SENSORY QUALITY OF GALA APPLES AS INFLUENCED BY CONTROLLED AND REGULAR ATMOSPHERE STORAGE

The sensory quality of Gala apples stored for up to 4 months in delayed controlled atmosphere (CA), regular atmosphere (RA), and a combination of sequential CA and RA storage (CR) was evaluated. Sensory analysis included difference and acceptance testing. Firmness, soluble solids and titratable acidity contents, and volatile flavor profiles were measured analytically. Acceptability decreased with storage time. Apples stored in RA were more acceptable than apples stored in CA or CR; the differences between storage treatment were not significant after 4 months of storage. Firmness decreased with storage time, but was not affected by storage treatment. Soluble solids and titratable acidity contents were not affected by storage treatment or time. Storage treatment, storage time, and lot had a significant effect on the volatile flavor profiles. CA storage and extended storage contributed to decreases in the content of volatile flavor compounds.     

STORAGE OF MINIMALLY PROCESSED ROMAINE LETTUCE UNDER CONTROLLED ATMOSPHERE

The effects of CO₂ and O₂ concentration on the preservation of minimally processed Romaine lettuce (Lactuca sativa, L.) under controlled atmosphere were studied. The lettuce was stored at 4C for 16 days under a continuous stream of nitrogen containing 0.5 to 2% O₂ and 2 to 15% CO₂. Increasing the CO₂ content in the atmosphere to 10% or more reduced enzymatic browning due to wounding and improved lettuce visual quality. However, 15% CO₂ caused brown lesions (brown stain, BS) after 8 days of storage. Decreasing the O₂ content to 1% in the presence of 10% CO₂ reduced tissue browning slightly without lowering the content of phenols, but 0.5% O₂ increased browning and anaerobiosis. Among the atmospheres tested, 10% CO₂ and 1% O₂ were beneficial for maintenance of the quality of minimally processed Romaine lettuce.     

CHANGES IN THE ACTIVITY AND SUBCELLULAR DISTRIBUTION OF PPO IN 'DELICIOUS' APPLES DURING CONTROLLED ATMOSPHERE STORAGE

Polyphenol oxidase (PPO) activity in 4, 000 × g, 100, 000 × g, 200 × g and soluble fractions of ‘Delicious’ apples was monitored during 28 weeks of controlled atmosphere storage. PPO activity in 4, 000 × g and 100, 000 × g fractions decreased, while that in soluble and 200 × g fractions increased. These shifts in subcellular location occurred sooner in apples which were stored under high CO₂ conditions (2.5–6% O₂, 8–12% CO₂) than those under normal CA conditions (2% O₂, 3% CO₂). Polyacrylamide gel electrophoresis of 4, 000 × g fractions isolated from ‘Delicious’ apples at harvest showed 2 bands with PPO activity, while stored samples all had 3 bands. Isoenzyme patterns were found to vary in different subcellular fractions.     

EFFECTS OF MODIFIED ATMOSPHERE PACKAGING AND FILM ON SENSORY AND STORAGE PROPERTIES OF FROZEN HAM STRIPS

The effectiveness of modified atmosphere packaging and barrier properties of films upon the product attributes of frozen (IQF) ham strips, that are normally found at salad bars, was studied every 28 days over a period of 196 days. Three gases/mixture were used (CO₂, N₂ and ambient air) for flushing two pouches, one made from normal barrier film (861) and the other from a high barrier film (863). A triangle test and sensory evaluations were performed by a semi-trained panel (six members) for the following traits: freshness, structure, mouth feel, overall evaluation, aroma, appearance and off-flavors. Overall evaluation scores were acceptable up to 140 days of storage, regardless of the pouch used, but from 140 to 196 days, the product would be only marginally acceptable. Ham strips stored in N₂ or CO₂ atmospheres had a higher acceptance level than those stored frozen in ambient air. Panelists distinquished between fresh and stored product more frequently (75%) when the product was stored in ambient air pouches rather than CO₂ or N₂ atmospheres. Pouches made from the higher barrier film had lower (398/g) total aerobic plate counts than pouches (736/g) made from normal barrier film, but these counts are low and would be acceptable in industry.     

