Membrane Packaging System to Permit Safe Hydration of Freeze-Dried Contents with Impure Water

We tested the feasibility of using polymer membranes for a self-hydrating packaging system to reconstitute freeze-dried foods using nonpurified water. Several commercial membranes were screened according to (1) hydration rate, (2) water permeability, (3) passage of microorganisms, (4) salt rejection, and (5) strength. The most promising membranes were used for developing and testing prototype packaging systems. A feasible self-contained rehydration system was a nylon-6 polyamide membrane that rehydrated the freeze-dried food within 30 min while passage of microorganisms was prevented. The temperature was 37°C, and the food contained 0.5g/5g of a low molecular weight solute (salt). Such self-contained membrane rehydration systems must be designed to accommodate expected environmental conditions such as temperature, relative humidity, and nature of the product.     

Quality and Nutritional Changes in Frozen Breaded Shrimp Stored in Wholesale and Retail Freezers

Chemical, microbiological, and sensory changes were monitored in breaded fantail shrimp held in upright and coffin style freezers at two retail markets and in a large warehouse freezer. Quality and nutritional changes in a test lot of shrimp were followed for 13 months. Significant sensory deterioration can be detected as early as 3 - 4 months after production when shrimp are stored in a retail freezer. Minimum retail freezer temperatures reached ≤-20°C between 1% and 36% of the monitored days and had daily temperature variations of 12 - 18°C. Storage at the wholesale level below -20°C with maximum daily temperature variations of 2 - 3°C proved to be an effective method to maintain the quality of frozen shrimp for at least 13 months of storage.     

CHARACTERISATION OF PATTERNS OF CHEWING BEHAVIOUR IN HUMAN SUBJECTS AND THEIR INFLUENCE ON TEXTURE PERCEPTION

Electromyography was used as a noninvasive and unobtrusive technique to characterise chewing patterns for a range of foods. Differences between subjects for a variety of aspects of chewing sequence are recorded for a range of foods (carrot, apple, roast pork, salami, biscuit and toast). Identifiable subgroups of subjects differing in chewing behaviour existed within the random sample of 52 dentate subjects. The five subgroups accounted for 52%, 21%, 11%, 10% and 6% of the sample population. Major discriminating factors between the behavioural groups lie in their chewing time and the muscle work rate during chewing. Sensory ratings for firmness and rubberiness of model foods differed significantly between the subjects exhibiting different chewing behaviours. Chewing behaviour may influence consumers' perceptions about the texture of a food.     

Storage Changes of Fresh and Pasteurized Blue Crab Meat in Different Types of Packaging

We investigated pasteurization and storage of blue crabmeat in steel cans, aluminum cans, plastic cans, nonbarrier pouches, and barrier pouches. Fresh meat was packed in copolymer polyethylene/polypro-pylene cups, Saran® over-wrapped or vacuum skin packaged polystyrene trays, and nonbarrier pouches. Meat pasteurized in plastic and aluminum cans had better sensory and microbiological quality and longer shelf life than meat packed in steel cans. Oxygen-barrier pouches had the lowest quality and shortest shelf life. Nonbarrier pouches had product with quality similar to meat in steel cans, but with an extended shelf life. No packaging materials improved the microbiological shelf life of freshly cooked meat. Vacuum skin packaging resulted in improved sensory qualities of freshly cooked and picked meat.     

Thermal Decomposition of Europium Hydroxide

The thermal decomposition of europium hydroxide in an air atmosphere was investigated by means of weight-loss measurements, infrared spectroscopy, X-ray diffraction analysis, and electron microscopy. These studies showed that EU(OH)° decomposed at temperatures between 225° and 300°C into EuOOH, which was stable up to about 425°C. Between 435° and 465°C this compound decomposed into cubic Eu₂O₃, which was stable until its inversion to the high-temperature monoclinic form. X-ray diffraction data were collected for Eu(OH)₃ and EuOOH and showed that the trihydroxide has a hexagonal crystal structure and the oxyhydroxide is possibly orthorhombic. The Eu(OH)₂, EuOOH, and cubic EunOa powders contained particles up to several microns in size consisting of agglomerates of crystallites in the size range 200 to 400 A. The single monoclinic Eu₂O₃ sample studied contained crystallites whose average size was greater than 2000 A.     

ENZYMATIC AND SOME BIOCHEMICAL CHANGES ASSOCIATED WITH THE PRODUCTION OF "KANTONG," A TRADITIONAL FERMENTED CONDIMENT IN NORTHERN GHANA

This paper reports on the activities of three major food enzymes (amylase, protease and lipase) during the traditional fermentation of Ceiba pentandra seeds into "kantong," a condiment used in Northern Ghana for soups. Samples were taken at periodic intervals during the fermentation, and enzyme activities and other parameters were determined. All enzyme activities increased steadily during fermentation, but leveled off when the fermentation was stopped at 48 h and the product dried. The increase in enzyme activities led to significant reductions in the levels of fiber and lipids, whereas protein and ash contents increased significantly ( P <  0.05). The fermentation produced significant increases in the concentration of all the amino acids. The process was acidic, as the pH dropped from 6.95 to 4.91. "Kantong," used in poor homes as substitute for meat or fish for flavoring soups, can serve as a nutritious condiment in the diet and its consumption should be encouraged.

PRACTICAL APPLICATIONS

"Kantong" is a traditional fermented condiment produced by the fermentation of the seeds of silk cotton (Ceiba pentandra). It is widely used in Northern Ghana as flavoring for soups and stews. However, no scientific studies about the fermentation process have been carried out. A scientific understanding of the fermentation process will enable a technological improvement on the process, either by the use of starter cultures or the addition of exogenous enzymes to the medium for the substrate conversion. The work also provided information on the nutritional value of the product, and thus its role in providing food security to the people who use it. The microbiological aspects of the fermentation are described under a different topic.     

A DIRECT SOLUTION TO THE BLOCK TRIDIAGONAL MATRIX INVERSION PROBLEM

A new theorem giving a direct solution for the inverse or a block tridiagonal matrix is proved. The algorithm is compared to that of Thomas and found to be less efficient in the general case, but more efficient in several practical special cases. In particular the algorithm is shown to be the general case of the various Marching Algorithms whose application to distributed systems is well known.     

Matrix synthesis of harmonic oscillator circuits †

A synthesis method is given for oscillators of the type that may be represented as a single two-port network with a transmission matrix [T]=[A, B;C, D] having its output fed directly back to its input, thereby imposing the condition:

A+D?Δ?1=0,

where ΔΞAD? BC. To obtain sustained oscillation at a single real frequency ω₀ this condition is interpolated at ω₀ by a polynomial equation in s. By identifying the two equations a set of functional values may be obtained for the [T] matrix elements. Four sots of basic circuit are developed in detail from the quadratic or cubic polynomial equation, with Δ = 0 or Δ≠0. Those having Δ = 0 arc well-known forms, but those with Δ =0 are novel.     

State-space approach to discrete-time,ℋ∞ control

State-space solutions to a discrete-time _?∞ problem are given. For a given number γ>0we give a characterization of all controllers such that the _{? ∞} norm of the closed-loop transfer function is less than γ The approach taken is based on the solution of two Riccati equations using the stable deflating subspace of a symplectic pencil. This ensures that no unnecessary assumptions on the ‘A’ matrix on the realization of the transfer function are needed. While the results are the direct analogues of those in the continuous time, the state-space derivation is considerably more difficult.