INFLUENCE OF HIGH TEMPERATURE STRESS ON POSTHARVEST QUALITY OF PROCESSING AND NON-PROCESSING TOMATO CULTIVARS

Tomato fruits from a processing cultivar,‘Dorado’and a non-processing cultivar, ‘Star Pak’, were subjected to three prestorage heat treatments over a 5-h period under unshaded (34±2C), shaded (29±2C) and pre-cooled (20±2C) conditions followed by storage for 18 and 36 days at 20C. Terminal symptoms of heat injury and disease infection were evaluated in relation to changes in physical, physiological and chemical characteristics of the fruits during storage. Unshaded fruits demonstrated effects of heat injury resulting in reduced bioelectrical resistance, increased electrolyte leakage, increased total acidity and decreased total soluble solids during storage at 20C. Pre-cooling and shading proved to be effective methods to remove or prevent accumulation of field-heat and minimize heat injury. Pre-cooling was most effective, accounting for 28 % and 14% less infected fruits for ‘Dorado’and ‘Star Pak’, respectively, compared with unshaded fruits, after 36 days storage at 20C.     

SENSORY AND MECHANICAL ATTRIBUTES OF GEL TEXTURE

Eighteen experienced judges evaluated the texture of gels varying in gelatin concentration (22-45 g/L) in terms of firmness by oral and manual shear and compression, cohesiveness, and extent of breakdown in the mouth. Manual compression and biting with the front teeth discriminated well across gel concentrations. All sensory measures except extent of breakdown increased with gelatin concentration. Instron (IUTM) measurements showed that increasing gelatin concentration resulted in an increase in maximum force and force/deformation, but had little effect on deformation at yield and rupture or in elasticity and cohesiveness. Results from mechanical measurements varied with the type of force applied (compression, shear or puncture), the loading rate (50 or 200 mm/min), and the extent of deformation attained (40–90%). The highest discrimination across gel concentrations was achieved with shear force at a rate of 200 mm/min and at greater deformations. Sensory responses correlated most highly with the following IUTM measurements: (1) Compression forces at yield and at deformations of 70 and 85% at the higher crosshead speed; (2) Compression forces below the yield point at the lower crosshead speed; and (3) Shear forces measured at maximum deformation (90%) at 200 mm/min.     

POSTHARVEST QUALITY AND SENSORY ATTRIBUTES OF ‘BYRONGOLD’ AND ‘RUBYSWEET’ PLUMS1

Fruit from two new cultivars of plums, ‘Byrongold’ and ‘Rubysweet’ were harvested at three maturities. Maturity one and two were ripened for three and six days at 20C and 85% relative humidity to determine fruit quality characteristics during storage. Plums were separated into three maturity categories by delayed light emission. Fruit size, weight, hue angle, flesh firmness, soluble solids and concentration of sugars, organic acids and sensory attributes were determined to evaluate stroage quality of the fruit. Significant differences were found between cultivars for sucrose, glucose, fructose and sorbitol. Sugar concentrations varied within the same cultivar by maturity and storage times. In general, acid levels decreased as plums ripened. Panelists preferred “Byrongold” ripened for three days for tartness and juiciness and “Byrongold” ripened for six days for sweetness. “Rubysweet” ripened for three days was preferred for sweetness, tartness and juiciness. Significant differences were found in peel bitterness between cultivars and days ripened. Unripened maturity 2 ‘Byrongold’ and unripenedd maturity 3 ‘Rubysweet’ had the highest peel bitterness. Hedonic scores showed ‘Rubysweet’.     

INFLUENCE OF WOUND INJURY ON ACCUMULATION OF PROTEINASE INHIBITORS IN LEAF AND STEM TISSUES OF TWO PROCESSING TOMATO CULTIVARS

Serine proteinase inhibitor(s) and small amounts of cysteine proteinase inhibitor were detected in both leaf and stem tissue 48 h after mechanical injury to the lower leaf of 21–25 day old tomato cultivars (cv). Leaves accumulated about 2–15 times more trypsin inhibitor than stem tissue. Approximately 10 times more trypsin inhibitor (TIU) accumulated in plants held at 30C in continuous light compared to plants held under ambient greenhouse conditions after injury. Uninjured plants held at 30C under continuous light accumulated less proteinase inhibitor(s) than injured plants. Holding Bonnie Best in the dark at 30C for 48 h resulted in less inhibitor(s) accumulation in response to mechanical wounding than holding plants at 30C in continuous light. TIU/g tissue recovered from injured plants held at 30C under continuous light varied with cultivar, i.e., for leaves: Bonnie Best (33.61), Alta (21.00; 25.43), Castlemart (16.00; 13.17) and Halley (1.96); and for stems: Castlemart (8.29), Alta (4.47) and Bonnie Best (2.59). SDS-PAGE assayed for inhibitor activity revealed the main trypsin and chymotrypsin inhibitor(s) in injured leaves both had a molecular mass (Mr) of 19.1 KD on SDS-PAGE substrate gels. Treatment of the inhibitors with 2.0% SDS at 100C prior to electrophoresis revealed a second major trypsin inhibitor (Mr = 16.4 KD) and two additional major α-chymotrypsin inhibitors (Mr = 16.4; 6.2 KD).     