INFLUENCE OF FLOAT MATERIALS ON THE QUALITY OF 'd'ANJOU' PEARS AFTER REGULAR AND CONTROLLED ATMOSPHERE STORAGE

Thirty bins of commercially harvested 'd'Anjou' pears from each of three growers were packed at a commercial packing facility, using either of two pear float materials and wrapping the pears in one of three paper wraps. Float materials used were potassium phosphate (XEDA-F, pH 11.3) or lignin sulfonate (lignosite), the industry standard. Paper wraps were impregnated with either Biox-A, 3% oil + copper and ethoxyquin (3% C&E), or 6% oil + copper and ethoxyquin (6%C&E). After packing, 36 boxes were placed in regular atmosphere (RA) storage at 1C. Seventy-two boxes were placed in controlled atmosphere (CA) storage (1.5% O₂ and 1.0% CO₂ at OC). After 50 days (RA) or 100 and 200 days (CA) storage, fruit was removed and quality evaluated. Float material (Lignosite or XEDA-F) did not influence either objective or subjective quality under either RA storage or up to 200 days CA storage. Type of paper wrap did have a strong influence on pear quality, particularly affecting scald rating and subjective ratings of pear quality. Paper wraps containing Biox A produced pears of reduced quality compared to papers with either 3 or 6% oil with C&E, which were comparable in quality.     

QUALITY OF 'ANJOU' PEARS AFTER DIFFERENT TYPES OF CONTROLLED ATMOSPHERE STORAGE

‘Anjou’ pears (Pyrus communis, L) were subjected to seven different controlled atmosphere (CA) storage practices and stored at 1C, for 90, 150 or 210 days plus 30 days at regular air atmosphere (RA). CA storage treatment conserved pear qualities to a certain extent regardless of storage treatment. Establishment of CA conditions (2% O₂ and < 1 % CO₂ on warm pears (20C), prior to cooling, resulted in reduced firmness, finish and color and increased amount of scald, shrivel and physiological disorders. Pears held in CA storage (2% O₂ and < 1 % CO₂) for 90 days and an additional 30 days in RA storage maintained good quality. When held for longer storage periods, firmness, finish and color decreased, and scald, shrivel and physiological disorders increased.     

SENSORY, NUTRIENT AND CHLOROPHYLL CHANGES IN BROCCOLI FLORETS DURING CONTROLLED ATMOSPHERE STORAGE

Sensory (color, turgor, decay) and nutritional (vitamin C, β-carotene) quality of broccoli florets were evaluated during storage at 4C in air or under a controlled atmosphere containing 2% O₂+ 6% CO₂ (CA). Shelf-life, green color and chlorophyll retention were greater under CA than in air, although loss of stem turgor was accelerated. All samples stored in air had decayed sufficiently by the fourth week to be unfit for consumption, while samples stored under CA showed a few spots of decay after five weeks. However, CA was associated with browning at the cut surface of the stem. Retention of vitamin C was slightly greater in CA than in air, while β-carotene content increased at the end of CA storage. Returning the samples to ambient conditions for 24 h after storage under either conditions resulted in chlorophyll and vitamin C losses, whereas β-carotene content remained stable.     

RHEOLOGICAL AND SENSORY QUALITY OF READY-TO-BAKE CHAPATTI DURING FROZEN STORAGE

The effect of prolonged frozen storage at − 18C, on the textural and sensory properties of ready-to-bake frozen chapatti (R-BFC) was evaluated. The R-BFC samples were prepared from normal- (control) and microwave-treated (18% moisture content for 80 s) wheat grains. Results showed that the extensibility of dough and maximum load for resistance increased gradually in both the samples during frozen storage; however, the increase was lesser in the treated ones. Chapattis prepared from both R-BFC samples exhibited higher hardness, cohesiveness, chewiness and lower springiness values during frozen storage. Microwave-treated R-BFC samples were rated as better retained in color, texture and overall acceptability scores as compared with control, up to 6 months of storage at − 18C. Thiamin and riboflavin contents were monitored during frozen storage and a loss of 12.0–14.5% in thiamin and 4–6% in riboflavin after 6 months of frozen storage was recorded.

PRACTICAL APPLICATIONS

During frozen storage, various physical, rheological and sensory changes occur in the food products, which determine the consumer's acceptability. The results of this study will help to establish quality of the frozen chapattis with respect to texture, color and aroma which will meet the consumer's acceptance. The protocol for the storage of frozen chapattis will help the industry to deliver the product of optimum quality.     

CHEMICAL, NUTRITIVE AND SENSORY CHARACTERISTICS OF TOMATOES BEFORE AND AFTER CONVENTIONAL AND MICROWAVE BLANCHING AND DURING FROZEN STORAGE

The objective of this study was to evaluate the effects of microwave blanching on chemical, physical and sensory characteristics of tomatoes prior to and after frozen storage. Tomatoes were blanched (4 min) using four treatments: conventional boiling water (BW), steam (ST), microwaved in a glass container (MW), and microwaved in boilable bags (MWB). The lowest moisture content occurred in MW‐blanched tomatoes before (92%) and after (86%) frozen storage. These tomatoes had the highest reduced ascorbic acid (RAA) content and the highest RAA retention (> 23 mg/100 g, >91%) after blanching and after frozen storage. After blanching, MWB‐blanched tomatoes were the lightest, while after frozen storage, ST‐blanched tomatoes were the lightest. BW‐blanched tomatoes had generally higher flavor, texture and appearance scores. This study demonstrated that though visual color and sensory attributes were highest for BW‐blanched tomatoes, MW‐blanched tomatoes retained more nutritive value in the finished product.     

