D. Hadziyev

Microstructure of Raw and Granulated Potatoes

Abstract Raw potatoes, var. Netted Gem (Russet Burbank) grown in Alberta, and those processed into dehydrated granules were examined by scanning electron microscopy. Photomicrographs were provided for periderm, cortex, vascular ring, inner and outer phloem, and pith zones. A fractured cross section through storage parenchyma cells revealed starch grains of various shapes and sizes. The cell walls, which had a furrowed or ribbed inner surface, were readily distinguished from the middle lamella. The isotropic arrangement of the cellulose network after enzymic removal of embedding pectin indicated that only a primary cell wall exists in parenchyma cells. Finally, changes in cells and their constituents were studied for the add-back granule processing steps of pre-cooking, cooking, mashing, conditioning-predrying, and fluidized bed drying. Microscopic observations were then related to some textural quality and chemical composition results.

Headspace Sampling Procedures for Onion (Allium cepa L.) Aroma Assessment

Abstract In order to study the effect of nutrition, irrigation, variety and dehydration on onion flavor strength, analytical procedures based on headspace sampling of volatiles were evaluated. A procedure using a porous polymer, Tenax–GC; to concentrate the headspace volatiles by trapping followed by gas chromatography with or without a liquid phase column was found to be most suitable. Reproducibility of the results required standardization of the sampling procedure. Of major importance were the extent of sample disintegration, incubation temperature, timing and the rehydration ratio of dehydrated samples. Quantitative data for the volatiles of fresh onion slices were also provided and compared with those dehydrated by a pilot–scale process.

Effects of Surfactants and Freezing and Thawing on Starch and Pectic Substances in the Production of Dehydrated Mashed Potatoes

Abstract The effects of surfactants on starch gel and on water soluble pectic substances formed during the production of potato granules were studied. In potato mash two kinds of surfactants — glycerol monostearate alone, and a mixture of glycerol- and propylene glycol-monosterates — were found to reduce the content of free “non-clathrated” starch. This decrease was followed spectrophotometrically by the blue color absorbance (Blue Value Index) due to the iodine affinity of free starch. The reduction of the Blue Value Index was linearly proportional to the amount of the surfactants added up to a certain level, beyond which further addition of the surfactants had no influence. When the mash was cooled to 5.5°C the presence of surfactant did not noticeably effect the Blue Value Index. However, freezing and thawing drastically reduced this Index regardless of the presence of any surfactant in the mash. The combination of a surfactant and freezing and thawing effected a greater reduction of the Index than either of the treatments alone. Similarly, potato granules processed by the freeze-thaw treatment without the addition of surfactant had a considerably higher Blue Value Index than those processed with the addition of the surfactant. In a model system using slow set pectin solutions and a surfactant, it was found that a mixture of glycerol- and propylene glycol-monostearates at 0.1%, and glycerol monostearate alone at 0.05%, reduced the viscosity of a 1% pectin solution to a minimum. Alternatively, excessive amounts of the surfactants in the solutions brought about an increase in the viscosity. This effect of surfactant on pectin, as well as that on free starch content, was used in the production of potato granules by the freeze-thaw technique and this resulted in granules superior to those processed by the conventional add-back procedure.

Tuber and Starch Characteristics of Alberta Grown Potatoes

Abstract Starches isolated from Netted Gem potatoes of three graded sizes grown commercially in Southern, Central and Northern Alberta were studied for physicochemical properties such as grain size distribution, mineral composition, amylose/amylopectin ratio, and swelling and solubilization patterns. In addition anatomical characteristics of the tubers were studied. Statistical analysis indicated the highly significant role of location of growth in influencing tuber and starch properties. Scanning electron micrographs were used to illustrate the behavior of starch grains during gelatinization.

Lipids in Raw and Granulated Potatoes

Abstract Data on lipids were provided for raw potatoes, var. “Netted Gem”, and for changes during a freeze-thaw process. Phospholipid was 52% of the total lipids of raw tuber, followed by glycolipid (20%), and sterol lipid (16%). The major glycolipids were digalactosyl and monogalactosyl di-glycerides, the latter being the most unsaturated tuber lipids. Sterols present were cholesterol, stigmasterol, and β-sitosterol, which was close to 80% of the total sterols. Triglycerides and other neutral lipids, including free fatty acids, were only 12% of the total lipids. Lipid losses in steam cooking, mashing, and dehydration steps were 14.7%, with the major portion being phospholipids. However, since the unsaturation ratio of most lipids in freshly processed freeze-thaw granules was still very high, off-flavor development during prolonged storing or shipping would not be surprising.

