SACCHAROMETER CORRECTIONS AT LOW TEMPERATURES

Certain Tables for the correction of the readings of brewery saccharometers at temperatures below 10°C. have been found to contain errors. New values have been determined and these have been used to establish improved Tables.     

TRACE HYDROGENATION OF BUTTEROIL AT LOW TEMPERATURES

SUMMARY— The present investigation describes a process of selective trace hydrogenation of butteroil at low temperatures using palladium catalyst. Butteroil was selectively trace hydrogenated at low temperatures, in some instances in a semisolid state. The hydrogenated product had a remarkable flavor stability and without appreciable increase in trans-isomers and melting point. The hydrogenated butteroil also retained most of its desirable flavor and color.     

FLOW BEHAVIOR OF CLARIFIED ORANGE JUICE AT LOW TEMPERATURES

This paper presents a study of the rheological behavior of clarified and depectinated orange juices, with different soluble solid contents, at temperatures just above their freezing point. The rheological behavior of depectinated and clarified orange juice was determined for a wide range of soluble solid contents (10–65.8° Brix) and temperatures ( − 15 to 30C). The results indicated that the samples behave like a Newtonian fluid. The effect of temperature on the juice can be described with an Arrhenius-type equation. It was found that the activation energy for viscous flow was in the range of 9.4 to 59 kJ/mol, depending on the concentration. The effect of the soluble solid content can be described by an exponential-type equation. Finally, an equation in which dynamic viscosity depends on temperature and soluble solids content gives the following expression: η =  1  ×  10 ^{- 15} exp(0.12C  +  9021/T), where T in Kelvin, C in °Brix, and viscosity in mPa·s.

PRACTICAL APPLICATIONS

It is necessary to know the relationship between viscosity with temperature and concentration, since knowledge of these parameters is of vital importance in the manipulation, calculation and design of all those unit operations during the process, mainly those based on heat and quantum transfer.     

MICROFLORA CHANGES IN MISTED AND NONMISTED BROCCOLI AT REFRIGERATED STORAGE TEMPERATURES

Plate counts of three groups of microorganisms [aerobic plate count (APC), coliforms (C), and yeast and mold (Y/M)] were determined in misted (M), nonmisted in the same cold room (SNM), and nonmisted in a different cold room (DNM) broccoli stored at 4 ± 1C for five days. Relative humidity of the cold rooms, moisture content of the broccoli, and microbial quality of the misting water were also determined. Two-way ANOVA indicated significant differences (p ≤ 0.05) between M, SNM and DNM treatments. Misting was found to minimize the increase in plate counts of the three microorganism groups monitored. Higher relative humidity in the misted samples compared with the nonmisted samples, the washing effect of the misting water and possible residual chlorine effects due to the use of chlorinated tap water may explain the reduced viable counts observed in the misted samples.     

QUALITY CHANGES IN JICAMA ROOTS STORED AT CHILLING AND NONCHILLING TEMPERATURES

Mature jicama roots (Pachyrhizus erosus (L.) Urban cv. Agua Dulce) were stored at 5, 10, 13 and 20C for 1, 2 or 3 weeks and then transferred to ambient conditions (18–23C) for 1 week. Storage of roots at 5C and 10C for 2 weeks resulted in chill-induced decay and loss of intact root firmness. Increased rates of water loss after storage was another indicator of chilling injury; poststorage water loss rates after storage at 5C and 10C were double the rates of roots stored at 13C and 20C. With storage for 2 weeks, the pulp of roots stored at 10C showed brown discolored areas and this was best represented by decreasing L* values. The grey, translucent aspect of the pulp of roots stored at 5C resulted in L* values intermediate between those at 10C and 13C. Force to penetrate the pulp with a 5 mm probe decreased at 10C, but increased at 5C. The distance to rupture point increased at 5C and 10C, indicating loss of crispness. Jicama roots stored at 13C and 20C maintained good external visual quality and a white crisp pulp.     

BRUISING AND ENERGY DISSIPATION IN APPLES

A strong correlation was obtained between bruise volume and energy absorbed for both impact and slow compression of Granny Smith apples. Apple tissue was more easily bruised by slow compression than by impact. For the same amount of energy, bruise volumes were approximately 40% higher under slow compression. There was no correlation between the stiffness (force/deflection) of apple flesh and bruise volume. It is unlikely that the theories of failure based on the theory of elasticity will prove useful in predicting the extent of bruising. The application of elastic theory to bruise initiation was not studied in this paper. A simple model was formulated to explain the behaviour of apples under compression. Apple tissue was likened to an orderly arrangement of liquid-filled, spherical cells bounded by viscoelastic membranes with air-filled interstitials. It is postulated that on initial compression the cells are deformed into ellipsoids under a stress distribution similar to that found in an elastic sphere. Further compression would then result in cell wall fracture, i.e., cell bursting in regions of high shearing stress. Distortion and bursting of cells explains the energy dissipative mechanism. The work showed that energy absorbed during compression is a good predictor of bruising and is, thus, a useful parameter in evaluating handling and packing systems.     

COLOR CHANGES IN BANANAS AND PLANTAINS DURING STORAGE

Two cultivars, namely Cavendish bananas (Musa AAA Group) and plantains (Musa AAB Group) were used to study the changes in their peel color during storage at various temperatures. Gas-treated and nontreated fruits, and the L* a* b* system were used. The temperature effect on the color parameters was mainly through the interaction with the gas treatment, variety and storage time; however, redness (a*) for gas-treated bananas was expressed as a *=−20.1 + 0.14TD, (T= temperature, D = day). Similarly, a*=−27.5 + 55 (TD)^1/2− 0.2 T D, predicted the degreening process in gassed plantains. The gas-treatment, storage time and variety all had a significant effect (p<0.01) on the L*a*b* parameters. Plantains lost the greenness during storage faster than bananas.     

