Kenneth Eskins

Stable starch—lipid compositions prepared by steam jet cooking

Preparation of starch-lipid compositions by a steam jet cooking process for use as fat replacers and stabilizers in foods is described. The process involves using high temp. (140°C) steam pressurized at 40 psig, and turbulence within the cooker to uniformly disperse the lipid component within the starch-water matrix as small droplets (approx. 10-50 μm). The cooked dispersion was then cooled and viscosity measurements taken with a Brookfield viscometer. Viscosities varied with type of lipid (soybean, olive, rapeseed, butter and paraffin oils) and starch (corn, waxy corn, wheat and potato starches) used in the formulation, and ratio of starch to lipid. Cooked dispersions became viscous when cooled and formed soft gels at high solids concn., when reheated they became fluid and pourable, similar to semi-solid fat or shortenings. SEM showed that the lipid was uniformly dispersed within the starch-water phase as droplets; these droplets did not coalesce or separate even after drying. Dispersions could be drum-dried yielding a coarse flaked product which could be ground or milled into a free-flowing powder with a final moisture content of 5%.

Ultrastructural studies on microencapsulated oil droplets in aqueous gels and dried films of a new starch-oil composite☆

Abstract Combination of starch, water, and oil by a process utilizing an excess-steam jet cooker produces a new class of stable, oil-in-water dispersions. Examination of aqueous gels by light microscopy (LM) and transmission electron microscopy (TEM) and of dried thin films by scanning electron microscopy (SEM) shows that the oil is microencapsulated in the starch water matrix or in the dried starch matrix as droplets that are typically 1–10 μm in diameter. The size and distribution of oil droplets in cornstarch-soybean oil composites are determined by a number of factors, such as oil:starch ratio, the number of times the formulation is passed through the steam jet cooker during preparation, and the steam pressure used during cooking. Oil droplet size can be reduced by addition of protein or starch-oil composites from a previous cook to the formulation prior to cooking. Oil droplet distribution in these composites is observable not only in scanning electron micrographs of fracture surfaces, but also by light microscopy and by transmission electron microscopy of aqueous gels. Micrographs suggest the presence of a boundary layer surrounding the oil droplets which prevents them from coalescing.

Light Quality During Early Seedling Development Influences the Morphology and Bitter Taste Intensity of Mature Lettuce. (Lactuca sativa) Leaves

Summary The genetic constitution of a vegetable crop species such as lettuce. ( Lactuca sativa ) is an important determinant of characteristics such as leaf size, shape, texture, color, and taste. Whereas introduction of improved traits by breeding or genetic engineering is possible, an alternative approach involves modification of the mature phenotype by manipulation of the early growth environment. To explore this phenomenon, lettuce was grown under specific light quality treatments. (red, red + far-red, blue, and white light), both continuously and with color switching at various intervals. Leaves grown in continuous light quality showed characteristic differences in leaf area, shape, dry weight, and bitter taste intensity as determined by an analytical sensory panel. However, red light supplied for the first 7 d of growth conditioned weak bitterness intensity whether or not plants were switched to white light for 18 or 26 d. Leaf area and dry weight were determined by the first 7 d in red or blue light whether or not plants were switched to the opposite color light for 9 or 35 d. These observations demonstrate that persistent photomorphogenic switching of leaf development can take place before leaf emergence, and that light quality signals received in the early growth environment can have a latent effect on subsequent plant development.

Effects of red and blue light on the composition and morphology of maize kernels grown in vitro

Growth and development of plants are known to be affected by exposure to red and blue light. Mechanisms by which light quality influences gene expression in maize (Zea mays L.) embryos have not been explored. Maize kernels can be cultured in vitro allowing experimental manipulation of environmental factors during seed development. We used the in vitro kernel culture system to investigate the response of developing maize seeds, which normally develop without exposure to light, to controlled light quality. Kernels grown under red light accumulated more dry weight than those grown in darkness, whereas kernels grown under blue light accumulated less. Reciprocal color shift experiments showed that light quality during the first week in culture had more influence on kernel weight than during the subsequent three weeks in culture. Soluble sugars were higher in both light treatments than in darkness. Blue-grown kernels had higher amino acid and lower lipid levels than red-or dark-grown kernels. Embryo morphology was markedly affected by red light, under which the upper shoot axis was longer than under blue light or in darkness. Embryo morphology was influenced by light quality during the later stages of development rather than the first week. We suggest, based on these results, that gene expression in the embryo and endosperm of developing maize seeds is sensitive to light quality, and the mechanism and time dependence of this effect warrant further study. In vitro maize kernel culture affords a convenient system for such light quality experiments.

Blue and red-light irradiance switching of nuclear- and chloroplast-encoded gene expression in Arabidopsis and Sorghum

Abstract We have previously shown in maize chloroplasts an interaction between light quality and irradiance levels in control of the expression of genes associated with photosystem II, LHCP2 and psbA. Blue light decreased LHCP2 and increased psbA mRNA expression compared with red light of equal irradiance. Differences were irradiance related. Our present work examines irradiance and quality light regulation of LHCP2, psbA, rbcS, PEPCO and PPDK gene expression in two different species, Arabidopsis (C3) and Sorghum (C4) at different stages of development and shows that the blue light suppression of LHCP2 and enhancement of psbA gene expression also operates at 50 and 130 μmol m−2 s−1 total irradiance. It also shows that light quality effects on LHCP2 gene expression are dependent on the stage of development but those on psbA are not. Sequential light quality experiments indicate that chloroplast gene expression is plastic and responsive to the immediate environment. Switching effects of blue in red light during development in light mixtures with a constant irradiance (50 μmol m−2 s−1) are blue light irradiance regulated.