QUALITY OF MINIMALLY PROCESSED APPLE SLICES USING DIFFERENT MODIFIED ATMOSPHERE CONDITIONS

Fresh sliced apples were packaged in air, under vacuum or in the presence of nitrogen or carbon dioxide-nitrogen atmospheres and stored at 4 and 20C up to 20 days. Changes in color and firmness and microbial growth were then evaluated at different storage times. The modified atmospheres (MAs) studied showed positive or negative effects on the quality retention of the packed apple slices depending on the indicator followed. Of the air packed samples, all the MAs studied were suitable in preventing enzymatic browning but they differently influenced the microbial growth. Firmness decay, which was scarcely affected by MAs, was sufficiently reduced under refrigerated storage conditions. Carbon dioxide-nitrogen and under vacuum packagings were the most effective in inhibiting microbial growth.     

INFLUENCE OF CHEMICAL TREATMENT ON QUALITY OF CUT APPLE (cv. JONAGORED)

The quality of a new variety of apple, ‘Jonagored’, after peeling and cutting was evaluated during ten days of storage in air at 4C. The objective was to evaluate the shelf-life of apple cubes by detecting the limiting parameter and to test the influence of different chemical dips on the cut apple quality with the aim of extending shelf-life. Color, i.e. browning at the cut surface, was found to be the critical quality parameter determining the shelf-life of the cut apple to less than three days. There were no significant differences between the dip treatments in measurements of CIE values. When apple cubes were treated with ascorbic acid, ascorbic acid plus calcium chloride or ascorbic acid plus calcium chloride and citric acid, the 0.75% ascorbic acid dip was found to be the most effective preservation treatment in terms of reducing color change of the cut surface. Both 0.75% ascorbic acid and 0.75% ascorbic acid plus 0.75% calcium chloride inhibited the loss of firmness of apple cubes. When citric acid was added to the dip treatment, there were color changes similar to those of the control.     

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.     

QUALITY OF MINIMALLY PROCESSED FRUITS AND VEGETABLES

Consumer demand for fresh fruits and vegetables coupled with a demand for convenience is fueling an interest in minimally processed products. Advances in packaging technology provide a potential for improved quality and extended shelf-life of these products, but little is known about the physiological, microbiological and nutritional consequences of minimal processing. Mass marketing and brand-label identification of these products will require a new perspective on shelf-life and quality assurance. A systems approach has been proposed as a framework for quality management of fresh and minimally processed product based on the concept of providing the consumer with optimum quality at purchase and consumption.     

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.     

QUALITY OF PINK TOMATOES (cv. BUFFALO) AFTER STORAGE UNDER CONTROLLED ATMOSPHERE AT CHILLING AND NONCHILLING TEMPERATURES

Greenhouse-grown pink tomatoes (cv. Buffalo) were stored in air or in a controlled atmosphere (CA) of 4% O₂ plus 2% CO₂, to study the effect of CA at chilling and nonchilling temperatures on fruit quality characteristics. Tomatoes could be stored in CA at 12C for three weeks with no major changes in fruit appearance. CA was effective in delaying color development and ripening at this temperature. The soluble solids content was lower after CA storage, but no significant differences in firmness, pH or titratable acidity were observed between storage in air or CA. Storage in CA at 12C was also effective in reducing decay. However, at 6C, fruit showed high incidence of decay after both air and CA storage. CA did not alleviate chilling injury symptoms relative to air-stored samples and may have caused CO₂ injury. Water loss was greater under CA at both temperatures.     

INFLUENCE OF OPERATING CONDITIONS ON SENSORY QUALITY OF MINIMALLY PROCESSED OSMOTICALLY DEHYDRATED GUAVA

Abstract The influence of solution temperature (T), process time (t) and pressure regimen (P) on the sensory quality of minimally processed, osmotically dehydrated guava was analyzed. The study encompassed these values of each independent variable: T-30, 40 and 50C; t-60, 120 and 180 min, and P-atmospheric pressure, pulsed vacuum (5 min under vacuum, then atmospheric pressure) and continuous vacuum. The product was sensorially evaluated for color, flavor and firmness. Results were processed by means of the Design Expert version 5 software. Temperature, time and pressure regimen were shown to significantly influence the product's flavor. No effect of the factors on the fruit's color and firmness could be demonstrated. At the cellular level the tissues of guava treated at 40C for 60 min under pulsed vacuum are not significantly altered.     

