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Green peas were submitted to osmotic pretreatments in carbohydrate-salt syrups to evaluate the effect of alternative agents on quality and assess the stabilization accomplished during subsequent storage in a wide temperature range-down to −24°C, including the −3 to −12°C detrimental zone. Green color and L-ascorbic acid loss were kinetically studied, and their temperature dependence was modeled by Arrhenius and Will-iams-Landel-Ferry equations. Dehydrofrozen samples exhibited significantly improved stability, with the rate of L-ascorbic acid loss, being reduced by as much as 3-fold for peas osmotically pretreated with oligofructose, trehalose, and maltitol systems. The cryostabilization results are discussed in relation to glass transition behavior of the modified osmodehydrofrozen food matrix.

In a case study on green peas, nonuniformity in microbial lethality and nonuniformity in quality retention (color) in retort processing was investigated by combining nonuniformity in the product (heat penetration data) and nonuniformity in the retort (heat distribution data) through simulations. The fractional conversion model was applied to model the color degradation of peas. The temperature dependence of color degradation decimal reduction times could be described by TDT (Thermal Death Time) equations with a z-value of 47.5 ± 5.9 °C. Heat penetration trials were conducted on peas in brine to determine the variability in heating parameters. A theoretical optimization procedure was carried out, and an experimental verification of the calculated results was conducted.

The applicability of Time Temperature Integrators (TTI) for frozen chain management was assessed. Shelf life kinetics indices of frozen green peas and white mushrooms and response kinetics of suitable enzymatic TTI were used to confirm the monitoring effectiveness of TTI, in a controlled field test with 200 products. Comparison to actual measurements of quality indices showed that TTI response provides a reliable indication of the relative quality status of the products. The potential of Least Shelf-Life First Out (LSFO) system, a TTI based management system for frozen product distribution and stock rotation, was demonstrated by Monte Carlo technique that showed consistent, acceptable quality and minimization of rejected products at the consumer end.

Kinetics of lipoxygenase (LOX) inactivation in green peas (Pisum sativum) by temperature and/or pressure was studied at different levels of food complexity, namely in green pea juice and in intact vegetables (in situ study). Pea LOX in both matrices was irreversibly inactivated either by thermal or by combined pressure-temperature treatment, and the inactivation followed a first-order reaction. Pressure levels below 200 MPa retarded thermal inactivation of LOX at temperatures above 60°C. Moreaver, above 60°C, enzyme activation under pressure occured prior to inactivation. At elevated pressure, LOX inactivation rate could be accelerated by a temperature increase above 10°C as well as by a tempereature decrease below 10°C. The pressure-temperature dependence of the LOX inactivation rate constants both in green pea juice and in intact green peas was described successfully using the same mathematical model. On the basis of this mathematical model, an iso-rate contour diagram for LOX inactivation in green pea juice and in intact green peas was constructed. La cinetique d'inactivation de la lipoxygenase de petit-pois par un traitement thermique a haute pression est etudiee dans le jus de petit pois ou dans le petit pois entier. L'enzyme est inactivee de facon irreversible dans les 2 matrices apres le traitement thermique simple ou compine aux hautes pressions. La reaction est d'ordre 1. Le phenomene est decrit avec un modele mathematique qui peut egalement s'appliquer a d'autres legumes.

Bioavailability of iron from green peas, spinach, bran cereal and cornmeal was evaluated by hemoglobin regeneration efficiency in the anemic rat. By analysis these respective food items contained 85, 163, 55 and 35 mg of iron per kg of dry weight. Iron from ferrous sulfate, peas, spinach, bran cereal and cornmeal was converted to hemoglobin iron with respective efficiencies of 67, 64, 34, 53 and 39 percent. Based on these bioavailabilities, peas, spinach, bran cereal, and cornmeal provide 14, 19, 12, and 3 mg of available iron per 1000 kcal. Plant foods can make significant contribu tions of available iron in the diet.

The effects of freezing (still-air, air-blast, and Freon immersion freezing) and frozen storage (−5°, −10° and −15°C for 0 to 48 wk) on texture of cooked frozen peas were examined. Peas frozen by a Freon-12 immersion method with no appreciable damage to cell structure had firmer and more chewy sensory textural quality compared to those peas frozen by a slower freezing method. Sensory tenderness decreased initially and then increased with storage time to the maximum storage times of 6 wk in −5°C storage, 16 wk in −10°C storage, and 48 wk in −15°C storage. Sensory chewiness increased initially, then remained constant with storage time except in −15°C storage. Generally, the lower storage temperature resulted in less sensory chewiness. The correlation coefficients (r) between sensory and objective measurements for tenderness and chewiness were 0.76 and 0.88 (P < 0.05), respectively.

Pea samples were collected after various unit operations in a commercial cannery and the vitamin C losses at these points were investigated. Blanching and retorting accounted for the major losses. A substantial amount of vitamin C in peas leached into the brine. Approximately two-thirds of the original vitamin C in fresh peas was lost during processing. Shelled peas were also blanched in steam, water, and in an agitated water system under laboratory conditions. Vitamin C retention in water-blanched peas appeared to be independent of agitation rate, indicating that diffusion may be the controlling mechanism. The diffusivity of vitamin C in peas at 85°C was estimated to be 1.4 × 10−4 cm2/sec.

