Electrophoretic and Chromatographic Changes in Egg Yolk Proteins Due to Heat

Polyacrylamide gel electrophoresis and diethylaminoethyl-cellulose ion-exchange chromatography were used to observe changes in egg yolk products which were heat treated at 3°C intervals from 54 to 84°C for 3.5 min. The USDA pasteurization temperatures of 61.0, 63.3°C for plain, 10% sugared, and 10% salted egg yolk, respectively, had little effect on their electrophoretograms. Only the γ-livetins in plain yolk were slightly affected. Higher temperatures progressively altered these proteins until they disappeared from the electrophoretograms from plain yolk ca 73°, sugared yolk ca 76°, and salted yolk ca 79°C. The lipovitellin fraction and phosvitins were similarly affected by increasing temperatures. Sugar and salt at 10% levels had a protective effect against heat, allowing respectively ca 3° and 6°C higher temperatures before heat damage occurred. The chromatograms from plain and sugared yolk were little affected by pasteurization. However, major changes were noted between unheated and pasteurized (63.3°C) salted yolk. Patterns for salted yolk, pasteurized at 63.3 and 68.0°C were similar, which further indicated that this product can be pasteurized at 68.0°C without significant damage.     

HEAP BIOOXIDATION OF REFRACTORY GOLD ORES: CURRENT STATE OF THE ART

Heap leaching of low-grade refractory sulfidic gold ores has generated much interest during the last decade. Attention has focused primarily on improving gold extraction, with less concern about understanding how the multiple phenomena that are involved determine the overall sulfide oxidation rate. Varying the conventional operating parameters (flow rate, particle size, height) has had little impact on sulfide oxidation beyond the average of 10–15%/month. Variable aeration flow, adequate supply of carbon dioxide, finetuning of temperatures, well-defined particle kinetics, and a careful balance between coarse and fine ore particles may hold the key to successful commercial practice.     

SHORT COMMUNICATION: EVOLUTION OF BACTERIAL COMMUNITY IN A PYRITIC REFRACTORY GOLD ORE COLUMN LEACHING ENVIRONMENT

This short communication highlights important biological features of a pyritic refractory gold ore heap-leaching environment. Acidithiobacillus ferrooxidans and Leptospirillum ferrooxidans were to be two of only three bacterial species detected on the ore surfaces at ambient temperature. Sulfobacillus was not originally introduced in the inoculum, but was later detected in the column. Only organisms of the Leptospirillum genus were present in the ferric sulfate leaching solution. Ignoring that the ore hosted approximately 500 times more microorganisms than the solution can greatly underestimate the oxidizing potential. One or more of these microorganisms oxidized ferrous ions, leading to a rise in the solution potential. They also oxidized elemental sulfur, resulting in a higher sulfate yield than measured in sterile medium.     

Protein and Starch Digestibility and Flatulence Potential of Germinated Cowpeas (Vigna unguiculata)

In vivo and in vitro methods with experimental rats and commercial digestive enzymes, respectively, were used in assessing the protein and starch digestibility and flatulence potential of germinated cow-peas. Germination (24 hr at 25° or 30°C) reduced the flatulence potential of seeds (52 to 77%). In vivo digestibility of starch and protein was also significantly increase by germination. Germination did not affect in vitro protein digestibility, but reduced in vitro digestibility of freeze-dried and 70°C-dried starch. Cooking in boiling water significantly increased in vitro protein and starch digestibility of both ungerminated and germinated seed.     

FERMENTED COWPEA FLOUR: PRODUCTION AND CHARACTERIZATION OF SELECTED PHYSICO-CHEMICAL PROPERTIES

A simplified solid-substrate fermentation and milling process for preparing flour from nondecorticated cowpeas (cv. White Acre) was developed. Yield of fermented flours compared to starting substrate was about 73%. Total solids loss (ca. 21–23%) was due to soaking (6%), boiling (11%), fermentation (2–4%) and grinding (2%). Moisture loss during drying was approximately 5%. The pH of fermented flours ranged from 6.4 to 6.9. Fermented flours had less packed density but greater unpacked density than the control flour. About 41–44% of flour particles passed through a 0.297-mm sieve; 65–72% of these particles were in the exclusion range of 0.037–0.074 mm. An increase in color saturation of fermented flours was due mainly to increased b* (yellowness) values. Fermented flours contained about 28% protein, 1.8–2.0% fat, 4.9–6.2% moisture, 2.7% ash, and 61–63% total carbohydrate.     

Subject: Dairy technology - influences and constraints: The government view

The constraints on the dairy industry which are the concern of government are, from within the UK, the milk marketing system with its maximum milk prices and, from without, the limitations set by the EEC. The attempts of the EEC through the Common Agricultural Policy to control milk supplies by various financial schemes are of great importance to the industry. In particular, a restriction on support prices seems to be necessary to bring milk production more into line with demand.     

Induction cooking unit using a gate turn-off thyristor

This paper deals with the design and construction of a 500W 60kHz induction cooking power supply. The novel aspect of the unit is its use of a gate turn-off thyristor (GTO) in a resonant circuit topology, i.e. a Class E circuit.     

Hard-to-Cook Defect in Cowpeas: Storage-Induced and Treatment-Induced Development

Cowpea seeds with a range of hard-to-cook (HTC) levels induced by storage at various temperatures/relative humidities/times were subjected to heat incubation in water and/or soaking in CaCl_2. For control seeds, the hardening effect of Ca soaking was greatly increased by incubation at 60-85°C before soaking, but not after. For aged seeds, Ca soaking alone evoked a great increase in hardness whereas incubation slightly enhanced hardening. Trivalent cations induced HTC less effectively than divalent cations; univalent ions suppressed HTC. EDTA soaking completely reversed while EGTA partially reversed HTC state of aged seeds. HTC state in cowpeas apparently develops via two stages: an increase in cation-uptake capacity within cotyledons induced by moderate heat or adverse storage, followed by divalent cation binding.