male camels have been determined. The amounts of mineral elements, protein and ash in the various muscle tissues of the camel are generally similar to the amounts reported for these constituents in the corresponding tissues of beef. However, the meat of the camel contains significantly less lipids (1·2-1·8% versus 4·0-8·0%) and higher water content (5-8% more) than beef. The hump consists mainly of lipids (86·9%). © 1991.

    Phosphorylation with POCl (in the absence and presence of essential amino acids) could be a promising tool for improving functional and nutritional properties of food proteins (e.g. yeast protein, zein, soybean protein). The amount of phosphorus covalently bound to proteins can reach up to 3·9%, but is usually in the order of 1-2%. The in-vitro digestibility of food proteins phosphorylated with POCl is not adversely affected. The in-vivo digestibility (using the Tetrahymena thermophili bioassay) has been studied only in two cases (casein and zein). While digestibility was not affected in the case of casein, the growth rate of the microorganism showed an 11-fold improvement on modified zein (phosphorylated in the presence of limiting amino acids) over that of the original zein. Phosphoproteins are abundant in nature and some, e.g. milk casein, egg white albumin, egg yolk phosvitin, are part of the regular human diet. Experiments with animals are necessary to determine the digestion of proteins phosphorylated with POCl by mammals, and to study the introduction of potentially toxic residues into the proteins that may prevent their direct utilization in foods. © 1990.

    The contents of low molecular mass phenols and caffeine have been analysed in five samples of beans and the associated pulp, derived from two species of coffee and two associated hybrids. The composition of the coffee beans was consistent with previous reports. The pulp contained smaller quantities of the same caffeoylquinic acids, feruloylquinic acids and dicaffeolyquinic acids as the beans, but caffeoylferuloylquinic acids were not found even in the pulp from a robusta coffee. Pulp from a robusta coffee had a lower caffeine content than the pulp from two arabica cultivars, the reverse of the situation existing in the beans. A significant component in all pulp samples was isolated and identified as protocatechuic acid. © 1991.

    A method for the fractionation of sodium caseinate into a β-casein-rich permeate and an α κ-casein-rich retentate has been developed using ultrafiltration through 300 000 dalton cut-off membranes at 4°C. The β-casein fraction was 80% homogeneous, γ-caseins being the principal contaminants; most of the β-casein could be recovered in the permeate by diafiltration or repeated ultrafiltration. For the successful recovery of β-casein, it was essential to dissolve the sodium caseinate in deionized or distilled water but pH in the range 7-9 was not significant. A caseinate concentration of 1% was optimal in terms of yield and ease of operation. © 1990.

    Changes in the fractions of the pectic substances in carrots were studied after blanching, dehydration and blanching plus dehydration. The water-soluble pectin and EDTA-soluble pectin fractions were studied after ion-exchange chromatography. A different pattern of uronic acids from the column and a different degree of esterification and neutral sugar composition indicated significant changes in both pectic fractions, especially in the EDTA-soluble pectin with the appearance of a new large fraction which had not been there previously. The significant decrease in the total percentage of all the pectic substances after dehydration alone, compared with the decrease caused by blanching plus dehydration, led to the conclusion that controlled blanching contributes to reducing the changes in pectic substances. © 1990.

    The edible fruit tissue of the chebulic myrobalan (Terminalia chebula Retz.) was analyzed for certain organic and mineral nutrients. Compared with commercial apples the tissue contained 10·3 and 14·5 times more vitamin C and protein, respectively. Of the 14 macro- and micro-nutrients studied, the minimum Recommended Dietary Allowance (RDA) for Se, K, Mn, Fe and Cu can be met (100, 63·5, 32, 30 and 28·5%, respectively) if 100 g of the raw fruit is eaten. Aspartic acid, glutamic acid, arginine, proline and lysine constituted 39·6, 8·6, 6·7, 6·4 and 5·0%, respectively, of the total amino acids. These results demonstrate that the chebulic myrobalan is highly nutritious and could be an important source of dietary supplement in vitamin C, energy, protein and mineral nutrients. © 1991.