EFFECTS OF CULTIVARS, BLANCHING TECHNIQUES, AND COOKING METHODS ON QUALITY OF FROZEN GREEN BEANS AS MEASURED BY PHYSICAL AND SENSORY ATTRIBUTES

Effects of cultivars, blanching techniques, and cooking methods on the color, texture, and sensory characteristics of frozen green beans were investigated. Provider beans were firmer than the Contender cultivar following frozen storage and cooking when evaluated instrumentally and by a sensory panel. Microwave-blanched beans were harder according to Instron measurements, and sensory scores for firmness and toughness were higher than beans blanched by boiling water or steam. Green beans blanched or cooked by microwaves had grassy aromas and strong off-flavors that were not detected in those blanched or cooked by conventional methods. Microwave cooked beans were greener and firmer than those conventionally cooked.     

DETERMINATION OF SOLANINE IN TOMATO CULTIVARS

The solanine content was determined for various developmental stages of tormato fruit from machine-harvest and hand-harvest cultivars used in ČSSR. Solanine was determined by a gravimetric and spectrophotometric method in the raw pulp and in salads from green tomatoes. The solanine content decreased during fruit ripening. In none of the cultivars and developmental stages studied was the solanine content high enough to cause health problems. Green and immature fruit are suitable for preparation of various preserved products, especially salads, syrups, pulps, and marmalades.     

PHYSICAL–CHEMICAL AND SENSORY QUALITY EVALUATION OF GARLIC CULTIVARS

ABSTRACT

Physical–chemical quality of 14 garlic cultivars grown in Spain was analyzed, and the cultivars were classified into three types: purple, white and Chinese, in order to show the possible differences among them. The most useful instrumental color parameter to discriminate among the different types of garlic was lightness (L*). The high pH value of the purple‐type cultivar Moraluz, and the high content of d ‐glucose, d ‐fructose and total sugars of the Chinese‐type cultivars were quite remarkable. The consumer judges preferred the color and pungency of the purple‐type cultivar Morasol, while Chino Sprint stood out for its intense garlic odor. Finally, correlations between the physicochemical and the sensory parameters were studied. The red color intensity was correlated with lightness (L*) and with hue (h*); pH was correlated with chroma (C*) and moisture percentage was correlated with sucrose content.

PRACTICAL APPLICATIONS

One of the main objectives of this work was to advise growers on the selection of garlic seed. The data obtained in this work was sent to a regional research and advising agronomic center (Technical Agronomic Institute, provincial council of Albacete), where advice was given to local growers concerning the selection of the most adequate seeds, in terms of physical– chemical properties and consumer preference, plus agronomic performance (data not included in this article). The conclusions reached in this study will make an important contribution to the agronomic characterization of the garlic cultivars grown in Spain.

     

PSYCHOMETRIC SCALING OF SENSORY TEXTURE ATTRIBUTES OF MEAT

The nature of psychometric scaling is considered and serious limitations in the use of unidimensional scales for characterizing multidimensional properties are pointed out. It is suggested that the ratio estimation has definite advantages over the commonly used subjective estimate scaling in that statistical tests of validity can be applied. Ratio estimation scales can also be used to test and calibrate other types of scales. Furthermore, it is suggested that multidimensional scaling techniques are valuable in that they provide evidence on (a) validity of scales, and (b) dimensionality and configuration of underlying data on differences between products with multidimensional properties.     

RELATIONSHIPS BETWEEN PHYSICAL-CHEMICAL COMPOSITION OF RAW PEAS AND SENSORY ATTRIBUTES OF CANNED PEAS

Two pea cultivars (Citrina and Warindo) at four commercial sizes (superfine, very-fine, fine and middle) were selected for a study of their physical-chemical parameters of raw and sensory attributes after canning. To determine the relationships between the physical-chemical parameters and the sensory attributes, Principal Component Analysis (PCA) was applied. About 65% of the total variation in the physical-chemical parameters and sensory attributes was expressed by two PCA Factors. Mealiness was an important sensory attribute in determining the sensory quality of pea, and was related to tenderometric value, alcohol insoluble solids and starch content of raw seeds. General acceptance of canned peas by panelists was based on titratable acidity, green color and juiciness. Raw peas should be selected according to their dry matter, starch and titratable acidity, if they are to reach the consumer in an appetizing state when canned. This quality is mainly determined by general appearance, juiciness and flavor.     

