EXTENDING THE PROOF PLAN METHODOLOGY TO COMPUTER CONFIGURATION PROBLEMS

Can the technique of proof plans, developed originally for use in theorem proving, be successfully applied outside mathematics? We look at a problem associated with the configuration of large computer systems, namely that of checking orders drawn up by sales people on behalf of customers. Strategies exist for this task which may be explicitly encoded. We discuss the formation of plans for order checking and the factors involved in determining whether such plans can be guaranteed to succeed.     

CLASSIFICATION OF GREEN PEA PEROXIDASES BY PREPARATIVE ISOELECTRIC FOCUSING

Green pea peroxidase isoenzymes were partially purified, identified, and grouped by preparative isoelectric focusing in granulated gel (PEGG), using a modified cascade method. Isoenzyme patterns were detected utilizing a substrate-impregnated paper print technique. Direct application of crude extract on PEGG proved to be a valuable tool for partial purification of peroxidase isoenzymes. A substrate-impregnated paper print technique enabled the detection of isoenzyme patterns and may replace the time-consuming conventional peroxidase activity assay. Twelve isoenzymes (pIs ranging from 5.5–8.6), isolated on analytical thin-layer isoelectric focusing on polyacrylamide gel, were isoelectrically homogeneous.     

POTATO EXTRACTIVES: EFFECT ON FIRMNESS OF PECTIN JELLIES AND VISCOSITY QF POTATO STARCH PASTES

SUMMARY— Pectin jellies and potato starch pastes were prepared with aqueous extracts of potato tissue. All jellies containing potato extractives were weaker than distilled water control jellies. Jellies containing extractives from bud tissue were weaker than those containing extractives from stem tissue. Extractives from tubers stored continuously at 38°F weakened the jellies to a greater extent than those from tubers stored at 38°F and conditioned for 1 wk. Jellies containing extractives from boiled tissue were weaker than those prepared with extractives from blanched or steamed tissue. The most viscous pastes were those made with distilled water. In every case, viscosity of pastes containing extractives from raw tissue was less than half that of distilled water pastes. When extractives from blanched, steamed or boiled tissue were used, the viscosity decreased still further. The rigidity of jellies and the viscosity of pastes prepared with deionized extracts were similar to those of jellies and pastes prepared with distilled water. The data suggest that extractives leached from potato tissue increase sloughing of potato tissue during cooking by weakening the pectic materials in the intercellular cement rather than by enhancing the swelling of starch in the cells.     

OPTIMIZATION OF PROCESSING CONDITIONS FOR KUNUN-ZAKI, A SPONTANEOUSLY FERMENTED CEREAL-BASED BEVERAGE

Kunun-zaki production was monitored at six sites for the evaluation of microbiological quality, potential hazards and identification of critical control points, with the aim of setting critical limits for process optimization. Samples were collected at various stages of production and examined microbiologically for potential pathogens, before and after optimization. Critical limits were established for the critical control points identified, and two producers were selected for testing the effectiveness of corrective actions in an optimized process. Samples of kunun-zaki recorded total viable counts ranging from 3.84 to 4.80 log₁₀ cfu/mL. Bacillus cereus, salmonellae and staphylococci were isolated in samples at 0.00–0.01, 0.57–0.76 and 1.70–2.04 log₁₀ cfu/mL, respectively. The application of corrective measures, such as hand-washing practices, washing of processing areas and utensils, hygienic handling of materials during processing and pasteurization of final product proved effective in significantly reducing (up to 80%) the microbiological hazards associated with kunun-zaki.

PRACTICAL APPLICATIONS

The findings of this study have shown that with minimum hygienic food-handling practices, the incidence of food-borne pathogens in local foods and drinks can be reduced if not eliminated, even at household level of production. The work itself is practicable at the current level of kunun-zaki production and holds application for pilot-scale processing. The results can be used to set national standards for this and other related drinks. It also provides baseline data for standardization of kunun-zaki production, the focus of ongoing research by the authors.     

The effect of some manufacturing conditions on the development of flavour in Cheddar cheese

Organoleptic assessments by the NIRD panel of Cheddar cheeses made with Streptococcus cremoris NCDO 924 or 1986, either in enclosed vats excluding nonstarter flora or in open vats, showed that high viable starter populations in curd did not give stronger-flavoured cheese, but led to the development of bitterness. Cheeses made in open vats developed typical flavour more rapidly than those made in enclosed vats. Maturation temperature was the most important factor in determining the flavour intensity; cheese ripened at 13d?C for six months had stronger flavour than corresponding ones ripened at 6d?C for nine months, irrespective of the starter or vat used.     

