Search Results
Abstract
Light absorbance and random vibration techniques for estimating firmness of fruit of 4 cultivars of peach (Prunus persica (L.) Batsch) nondestructively were evaluated. The correlation between the Magness-Taylor probe pressure-test and the difference in light absorbance at 690 and 740 nm was significant for ‘Early Redhaven’, ‘Garnet Beauty’, and ‘Rio Oso Gem’. The correlation between pressure-test and random vibration data was significant for ‘Redhaven’ and ‘Garnet Beauty’. The linear regression equations differed with cultivar for both systems, but either system could be used to estimate firmness.
Abstract
A profile was developed to describe sensory characteristics of ‘Golden Delicious’, ‘Miller Spur’, ‘Redspur’, ‘Rome Beauty’, and ‘York Imperial’ apples (Malus domestica Borkh.). Ten sensory attributes were selected and the intensities of the attributes were plotted on a circular graph. The patterns of the plots differed among cultivars and patterns of some cultivars changed with successive harvests and storage of apples. The patterns were used to describe the general sensory characteristics of apples.
Abstract
Pressure test values obtained on various fruits with 2 manual fruit pressure testers (the Magness-Taylor and the smaller Effe-gi) and the Instron Universal Testing Instrument were compared. Tests were made on 5 apple, 1 nectarine, and 3 peach cultivars on an individual fruit basis. Differences in pressure readings were marked among instruments. Responses to the instruments differed among cultivars. Some apples were classified in different ripeness categories according to different pressure testers. For nectarines and peaches, high correlations, but not complete agreement, were obtained among instruments. For all 3 fruits, differences were sufficient to require specification of instrument and method of measurement when fruit pressure test values are reported and to necessitate compensation when measurements made with different types of instruments are compared. Regression equations such as we report should be used to permit accurate comparisons.
Abstract
The relationships among selected sensory textural attributes and data from modified Instron texture profile analysis (force/deformation curves obtained in compression of tissue cylinders) were examined for ‘Golden Delicious’, ‘Rome Beauty’, ‘York Imperial’, ‘Redspur Delicious’, and ‘Miller Sturdy Spur Delicious’ apples (Malus domestica Borkh.). Sensory crispness, hardness, and toughness were closely related to each other and to Instron texture profile forces at breakpoint (yield), failure, and 75% compression and to work energy in compression and rebound. Correlations of sensory attributes with the best single Instron texture profile variables were similar to those with Magness-Taylor penetration force (measured on an Instron); however, combinations of several texture profile variables in regression equations generally improved prediction of sensory attributes. Experimental Instron texture profile variables, especially force near midcompression, or the experimental variations on the customary variables, such as mean forces around failure and around full compression, were selected for prediction equations more frequently than the customary variables.
Abstract
The sonic vibration characteristics of 5 major apple (Malus domestica Borkh.) cultivars were evaluated. The resonant frequency (f) and the mass (m) of individual intact apples were measured over 4 weekly harvests and again after 2½ and 5 months in storage. A nondestructive index of firmness, f2m, for each apple was calculated and compared with other measures of fruit texture. The f2m index was directly correlated with Magness-Taylor pressure test measurements of firmness and with sensory ratings of crispness, juiciness, and firmness, especially crispness. It was inversely related to mealiness. Correlations were affected by differences among cultivars; results were best and most consistent for ‘Golden Delicious’ and ‘Rome Beauty’.
Postharvest CaCl2 pressure infiltration improves firmness and storage quality of apples but is still in the experimental stages. Its effectiveness could be increased if we had a better understanding of how Ca affects the tissue at the cellular level. `Golden Delicious' fruit were harvested from a commercial orchard and were pressure-infiltrated with CaCl2 (0%, 2%, or 4% w/v), stored for 6 months at 0C, and then for 7 days at 20C. Between harvest and the end of storage at 20C, the net breakdown of galactolipids and phospholipids decreased with increasing CaCl2 in infiltration solutions. During 0C storage, CaCl2-infiltrated fruit maintained greater concentrations of conjugated sterol lipids, and these lipid classes are thought to be closely associated with the plasma membrane. As membrane lipid alterations are viewed as a central factor in the senescence of fruits, Ca (from postharvest infiltration) may serve a major role in regulating fruit quality losses through its interactions with cell membranes.