HEADSPACE GAS CHROMATOGRAPHY AND SENSORY ANALYSES OF BUCKWHEAT STORED UNDER CONTROLLED ATMOSPHERE1

The composition of volatile components in freshly-milled buckwheat flour produced from seed stored under controlled atmospheres (97% N₂ 1.5% O₂ and 1.5% CO₂) for 1 year was studied using capillary gas chromatography, mass spectrometry, sniffing port analysis, and sensory evaluation. Twenty-five volatiles were identified from over 100 compounds removed from the flour by a novel dynamic headspace technique and separated by capillary gas chromatography. Eighteen odor-active regions were detected but none were characteristic of the typical buckwheat flour aroma. The concentration of the major buckwheat volatiles decreased with storage of the seed under low O₂ and high CO₂ levels. The content of two of the odor-active volatiles, hexyl acetate and 1-hexanol, however, increased up to 4 fold in samples stored under controlled atmosphere for 60 weeks.     

SENSORY CHARACTERISTICS OF CONTROLLED ATMOSPHERE- AND AIR-STORED ‘GALA’ APPLES1

‘Gala’ apples from two Summerland sites were harvested at two harvest dates for two growing seasons (1994, 1995) and stored for 6 months in air and controlled atmosphere (CA). At harvest maturity indices were recorded. After storage, flesh firmness, titratable acidity and soluble solids were determined and sensory attributes were evaluated by a trained sensory panel. In both years, analyses of variance showed apples picked at commercial harvest were significantly more crisp, firm, and sour and less fruity and sweet than apples harvested two weeks later. Apples stored for 6 months in CA were more crisp, firm, juicy and sour, had fewer off-flavors, and had greater overall acceptability than apples stored in air. Apples held at 1.2% O₂for 6 months were more crisp than apples stored at either 2.5% O₂ or 5% Q, while apples stored at 5.0% O were significantly less firm, juicy, and sour than apples stored using the other O₂ concentrations. Apples stored at either 1.2% and 2.5% O₂ had significantly more fruity flavor than apples stored at either 5.0% O₂ or in air.     

CONTROLLED ATMOSPHERE STORAGE AFFECTS QUALITY AND CHILLING SUSCEPTIBILITY OF CUCUMBERS

Controlled atmospheres (CA) maintained the quality of cucumbers better than conventional refrigerated storage at 5C. Elevated levels of CO₂ (3%) and decreased concentrations of O₂ (1 and 15%) also increased the tolerance of cucumbers to chilling exposure. The content of sugars, including fructose and glucose; and organic acids, particularly malic acid, were maintained at higher levels in CA-stored cucumbers than in air-stored samples. The respiration rates (measured as CO₂ production) of cucumber fruit during storage at 5C were markedly suppressed under CA conditions. Contrary to reports in the literature, CA storage was found to be beneficial in reducing chilling injury and maintaining cucumber quality.     

CONTROLLED ATMOSPHERE STORAGE AND EDIBLE COATING EFFECTS ON STORAGE LIFE AND QUALITY OF TOMATOES

Tomatoes at pink stage maturities were coated with Semperfresh^TM edible fruit coating which is composed of sucrose esters of fatty acids, sodium carboxymethyl cellulose and mono-diglycerides of fatty acids. One group of coated and uncoated tomatoes were stored at 23 × 2C under air atmosphere, another group was stored at 12C under air atmosphere and third group was stored at 12C, 93–95% RH in a controlled atmosphere (CA) containing 3% CO₂, 3% O₂ and 94% N₂. Samples of tomatoes were analyzed for firmness, weight loss, titratable acidity, pH, soluble solids, sugars, ascorbic acid and lycopene to examine changes in quality during storage. Semperfresh^TM edible fruit coating was found to be significantly effective at both storage temperatures (23 × 2C and 12C) in air to delay changes in firmness, titratable acidity, pH, soluble solids, sugars, ascorbic acid and lycopene. Semperfresh^TM fruit coating reduced fruit weight loss as compared to fruit without coating but the difference between coated and uncoated tomatoes was not significant. Shelf-life of pink tomatoes was increased 3 days at 23 × 2C and 6 days at 12C in air by coating. CA storage delayed compositional changes in tomatoes significantly as compared to air storage of coated and uncoated tomatoes. CA storage also had a significant potential for reducing weight loss and microbial spoilage. Tomatoes were stored 40 days in CA. Coated and uncoated tomatoes exhibited the same results in CA.     