A COMPARISON OF THE VISCOELASTIC PROPERTIES OF CONVENTIONAL AND MAILLARD PROTEIN GELS

The properties of gels prepared by heating solutions of bovine serum albumin (BSA) for 30 min at 121C in the presence and absence of glucono-delta-lactone (GDL gels) and xylose (Maillard gels) were compared. During formation the pH of the Maillard and GDL gels decreased to 4.9 whereas the pH of the gels formed in the absence of GDL or xylose remained near neutral. Maillard gels show much less syneresis compared with the GDL gels and contained nondisulphide covalent crosslinks as evidenced by very low protein solubilities in mixtures of sodium dodecyl sulphate and β-mercaptoethanol. Both the GDL and Maillard gels could be formed at much lower protein concentrations than the neutral conventional gels. The stress relaxation of the gels in compression was measured and the response analyzed using Peleg's equation. The parameters in this equation were not strongly dependent on protein concentration or degree of deformation. The neutral pH gels were far more elastic than the low pH gels, but despite the difference in crosslinking mechanisms the viscoelastic behaviour of the Maillard and GDL gels was similar. However, the break strength and asymptotic residual modulus of the Maillard gels were higher. It is suggested that the stress relaxation occurs in weaker, noncovalently linked regions of the gel, whereas the nondisulphide covalent crosslinks in the Maillard gels reinforce strong regions already containing disulphide linkages.     

Effect of Storage and Cooking on Qualities of Loin and Top-Wound Steaks

SUMMARY— Boneless, trimmed steaks (U. S. Good) from the longissimns dorsi muscle (loin) and semimembranosus muscle (top-round) and conventionally cut loin steaks were removed 8 days post-mortem, quick-frozen and stored at −18°C to −23°C for three storage periods, 0, 6, and 9 months. Steaks were sampled at each storage period and cooked to an internal temperature of 70°C in a microwave oven and electric range. Quality was evaluated by chemical tests, sensory evaluations and cooking loss data.
Storage up to 6 months had little effect on loin steaks with the exception of TBA values, but significant changes occurred between 6 and 9 months. Loin steaks had increased cooking losses and decreased juiciness scores, percent moisture, and juice content. TBA values increased with each storage period. Top-round steaks at the 9-month period showed a decrease in collagen content and juiciness and flavor scores, and an increase in TBA values. Storage up to 9 months did not influence tenderness in either muscle.
Conventionally broiled loin steaks had higher palatability scores, cooking losses, percent moisture, percent total proteins, and lower percent total lipids than did microwave cooked loin steaks. Electronically cooked top-round steaks had higher total cooking losses and percent total proteins and lower collagen values than did conventionally roasted top-round steaks.
The qualities of boneless loin steaks did not differ significantly from those of conventionally cut loin steaks when compared at each storage period.     

EFFECTS OF DRY AND MOIST HEAT ON SELECTED HISTOLOGICAL CHARACTERISTICS OF BEEF SEMIMEMBRANOSUS MUSCLE

ABSTRACT— Samples of raw and heat-treated beef semimembranosus muscle were examined histologically to determine how deep-fat frying, oven roasting, oven braising and pressure braising to 70°C affected histological characteristics of the muscle. A panel of three persons used an ocular micrometer to measure muscle fiber width, observed color and type of connective tissue and distribution of fat and estimated quantity of connective tissue of 475 histological sections. Differences among heat treatments in muscle fiber width and relative proportion of straight and wavy connective tissue were not significant. However, there was a significantly (P<0.05) larger quantity of granular tissue in deep-fat fried, pressure braised, and oven braised samples than in oven roasted samples. Intact fat cell walls were observed in both raw and heated samples.     

The use of carotenoid preparations for colouring Cheddar cheese

Annatto extracts prepared from Bixa orellana have traditionally been used for enhancing the colour of Cheddar cheese made in winter in Southern England or throughout the year in Scotland, and also to produce the deep red colour of certain varieties of cheese, e. g. Leicester. Double Gloucester, Red Cheddar and Cheshire. However some of the colour passes into the whey and this can lower the commercial value of powder made from the whey.
A series of Cheddar cheeses was made to compare carotenoid preparations based on β-carotene as the colouring agent with the traditional carotenoid colourant norbixin present in annatto solutions. The β-carotene preparations were found to enhance the colour of Cheddar cheese, made in Southern England from winter milk, to that of Cheddar cheese made from summer milk, or to the colour of New Zealand Cheddar, with only traces of the colourant passing into the whey.
For colouring milk to make Leicester, Double Gloucester, Red Cheddar or Cheshire cheeses, β-carotene preparations are too yellow and would need the addition of carotenoids with a more reddish colour. However, even at the highest level used, little of the β-carotene passed into the whey.