Abstract
Correlations between sensory attributes and concentrations of headspace volatiles, soluble solids, and titratable acids of ‘Golden Delicious’ and ‘York Imperial’ apples (Malus domestica Borkh.) were examined. Stepwise regression analysis indicated that variation of sweetness of ‘York Imperial’ and acidity of ‘Golden Delicious’ and ‘York Imperial’ can be accounted for in part by soluble solids, titratable acids, and headspace volatiles of apples. Astringency, mustiness, starchiness, and floral-fruitiness correlated poorly with the volatiles, soluble solids, and titratable acids.
Postharvest Ca infiltration delays senescence and improves storage quality of apple fruit, but the consequences on membrane lipid composition have received little evaluation. We studied changes in galactolipids (mono- and digalactosyl-diacylglycerol; MGDG and DGDG) and sterol conjugates (sterol glycosides and acylated sterol glycosides; SG and ASG) in `Golden Delicious' cortical tissue. Fruit were pressure-infiltrated with CaCl, at harvest (0, 2, or 4% w/v), stored for 6 months at 0C, and evaluated during subsequent exposure to 20C. MGDG, SG and ASG concentrations were greater in Ca-infiltrated fruit (CIF) than in control fruit. A 35-37% increase in ASG occurred during the first 7 days at 20C in CIF, when ASG decreased by 19% in control fruit. Ca infiltration may delay degradation of plastid membranes and increase sterol conjugation during apple fruit ripening.
In 1993, we studied the postharvest behavior of 25 Rubus genotypes. Included in the study were named cultivars from Europe and North America, advanced selections from the Univ. of Maryland Cooperative Breeding Program, species and raspberry interspecific hybrids, with R. phenicolasius, R. pungens oldhamii R sumatranus, and R parvifolius. Wide variation exists in the ethylene production rates of these genotypes. The difference between the lowest ethylene producer, R. phenicolasius, and the highest ethylene evolver, HTCC-6t (R. lasiostylus), was four orders of magnitude. Ethylene evolution rate and percentage mold were not correlated. Ethylene production and respiration rates were also measured using a flowthrough system. No single pattern was characteristic of all genotypes. Red raspberries were the highest ethylene producers and showed an ethylene and respiratory climacteric. Blackberries were low ethylene producers. Interspecific hybrids showed varied postharvest behaviors. The behavior observed in these interspecific hybrids may explain some of the conflicting reports on the postharvest behavior of blackberries and raspberries. In general heattolerant species such as blackberry, R. occidentalis, R. parvifolius exhibited lower rates of respiration and ethylene evolution than species from cool, temperate areas like R. idaeus.
Calcium is an important constituent of the cell wall and plays roles in maintaining firmness of fruit and reducing postharvest decay. The modification of the cell wall is believed to be influenced by calcium that interacts with acidic pectic polymers to form cross-bridges. Infiltrating apples with CaCl2 has been suggested as an effective postharvest treatment for increasing the calcium content. Three different methodologies were used to analyze the effects of calcium on the cell walls: 1) nickel staining of polygalacturonate on free-hand sections, 2) cationic gold labeling of anionic binding sites in the cell walls, and 3) analytical detection of calcium ions (40Ca, 44Ca) using a secondary ion mass spectrometry. The combination of these methods allowed us to directly visualize the cellular features associated with the infiltration of calcium. Treatment resulted in significant enrichment in the cell wall of the pericarp, transformed the acidic pectins in calcium pectates, and resulted in new calcium cross-bridges. Evidence now suggests that exogenously applied calcium affects the cell wall by enhancing its strength and reinforcing adhesion between neighbor cells; therefore, calcium infiltration delays fruit degradation.