Triacylglycerol Species of Less Common Edible Vegetable Oils

Chromatographic and spectroscopic methods used for the detection and quantification of triacylglycerol (TAG) species present in less common edible vegetable oils (almond, hazelnut, pumpkin seed, safflower, sesame, walnut, and wheatgerm oils) are reviewed. For these oils, as well as for thistle oil and high-oleic sunflower oil, for which no data exist on their TAG composition, both high-performance liquid chromatography (HPLC) and gas chromatography (GC) chromatographic plus spectrometric techniques have also been performed. Triacylglycerol comparison of the data found in the literature is also presented. Five fatty acyl moieties (palmitoyl-, stearoyl-, oleoyl-, linoleoyl-, and linolenoyl-) are found to mainly contribute to the formation of TAG species of the aforementioned edible vegetable oils, whereas six more (palmitoleoyl-, arachidoyl-, gadoleoyl-, heptadecenoyl-, margaroyl-, and erucoyl-) are reported as minors. Only 19 to 33 TAG make up the mass of these oils. These TAG are also found in most common edible oils, thus indicating a “uniformity” in the minor and main TAG composition of edible vegetable oils. Trioleoyl-glycerol predominates in almond (13.3-48.6%), hazelnut (35.3-57.9%), and high oleic sunflower (44.2% and 52.9%) oils, trilinoleoyl-glycerol in safflower (40.1-49.7%), thistle (36.9% and 46.0%), walnut (25.9-38.1%), and wheatgerm (15.7-33.0%) oils. Sesame and pumpkin seed oils are rich in dioleoyl-linoleoyl-glycerol (5.9-17.5%, 9.5% and 18.6%, respectively) and oleoyl-dilinoleoyl-glycerol (8.0-18.7% and 12.8-21.1%, respectively).     

Microflora of the sour dough of wheat flour bread IX. Biochemical characteristics and baking performance of wheat doughs elaborated with mixtures of pure microorganisms

Summary Changes in mono- and disaccharides and acetic and lactic acid production of six different straight doughs elaborated with combinations of pure strains of yeastsSaccharomyces cerevisiae andCandida boidinii and lactic acid bacteriaLactobacillus plantarum andStreptococcus sp have been investigated, as well as the baking quality of the resulting breads. The type and proportion of the fermentative microorganisms were found to influence the biochemical activity of the doughs. The sugar levels after mixing reached different proportions, depending on the type of sugar and the type of microorganisms used. After proofing, the glucose and fructose content of the doughs decreased to 0.01%–0.02% db and maltose decreased to 0.45%–0.11 % db. Acetic and lactic acids underwent variable changes during fermentation, depending on the type of dough. Lactic acid showed higher levels than acetic acid. Bread made from these doughs had different sensory characteristics, texture, edibility and overall acceptance, as well as different lactic and acetic acid contents, depending on the mixture of microorganisms inoculated.

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Biochemische Merkmale und Leistungsfahigkeit der mit Mischungen reiner Mikroorganismen hergestellten Weizenbackteige

Zusammenfassung Die Forschungsaufgabe befaßte sich mit den Veranderungen der Mono- und Disaccharide, mit der Entstehung von Essig- und Milchsaure in sechs Teigen, die mit Kombinationen reiner HefekulturenSaccharomyces cerevisiae undCandida boidinii und MilchsäurebakterienLactobacillus plantarum undStreptococcus sp hergestellt waren und mit den sich daraus ergebenden Qualitätsmerkmalen der Brote. Die Art und Anteile der Mikroorganismen übten einen entscheidenden Einfluß auf die biochemische Aktivität der Teige aus. Nach dem Knetvorgang konnten unterschiedliche Gehalte gemäß der eingesetzten Saccharide und Mikroorganismen festgestellt werden. Der Glucose- und Fructoseanteil der fermentierten Teige verringerte sich auf 0,01–0,02% t. g., der Maltoseanteil auf 0,45-0,11% t.g. In den einzelnen Teigen veranderten sich wahrend der Garung die Essig-und Milchsauregehalte unterschiedlich. Bei der Milchsaure konnte eine grbBere Zunahme und somit höhere Endgehalte als bei der Essigsaure festgestellt werden. Die mit diesen Teigen hergestellten Brote erreichten verschiedene Textureigenschaften (Weichheit der Krume) und sensorische Merkmale, insbesondere Kaufahigkeit und Geschmack Bowie einen, entsprechend der Mikroorganismenmischung, höheren oder geringeren Milch- und Essigsäuregehalt.

