The effect of storing cooked Bengal and Cypress milled rice at -13, 3, 20, and 36°C on texture and degree of starch retrogradation was investigated. Cooked rice firmness increased, while stickiness decreased, during storage at -13 and 3°C. Starch retrogradation, measured with a differential scanning calorimeter, was observed for both cultivars during storage at -13 and 3 °C, but not at 36 °C.At 20°C, retrogradation occurred in Cypress, but not in Bengal. Starch retrogradation showed positive linear trends with firmness for both cultivars at all storage temperatures (R 2 = 0.80) and with stickiness for Bengal stored at -13 and 3 °C and for Cypress stored at 3 and 20 °C (R 2 = 0.88).

Chilling injury symptoms do not appear in nonripe peaches (Prunus persicu L.) while stored at low temperatures, but a dry-mealy texture (woolliness) appears in chili-injured fruits after ripening. Reduced pectinesterase and polygalacturonase activities were associated with reduced juiciness, reduced levels of water soluble pectins, poor texture and enhanced levels of insoluble pectins in peaches which were ripened after storage at 1°C for more than 3 wk. Pectinesterase and polygalacturonase activities and levels of pectic substances were unaltered in nonripened fruits held at 1°C. Fruits transferred to 20°C for 24 or 48 hr after 1 and 3 or 2 and 4 wk of storage at 1°C did not exhibit woolliness after 5.5 wk of storage. Warming for 12 hr was inadequate to prevent the development of woolliness. The effect of intermittent warming on providing a desirable texture in subsequently ripened fruits was related to enhanced pectmesterase and polygalacturonase activities. Low temperatures appeared to induce this physiological disorder by reducing the capacity to provide adequate levels of pectinesterase and polygalacturonase during subsequent ripening at nonchilling temperatures. Intermittent warming appeared to prevent injury by protecting the capacity to produce adequate levels of pectolytic enzymes during ripening.

The effects of brine treatments (CaCl2 and NaCl) and storage on pectic substances and texture of cucumber pickles were examined. Firmness of cucumber pickles was closely associated with the solubility characteristics and degree of esterification (DE) of pectic substances. Brining, storage, time of CaCl2 addition and concentration of NaCl and CaCl2 were all observed to influence the characteristics of pectic substances. Important to preventing softening was maintenance of pectic substances not extractable (NXP) by conventional methods, i.e., by water (WSP), the chelator sodium hex‐ametaphosphate (CSP), and dilute alkali (OHSP). Erosion of NXP consistently resulted in increased levels of CSP and reduced firmness. Reducing the amount of demethylation of pectins was also associated with maintaining firmness. Although the DE declined rapidly during brining, tissues from treatments that enhanced firmness had pectic substances with the highest DE. CaCl2 added to brine at the beginning of fermentation was most effective in preventing the demethylation of pectins and solubilization of NXP. In contrast, delayed addition of CaCl2 and storage in low NaCl concentration (5% or less) caused greater pectin demethylation, erosion of NXP with concomitant increases in CSP and tissue softening.

Changes in cell wall pectic substances, degree of pectin methylation, bound Ca++, neutral sugar composition, and firmness were determined in mesocarp tissue of pasteurized and nonpasteurized fresh pack cucumber pickles. Large changes in solubility characteristics of pectic substances occurred in cell walls of nonpasteurized pickles that were attenuated by pasteurization. In particular, water and alkali soluble pectins declined, and nonextractable pectins increased during the first month of storage. The major changes in pectic substance solubility appeared to be related to reductions in the degree of pectin methylation with a minor influence of CaCl2. Galactose in cell walls of nonpasteurized pickles was substantially reduced, and the reduction in galactose was hindered by CaCl2 or pasteurization. The amount of bound Ca++ appeared to be associated with tissue firmness after one month in storage, since firmer tissue had more cell wall bound Ca++. While firmness was associated with the amount of bound Ca++, the amount of bound Ca++ was dependent on the supply of Ca++ and the degree of pectin methylation.

Alkaline degradation of the pigments curcumin (CC), demethoxycurcumin (DMC) and bis-demethoxycurcumin (BDMC) in aqueous solutions of purified and commercial oleoresin sources was investigated. Alkaline degradation of the compounds corresponded to pseudo-first-order kinetics. Responses were similar for pigments combined or alone in solutions. Profiles of rate constants were closely associated to polynominal curves. Degradation rate constants rapidly increased from pH 7.45 to a maximum at about 10.2 and then tended to decline at higher pH. Rates of alkaline degradation were lower for BDMC than for CC and DMC. Halflives of CC, DMC and BDMC at pH 7.45 were 900, 1700 and 2200 hr, respectively. In contrast, half-lives of CC, DMC and BDMC at pH 10.2 were 0.4, 1.0 and 5.0 hr, respectively. Use of BDMC instead of CC in alkaline foods would be expected to improve color stability.

The effects of calcium ions and the cheluting agents EDTA and citrate on the ability of partially-purified polygalacturonase (PG) from ripe tomato fruit to degrade polygalacturonate, preparations of isolated middle lamellae and cell walls (ML-CW), and outer pericarp tissue from tomatoes were examined. The inhibition of degradation by calcium ions was counteracted by the presence of EDTA or citrate, and these chelating agents also reduced the resistance to attack by PG on ML-CW and tomato pericarp tissue. Degradation by PG of ML-CW and pericarp tissue from all ripeness stages was stimulated by chelating agents. Susceptibility of fruit tissue containing the nonripening (nor) gene to degradation by PG was similar to that shown by normal mature green fruit tissue. With increasing maturity of the mutant fruit, resistance to degradation declined, but not as rapidly as with normally ripening fruit. It appears that calcium associated with the ML-CW and its removal regulate the rate and extent of degradation by PG during normal tomato fruit ripening. 'Published with the approval of the Director of the Arkansas Agricultural Experiment Station, University of Arkansas, Fayetteville, AR 72701.

Cucumbers were fermented and held for 30 days in equilibrated solutions containing low NaCl (11-13" salometer) and high NaCl (18.5-20.5" salometer) with and without CaCl, and/or polygalacturonase (PG). CaCl, and PG treatments did not interfere with fermentation. Separately, CaCl, enhanced firmness of pickles while PG was effective in causing excessive softening. When CaCl, was present in PG containing solutions, softening by PG was inhibited.

Factors affecting the production and stability of (E, Z)-2, 6-nonadienal (NDE) from pickling cucumbers were examined. Production capability was rapidly destroyed in tissues exposed to freezing, fermentation or processing conditions. Lower concentrations were produced by exocarp tissues than mesocarp or endocarp tissues, which probably accounted for an almost linear relationship between fruit size and NDE production. NDE production was reduced by acidification, enhanced by linolenic acid, and unaffected by other unsaturated fatty acids NaCl or CaCl 2 . E-2-nonenal production was suppressed when NDE production was increased by linolenic acid. NDE was unstable in filtrates of homogenized tissues. Its stability was substantially improved by acidifying to pH 2 and unaffected by CaNa 2 EDTA. Extraction and concentration by vacuum distillation further enhanced stability. Loss of NDE in distillates averaged 0.3%/d during storage at 5 8C.