QUALITY ATTRIBUTES, PECTOLYTIC ENZYME ACTIVITIES AND PHYSIOLOGICAL CHANGES DURING POSTHARVEST RIPENING OF NECTARINE

The postharvest ripening at 20C and 90–95% RH for 10 days of ‘Armking’ nectarine grown in a greenhouse was investigated over two seasons. Firmness, titratable acidity, ascorbic acid, pH and maturity index were all adequate to stablish the rate of ripening. However, soluble solids content and reducing and non-reducing sugars showed no significant changes. It took about 10 days for very early ripening fruit (100 g weight and 82 N firmness) and 6 days for normal early ripening fruits (115 g weight and 46 N firmness), both harvested at preclimacteric stage, to become eating ripe (near 20 N). Total weight loss and decay after 10 days was approximately 11%. During ripening there was a temporal coincidence among higher rates of ethyleneproduction, higher pectinmethylesterase (PME) and polygalacturonase (PG) activities, lower firmness and acidity and higher maturity index. PME and PG activities increased during ripening, with a highly negative linear correlation between activities of the two enzymes and firmness. In very early ripening fruit, PME activity was more closely related to softening than PG, whereas in normal early ripeningfruit, PG activity was slightly more closely linked to the loss offirmness than PME.     

EFFECT OF NATIVE AND LYOPHILIZED KEFIR GRAINS ON SENSORY AND PHYSICAL ATTRIBUTES OF WHEAT BREAD

Native and lyophilized kefir grains were added directly to bread dough or as a starter in sourdough. Because of inadequate leavening activity of kefir, yeast‐leavened breads were prepared. Kefir addition influenced the quality attributes and the shelf life of wheat bread. The pH of bread containing kefir decreased as compared to that in the control bread. The acidity of bread with kefir increased as compared to that in the control bread. An addition of kefir grains, regardless of the form, lowered the bread volume and increased the mold‐free shelf life from 4 (control) to 5–7 days. The addition of kefir grains in bread dough contributed to a milder taste, a more delicate yogurt‐like or dairy aroma. The breads made with sourdoughs containing native or lyophilized kefir grains scored higher for crumb quality number than breads made by directly adding kefir grains.     

MODEL PREDICTION FOR SENSORY ATTRIBUTES OF NONGLUTEN PASTA

Response surface methodology was used to predict sensory attributes of a nongluten pasta and develop response surface plots to help visualize the optimum region. Optimum regions of xanthan gum, modified starch, and locust bean gum were selected by overlapping the contour plots of sensory properties of nongluten pasta as compared with the control pasta. The formula of nongluten pasta that possessed the most desirable properties was xanthan gum at 40 g, modified starch at 35 g, locust bean gum at 40 g, tapioca starch at 113 g, potato starch at 57 g, corn flour at 250 g, and rice flour at 50 g. The quality of nongluten pasta could be improved by using different levels of nongluten starches and flours, and nonstarch polysaccharides.     

EFFECT OF PROCESSING ON NUTRITIONAL AND ANTINUTRITIONAL FACTORS OF MOONGBEAN CULTIVARS

Ordinary cooking of presoaked and unsoaked seeds of six cultivars of moongbean (Vigna radiata L.) lowered phytic acid, polyphenols, trypsin inhibitors and improved in vitro digestibility of protein and starch, and availability of Ca, Fe and Zn when compared to unprocessed seeds. However, the effect was more pronounced on ordinary cooking of presoaked seeds followed by cooking of unsoaked seeds and presoaked seeds alone. A significant increase in vitro digestibility of protein (34–48%), and starch (31–62%) may be ascribed to the reduced content of phytic acid (45–65%) polyphenols (34–70%) and trypsin inhibitor activity (42–55%) after ordinary cooking of presoaked seeds of moongbean cultivars. Therefore, ordinary cooking of soaked seeds was the most effective treatment in improving the nutritional quality of moongbean.     

GLYCEMIC AND PHYSIOCHEMICAL PROPERTIES OF FIVE COMMON COWPEA (VIGNA UNGUICULATA) CULTIVARS IN NIGERIA

The physicochemical and physiological properties of five commonly consumed cowpea cultivars in Nigeria were assessed. The cultivars examined included Sokoto, Patasco, Iron beans, Isiocha and Ife brown. Ife brown had the most interesting physiochemical properties. It had the highest blue value index of 51.2, highest emulsion capacity of 3.5 g/g and the shortest cooking time of 30 min. Sokoto took the longest cooking time of 62 min. The cowpeas had glycemic responses ranging from 131.4 to 227.5 mg/dL against 369.5 mg/dL for white bread. The values for the glycemic index (GI) of the cultivars were on the low side (0–55) with the exception of Patasco, which had an intermediate GI of 61.57. Ife brown was found to exhibit a defined sinusoidal blood glucose curve. The incremental area under the blood glucose curve for Ife brown was also the smallest (P = 0.05) among the cultivars. This indicated, within the limit of this experiment, that this cultivar exerted the least stress on metabolic blood sugars of volunteers. Ife brown is considered the best in terms of managing physiological changes in blood sugar.