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Presented at the 8th International Cereal and Bread Congress, Lausanne, Switzerland, June 1988.

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This paper is a part of a doctoral thesis     

Characterization of synthetic hydrocalumite-type [Ca2Al(OH)6]NO3·mH2O: Effect of the calcination temperature

A lamellar hydrocalumite-type [Ca₂Al(OH)₆]NO₃·mH₂O, (HC), was synthesized and characterized by X-ray diffraction analysis (XRD), surface area, pore size measurements, CO₂-Thermal Programmed Desorption, and later tested as catalysts in the double bond isomerization of 1-butene. The layered structure of HC collapses above 523 K yielding an amorphous material at 573 K which upon calcination at 873–973 K transforms into a mixture of CaO and mayenite Ca₁₂Al₁₄O₃₃. The calcination temperature has a marked effect in the formation of basic sites. Thus for example, HC calcined at 1073 K shows 90% of strong basic sites (CO₂ desorption at 1023 K) while they are absent in HC calcined at 573–673 K. HC calcined at 973 K shows high catalytic activity (74% conversion) in the isomerization of 1-butene without any appreciable deactivation after 4 h on stream.     

Viability assessment of lactic acid bacteria in commercial dairy products stored at 4 °C using LIVE/DEAD® BacLightTM staining and conventional plate counts

The viability of lactic acid bacteria (LAB) from commercial fermented milks was studied during storage at 4 °C. The enumeration of total viable bacteria was assessed using fluorescence microscopy. Plate counting on selective media was used to enumerate LAB. Using LIVE/DEAD® BacLight^TM viability staining, it was observed that bacterial counts decreased gradually after expiry dates, the number of viable bacteria remaining above 10⁶ bacteria g^?1 for all of the products. Viable cell counts estimated by plating onto selective media were lower than those obtained by direct microscopic counting. The viability of LAB contained in acid products decreased during their storage period at 4 °C. All products contain viable LAB ranging from 10⁸ to 10⁹ bacteria g^?1 and could be considered as probiotic, given that the recommended minimum number of probiotic bacteria in such food products is approximately 10⁷ bacteria mL^?1 product. The number of bifidobacteria in commercial fermented milks declared to contain bifidobacteria varied from 10⁴ to 10⁷ bacteria mL^?1. This study confirms the usefulness of fluorescent techniques for a rapid and accurate evaluation of bacterial viability in probiotic products.     

Extending the shelf-life and proximate composition stability of ready to eat foods in vacuum or modified atmosphere packaging

The stability of the proximate composition (moisture, proteins, lipids and ash) and the microbiological state of cooked ‘ready to eat’ foods in vacuum or modified atmosphere packaging were examined and compared with conventionally packaged (in air) foods. The study was carried out for 7 and 29 days, during which time the food products were stored at 3°C. Vacuum or modified atmosphere packaging were effective for prolonging the shelf-life of the studied products up to 29 days with minimal changes in the proximate composition. Aerobic mesophilic, psychrotrophic microrganisms, and yeasts and moulds increased with time regardless of packaging type but more rapidly under conventional packaging.     

Book review

Dr. Antonia J. Jones is a Senior Lecturer in Computing at Imperial College, London, working in the field of Neural networks and Adaptive Pattern Recognition.     