DIPHENYLAMINE RESIDUES IN APPLES AND APPLE CIDER

Diphenylamine (DPA) is an antioxidant which is widely used on apples for scald control during fruit storage. Since appreciable residues of DPA remain on apples when sold, it was of interest to study the extent of possible transfer of the compound to cider. Cider was expressed from five cultivars ofDPA-treated apples following their storage and the original fruit, the pomace and cider was analyzed for DPA residues. Only traces of the compound were found in cider with virtually all of the DPA found concentrated in the pomace. The toxicologic significance of the results are discussed.     

POST-MORTEM ISOMETRIC TENSION CHANGES AND SHORTENING IN TURKEY MUSCLE STRIPS HELD AT VARIOUS TEMPERATURES

SUMMARY: A study of the physical changes associated with rigor mortis in breast muscle was undertaken to assess the factors that may influence ultimate tenderness. Isometric tension changes and shortening were measured at temperatures 2–37°C. These changes were measured while holding the muscle strips in a phosphate buffer, pH 7.2. Isometric tension was measured by transducers and recorded on a physiograph. A pattern of tension development and gradual relaxation has been demonstrated to occur post-mortem in strips of turkey breast muscle held isometrically. The time to maximum tension development occurs in 3.85 ± 0.19 hr and is not linearly related ( P <.05) to temperature. The amount of maximum tension developed averaged 25 g/cm² and was significantly ( P < .05) related to temperature. Relaxation to about 50% of maximum occurs in 18 hr. The amount of shortening that occurs post-mortem is linearly related ( P < .01) to temperature. No "cold shortening" of turkey breast muscle was evident.     

FUNCTIONALITY IN BREADMAKING OF YEAST PROTEIN DRIED AT TWO TEMPERATURES

Yeast was spray dried at two temperatures (75°C and 124°C) and incorporated into a dough and bread system to measure functionality. The system dried at the higher temperature exhibited much better functional properties but was still not as good as milk solids. A cell wall-free extract of each of the dried yeasts was tested and showed much poorer characteristics than whole cells. This shows that cell wall removal is not needed for SCP manufacture.     

DYNAMIC AND STEADY-STATE RHEOLOGY OF AUSTRALIAN HONEYS AT SUBZERO TEMPERATURES

The rheology of 10 Australian honeys was investigated at temperatures ?15C to 0C by a strain‐controlled rheometer. The honeys exhibited Newtonian behavior irrespective of the temperature, and follow the Cox–Merz rule. G″/G′ and ω are quadratically related, and the crossover frequencies for liquid to solid transformation and relaxation times were obtained. The composition of the honeys correlates well (r² > 0.83) with the viscosity, and with 247 data sets (Australian and Greek honeys), the following equation was obtained: The viscosity of the honeys showed a strong dependence on temperature, and four models were examined to describe this. The models gave good fits (r ² > 0.95), but better fits were obtained for the WLF model using T_g of the honeys and µ_g= 10¹¹ Pa.s. The WLF model with its “universal values” poorly predicted the viscosity, and the implications of the measured rheological behaviors of the honeys in their processing and handling are discussed.     

SURVIVAL OF VIBRIO VULNIFICUS AT REDUCED TEMPERATURES AND ELEVATED NUTRIENT

Studies were conducted on the survival of the human bacterial pathogen, Vibrio vulnificus, in heart infusion broth held at 5, 10 and 15°C. Culturability was monitored by plate counts on heart infusion agar, and viability by examination of electron transport activity. Whereas V. vulnificus demonstrated growth at 15°C, a rapid loss of culturability for cells held at the lower temperatures was observed. At all temperatures, however, a significant portion of the population was found to remain viable over the 28 day study period. The ability of V. vulnificus cells to metabolize exogenously supplied nutrient at reduced temperatures was also examined as an indicator of viability. Cells were able to rapidly take up and respire mixed amino acids at 9 and 13°C, whereas cells incubated at 2°C showed relatively little metabolism of the labeled substrates. Like the growth and viability study, the radiotracer study indicates survival of V. vulnificus at reduced temperatures, although with reduced rates of activity. The possible implications of these findings for the transport and storage of shellfish is discussed.     

CHARACTERISTICS OF MINCED BEEF STORED AT CHILLED AND ABUSE TEMPERATURES

Fresh minced beef samples were collected from retail food stores in the Eastern United States and stored for various periods at 4 and 25C. Evaluations included psychrotophic counts, microbial taxonomy, pH, total volatile nitrogen, malonaldehyde (TBARS), color and off odor. Minimal discoloration was observed through 5 days of storage at 4C; whereas, minced beef stored at 25C sustained major discoloration prior to storage for 12 h. After five days of storage at 4C, 11.6% of the samples exhibited an off odor compared to 29.8% after storage for 12 h at 25C. Psychrotrophic counts of less than 10⁵/g were attained during storage at 4C for 5 days; whereas, samples stored at 25C exceeded this level after 12 h. Chemical indices suggested similar product deterioration. These observations suggested that fresh minced and aerobically packaged in a 4C environment will attain acceptable color without off odor development through 5 days of storage.