EVALUATION OF MICROBIOLOGICAL, PHYSICOCHEMICAL AND SENSORY QUALITIES OF CHITOSAN TOFU DURING STORAGE

Tofu containing both low and high viscosity chitosan was prepared and changes in the microbiological, physicochemical and sensory properties of the tofu during storage were investigated. The colony forming units of mesophilic and psychrotrophic microorganisms in tofu containing high viscosity chitosan were markedly lower during storage than those in the control tofu as well as the tofu containing low viscosity chitosan. The _pH of the tofu samples increased during storage. The L and a values of the tofu, especially the control tofu, increased during storage. In the sensory test, the roasted nutty and beany aromas of the tofu decreased during storage. Instrumental analysis of hardness and chewiness of the tofu decreased during storage. Overall preference for the tofu gradually decreased during storage, but overall preference for the tofu containing high viscosity chitosan scored higher than the other tofu samples.     

EFFECTS OF GAMMA RADIATION ON NUTRITIVE AND SENSORY QUALITIES OF SWEET POTATO STORAGE ROOTS

Jewel and Georgia Jet sweet potato storage roots were treated with gamma radiation doses of 0.1, 0.5, 0.8, 1.5 and 2.0 kGy and compared to the untreated control. Analyses showed that ascorbic acid and starch decreased at 1.5 and 2.0 kGy. Total carotenoids in both cultivars were unaffected by radiation treatment. Gamma radiation caused softening of Jewel and Georgia Jet sweet potato roots and the texture score decreased at 1.5 and 2.0 kGy. Color was not affected by radiation in either cultivar and differences in L, a and b values were not observed. The total sugar content of the Jewel sweet potato was higher at 0.8 kGy than at other doses but for Georgia Jet it tended to increase as the radiation dose increased. The sensory evaluation test indicated that acceptability of baked sweet potatoes was severly affected by gamma radiation at doses of 0.5 kGy and above.     

EXTENDED STORAGE LIFE OF LITCHI FRUIT USING CONTROLLED ATMOSPHERE AND LOW TEMPERATURE

The postharvest quality of litchi (Litchi chinensis Sonn.) cv. Bombay stored under controlled atmosphere (CA) at 3.5% O₂and 3.5% CO₂, 2C temperature and 92–95% relative humidity was studied. Fruits were also held in regular atmosphere (RA) maintained at 2C temperature and 92–95% relative humidity. Fruits kept at normal ambient conditions were used as controls. Various quality attributes measured revealed that fruits stored in CA exhibited Hunter “a” values of 11.2 after 56 days of storage, indicating the beneficial effect of CA on retaining the red color of litchi fruits. Fruits held in RA exhibited Hunter “a” values (7.9) lower than that of CA‐stored litchi, showing that browning of litchi was noticeable in RA. Loss of weight was lowest (4.9%) for the fruits stored in CA compared to those stored in RA (11.0%) and control (33.1%). Loss of acidity and ascorbic acid content of fruits stored in CA were less than that of RA. The smallest increase of litchi firmness and pericarp puncture strength of 2.2 and 3.9 times of initial level, respectively, were observed even after 56 days of storage in CA. Total soluble solid of litchi increased from 19.3° Brix at harvest to 23.0° Brix until 48 days of storage in CA after which it declined to 22.8 °Brix. The sensory evaluation of aril color and taste showed that the fruits held in CA were rated good throughout 56 days of storage.     

EVALUATION OF THE PHYSICAL AND SENSORY PROPERTIES OF JERKY PROCESSED FROM BEEF HEART AND TONGUE1

Eighteen beef jerky formulations (nine treatments, 3 muscle types X 3 cooking times X 2 replications) were prepared from USDA Good top rounds, hearts, and tongues obtained from a commercial source. Muscles were sliced, cured 3 days and cooked at 64 Cfor 12, 14 and 16 h. All treatments were evaluated for visual, sensory, chemical and cost analysis. Jerky produced from beef heart reduced final cost by 43%; however, visual and flavor properties of beef heart jerky were less desirable than jerky prepared from top round. Tongue jerky products were high in fat, extremely expensive and would be undesirable for today's health-oriented consumer. Top round beef jerky was the most desirable based upon sensory analysis, but heart jerky was highest in protein and lowest in fat. Further work may increase the possibility of reducing jerky costs by improving the color and flavor of beef heart jerky.