Evolution of biochemical and rheological characteristics and breadmaking quality during a multistage wheat sour dough process

Summary The evolution of some biochemical (acetic and lactic acid contents, fermentation quotient and changes in mono-, di-, and trisaccharides), rheological and fermentative characteristics (extensigram, maturogram and impulsogram) and bread quality (volume, density, texture, and degree of acidification) during a multistage wheat sour dough process have been investigated. Acetic acid contents of sour doughs (SD), bread doughs (BD) and breads (B) increased with the increase in number of processing stages. Lactic acid followed similar trends in SD, but in BD and B it reached maximum levels during the third stage. SD contained higher amounts of acids than BD and B. Dynamics of sugars followed patterns according to the fermentative activity and microflora evolution in the different steps. An improvement as the number of SD stages increased was observed in rheological and fermentative properties of BD, such as in oven spring. A positive effect on B characteristics (volume, density, texture, and acidity) was also observed. The last stage of the SD process led to the best final product, with noticable differences in relation to those occurring with a smaller number of stages.

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Entwicklung biochemischer und rheologischer Eigenschaften und des Backverhaltens während einer mehrstufigen Weizensauerteigführung

Zusammenfassung Es wurde die Entwicklung biochemischer Daten (Essigsäure- und Milchsäuregehalt, Gärungsquotient und Veränderungen an Mono-, Di- und Trisacchariden, rheologischer und Gäreigenschaften (Extensograph, Maturograph und Ofentrieb) und der Brotqualität (Volumen, Dichte, Textur und Säuregrad) während einer mehrstufigen Weizensauerteigführung untersucht. Die Essigsäuregehalte von Sauerteigen, Brotteigen und Broten stiegen mit der Zahl der Führungsstufen an. Beim Milchsäuregehalt ergaben sich ähnliche Tendenzen, jedoch beim Brotteig und Brot wurde das Maximum erst in der dritten Stufe erreicht. Veränderungen des Zuckergehaltes stimmten mit der Gäraktivität und der Mikrofloraentwicklung in den verschiedenen Stufen überein. Es ergab sich eine Verbesserung in den rheologischen und Gäreigenschaften von Brotteigen sowie im Ofentrieb, wenn die Zahl von Sauerteigstufen anstieg. Es wurde auch ein positiver Einfluß auf die Broteigenschaften (Volumen, Dichte und Säuregrad) beobachtet. Die letzte Stufe der Sauerteigführung ergab das beste Endprodukt mit deutlichen Unterschieden, wenn mit einer geringeren Zahl von Stufen hergestellt.

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Paper presented in part at the 7th World Congress of Food Science and Technology, Singapore (Singapore), September–October, 1987     

Well reservoir model identification using translation and scale invariant higher order networks

This paper describes the use of higher order neural networks to identify well reservoir response models from test data. Well reservoir response models are characterised by a family of parametrically related curves. Neural networks can in principle offer an interesting approach to the identification problem as data are often uncertain and incomplete. However, it turns out that the well reservoir model, viewed as a curve in two dimensions, is invariant with respect to translation and changes of scale of the axes. This poses severe problems for a standard backpropagation network using the two-dimensional plot as an input retina. This difficulty can be overcome by using a higher order network in which the output is forced to be invariant with respect to the required transformations of the retina. In this way, the potentially huge number of weights is significantly reduced using the invariance condition as a constraint which acts so as to divide the weights into equivalence classes within which they are equal. The resulting network can then be trained using standard techniques. We contrast this network approach with classical methods of model identification.     

Effect of processing methods on spinach: Proximate composition in fatty acids and soluble protein

The proximate composition and fatty acid content of spinach were determined in two processing stages. Crude protein and ash content were 2.89% and 1.96%, respectively. The total lipid content was 0-61%. The predominant fatty acids were palmitic (16:0), hexadecadienoic (16:2), hexadecenoic (16:1), stearic and hexadecatrienoic (18:0 and 16:3), oleic (18:1), linoleic (18:2) and linolenic (18:3). Little loss was observed as a result of processing. Soluble protein content showed losses of up to 87% during processing.