Essential Oils From Spices Grown in Alberta Dill seed oil, Anethum graveolens, L. (Umbelliferae)

Summary The common and Danish dill ( Anethum graveolens, L ) grown in Alberta was observed over three consecutive growing seasons for its horticultural performance and its oil quality. The overall horticultural performance of the plant, with irrigation applied, was rated as very good, although at harvest time the dill fruits were still unevenly matured. The seed oil yield varied from 1.2 to 1.8% on a dry weight basis. Its composition, analyzed by combined TL- and GL-chromatography and by mass spectral and infrared analyses, showed the presence of three major constituents, D(+)-carvone, D(+)-limonene and D- α -phellandrene, which made up close to 90% of the oil. The intermediate and minor constituents, a total of eight compounds, amounted to close to 8%, with slightly less than half being ascribed to a tetrahydrocoumarane derivative that was followed in abundance by dihydrocarvone, β -phellandrene and β -myrcene. The main differences in the two dills grown under identical conditions were a higher content of D(+)-carvone in common dill oil and a higher content of the cumarane derivative in Danish dill oil. For quality assessment and comparison, results are given for standard and prime grade dill oils imported and used by the domestic food industry.

Effect of Heat on Molecular Weight and Charge of Potato Sap Proteins

Abstract Potato sap proteins of several commercially grown Alberta cultivars were characterized by SDS–electrophoresis and isoelectric focusing on polyacrylamide gels. Native proteins were represented by major bands corresponding to 12, 17 and 38–40 × 103 daltons. Heat treatment brought about depolymerization of the 17 × 103 dalton band into polypeptide(s) close to 104 daltons, with simultaneous polymerization of the latter into dimers, trimers and tetramers. Isoelectric focusing of native proteins in pH 3–10 ampholyte revealed a total of 40–45 components. Some of them, among both acidic and basic proteins, were unique for a given cultivar. Heat treated proteins were characterized by the absence of several bands in the basic region and by increased mobilities of acidic proteins toward the anode. Scanning electron microscopy showed that in situ heat treatment brings about extensive denaturation of globular proteins but not of crystalline protein bodies.

Pyrazine Retention During Production of Dehydrated Potato Granules

Abstract The levels of natural pyrazines in granules from an add-back process and in potato flakes, and pyrazine retention during a freeze-thaw granule process were monitored. Alkylated pyrazines and 2-methoxy-3-ethylpyrazine were used in the retention study. When incorporated into moist mash, which was then subjected to dehydration steps, the losses of pyrazines were 65.7–85% in the pre-drying step, with additional losses of 14.3–18.3% in the granulation step, while final drying brought about a granule end-product in which the loss was 99.9%. The extent of pyrazine losses appeared to be dependent only on the amount of moisture removed. Qualitative and quantitative analyses were based on the application of differential pulse polarography instead of conventional gas liquid chromatography. Half-wave potentials of pyrazines in acetate buffer, pH 4.90, were reported, and an extraction procedure, which improved the detection limit of pyrazines to a level of 1 part per 10 9 , was developed.

Gamma Irradiation Effect on the Sulfhydryls Content of Skimmilk Powder

Abstract The effect of gamma-irradiation of skimmilk powder on the sulfur-containing constituents that may contribute to flavor defects when the powder is recombined with water, was investigated. Before irradiation no free –SH groups were detected in the laboratory prepared powders but they were present (18.5xa0mm/ lOOg) in the commercial high heat powder studied. After the application of irradiation doses of 0.4, 0.8, 1.2 and 1.6 Mrads the percentage increase in the –SH groups of the laboratory produced powder was 15.3 to 69.2 for free, 6.4 to 9.3 for masked and 6.4 to 29.3 for total sulfhydryl groups. The corresponding results for the commercial powder were 2 to 20 for free, 7.3 to 9.4 for masked and 12.8 to 32.3 for total –SH groups. The addition of ascorbic acid to the liquid skimmilk which after drying, amounted to 2.7 to 23.8xa0mm/100 of powder was reflected in a 2.4 to 16.5% decrease in total –SH groups when an irradiation dose of 0.4 Mrads was applied. Ascorbyl palmitate added under the same conditions and concentrations decreased the total –SH groups by 3.5 to 29.9%. Similar protection of the powder was obtained when the irradiation dose was 1.6 Mrads. The irradiation of skimmilk powder containing labelled 14 Ci-ascorbic acid revealed degradation products which could be recovered as carbonyls.

Effect of Cysteine on Volatile Development in Dehydrated Onions (Allium cepa L.)

Abstract The volatiles developed from dehydrated onion during rehydration with water or 1xa0g/ l cysteine solution were trapped on a porous polymer, Tenax-GC, and analyzed by an on-column entrainment gas chromatography procedure. Rehydration temperatures of 22 and 40°C, and four “sampling-trapping” times were investigated. Samples rehydrated with cysteine solution generally gave less total volatiles when the sampling-trapping period was 15, 30 and 60xa0min and more after 2 hours than water rehydrated samples. Propionaldehyde, 1-propanol and 1-propanethiol contents were always higher in samples rehydrated with water. The plausible reactions responsible for the observed effect of cysteine are discussed.