Purple hull pinkeye southern peas were harvested at three levels of maturity, shelled and stored at three temperatures (1, 5, and 20°C). Samples were evaluated at three storage intervals (1, 4 and 7 days) using 11 different indicators of quality. Alcohol insoluble solids and total solids measurements were most closely related to maturity differences. Derived instrumental color functions (AH and AE), pH, total acidity, and % green peas were the quality indices providing the best separation of the effects of maturity and storage. Instrumental color values were more ciosely correlated to changes in % green peas than total chlorophyll concentration. The proposed indices provide the means for a unified study of quality changes in sourthern peas during all stages of postharvest handling.

Peroxidase isoenzymes were purified from green peas with ion-exchange chromatography on DEAE- and S-Sepharose. Three isoenzymes were identified, one neutral (N) and two cationic (C1, C2). N was extremely heat labile, with 50% original activity lost after heating 1.5 min at 25°C. N had Km values (pH 5.0) of 10.2 mM and 2.6 mM for guaiacol and H2O2, respectively. C1 and C2 retained activity on heating at 30–70°C. C1 was able to reactivate after thermal inactivation. Km values for guaiacol/H2O2 were 10.8 mM/7.2 mM (pH 5.0) and 10.8 mM/4.3 mM (pH 6.0) for C1 and C2, respectively. The three isoenzymes exhibited different peroxidase activities with different H-donors, different sensitivities to cyanide and different abilities to catalyze oxidation of indoleacetic acid.

Equations were developed for prediction of freezing times of foods of slab geometry, for three different boundary conditions, using a method of solving for enthalpy per unit volume instead of temperature. Experimental verification was performed for the operation with a convective heat transfer boundary condition, using ice cream and green peas in a granular packed bed as test materials. Results indicate good prediction of freezing times over a range of conditions. Results of thawing tests are less satisfactory if the ambient temperature lies in the zone of rapidly changing food properties. A comparison with literature predictions is presented.

A model for predicting freezing times of individual particles is adapted to operating conditions of fluidized beds. The equation is linked to a model for movement of solids along the continuous fluidized bed which includes longitudinal mixing. The equations obtained allow the design and optimization of fluidized bed freezers. Calculations are performed for beds of green peas. Maximum values in the production rate are found in terms of bed dimensions and operating conditions. A nomogram is provided to facilitate equipment design under conditions of maximum production rate and minimum blower power consumption.

Structure-digestibility relationship was investigated in in vitro model systems for phaseolin and vicilin, the major 7S storage proteins of dry bean and green peas, respectively. Native phaseolin was more resistant to trypsinolysis than vicilin, while heating caused a reversal of proteolysis rates. Conformational studies using far-uv and near-uv CD spcctroscopy suggested the native conformatin of vicilin to be far more flexible to thermal treatment and SDS-induced environmental changes; however, neither the thermal treatment nor the anionic detergent caused a complete randomization of structure in either proteins studied. Ironically, the flexible native conformation of vicilin seemed to induce greater undesirable changes upon heating so as to confer resistance to proteolysis. The possible role of secondary and quarternary structures of these two proteins is descussed in relation to their digestibility.

SUMMARY— The activity of the enzyme lipoxidase and the concentrations of free and lipid-bound fatty acids in different parts of green peas were determined. The extractable enzyme was found mainly in the cotyledon, where its concentration was also highest. The concentration of the enzyme was somewhat higher in the inner than in the outer part of the cotyledon. Both free and bound fatty acids were found in all parts of the pea. The oxidation rate of linoleic acid, catalyzed by lipoxidase, was found independent of oxygen partial pressures above about 20 mm Hg. The respiratory rates of intact and damaged green peas were determined. Based upon these data and on plausible diffusion coefficients, an attempt was made to calculate the oxygen conditions in green peas.

Samples of the outer portions of fresh beets, broccoli, cabbage, carrots, cauliflower, corn, head lettuce, leaf lettuce, mushrooms, and potatoes, as well as frozen green beans, green peas, pea pods, and spinach were examined for the presence of Listeria monocytogenes using a 7-day enrichment procedure at 30°C. Samples were streaked on modified McBrides agar, and isolates were tested for characterization reactions. Fresh carrots, lettuce, and mushrooms, and frozen spinach were also examined using a cold enrichment procedure at 4°C. Samples were taken weekly, streaked onto modified McBrides agar, and were characterized. It was determined that no L. monocytogenes was detectable in any of these samples.

The influence of thermal processing (canning) on the carotenoid content of carrots (Daucus carota) and green peas (Pisum sativum) was investigated. Carotenoids extracted from fresh and canned vegetables were separated by column chromatography and quantified using spectrophotometric analysis. Canned canots and green peas had a higher carotenoid content than fresh samples. The apparent increase in canned carrots was mainly due to the loss of soluble solids into the brine during processing. However, the increase of carotenoids in canned green peas was due to the loss of carotenoids by enzymatic activity in fresh green peas during extraction procedures.