QUALITY OF APPLE SLICES PROCESSED BY COMBINED TECHNIQUES

The effectiveness of single pretreatments and combinations of pretreatments on the prevention of enzymatic browning during freezing and thawing of apple slices was investigated. The combinations of blanching and dipping, either of which alone could not control enzyme activity, were studied. Blanching of apple slices caused a significant decrease of firmness even before the freezing-thawing phase. The use of a “light” dip after a short blanch allowed the product to be cooled and helped the antioxidant agents (ascorbic and citric acids) to enter apple tissue. The anti-browning action of sodium chloride, even at very low levels in dipping solutions, was confirmed. Partial drying avoided the loss of firmness but negatively affected the color. “Mild pretreatments”, including partial drying, gave satisfactory results in terms of firmness and color.     

EFFECTS OF LONG-TERM STORAGE ON QUALITY OF PROCESSED FOODS

Experiments were conducted on the effects of long-term storage at 4.4, 21.1, and 37.8°C temperatures on nutritional quality, physicochemical characteristics and organoleptic quality of 8 food packets (ready to eat individual ration items processed in flexible retortable pouches) of ham and chicken loaf, beef steak, beef stew, frankfurters, fruit cake, pineapple slices, cheese spread, and chocolate brownies. At 37.8°C storage life of cheese spread, pineapple slices, beef stew, chocolate brownies and fruit cake was 12, 12, 30, 30 and 30 months respectively. Ham and chicken loaf, beef steak, and frankfurters were acceptable after 37.8°C storage for 54 months, but frankfurters were near the borderline of rejection. The browning is usually associated with the high temperature storage of high sugar foods. Meat products except beef stew are apparently more stable than others at high temperature storage. The high temperature storage resulted in drastic loss of thiamin and ascorbic acid, significant loss of riboflavin and niacin, and discoloration and rancidity. Despite the losses of quality observed in all food packets stored at 21.1°C for 54 months, they were acceptable. Storage at 4.4°C for 54 months had very little effect on quality of the food packets and were highly acceptable.     

ANTIOXIDANT ACTIVITY AND QUALITY OF MINIMALLY PROCESSED INDIAN CABBAGE (BRASSICA OLERACEA var CAPITATA)

The effect of different dip treatments and storage period on the antioxidant activity and biochemical quality of Indian cabbage for minimal processing was studied. A gradual decrease in total antioxidant activity was observed during storage at 6C with no detectable activity at the end of 9 days in all the dip treatments, except in treatments containing combination of ascorbic acid and citric acid, and ascorbic acid alone (10 g/L each). Possibility of considering antioxidant activity as a marker of shelf-life has also been proposed. Incorporation of ascorbic acid and citric acid in the dip water improved the overall appearance and retained the maximum antioxidant activity, ascorbic acid and total carotenoids. Based on the overall quality and appearance score, Golden Acre was found suitable for minimal processing with a shelf-life of 9 days.     

EFFECTS OF LONG-TERM STORAGE OF FOODS ON QUALITY OF PROCESSED FOODS II.

The effects of long-term storage at 4.4, 21.1, and 37.8°C on physicochemical characteristics, nutritional and organoleptic qualities of freeze-dehydrated ration items from Packet Long Range Patrol were studied. The items included beef hash, beef stew, chicken stew, spaghetti with meat sauce, chili con carne with beans, chicken and rice, pork with escalloped potato, and beef and rice. The freeze-dehy drated foods were stable in quality during storage at 4.4, 21.1, and 37.8°C. After 44 months of storage all freeze-dehy drated ration items were in acceptable condition.     

QUALITY OF MINIMALLY PROCESSED LETTUCE AS INFLUENCED BY PACKAGING AND CHEMICAL TREATMENT

Shredded lettuce was packaged in sealed bags of monooriented polypropylene (OPP) film and also in polyethylene (PE) trays overwrapped with a multilayer polyolefin (RD106) or plasticized polyvinyl chloride (PVC) film; and stored at 4C in a refrigerated case during 8 days. Chemical treatment by dipping in a 0.3% ascorbic acid /0.3% citric acid solution did not significantly affect changes in microbial populations or visual sensory attributes. Type of package was not a significant factor for microorganism populations, but was significant (p<0.001) for changes in gas composition and visual sensory attributes. The modified atmosphere within the packages changed from normal air composition to about 1.5% O₂/12% CO₂ for OPP bags and to about 17–18% O₂/1–2% CO₂ for PVC-PE trays and RD106-PE trays after 8 days of storage. The visual sensory quality of the product was retained better in OPP bags than in the other ones.     

POLYPHENOLOXIDASE ACTIVITY OF MINIMALLY PROCESSED 'JONAGORED' APPLES (MALUS DOMESTICA)

The influence of three chemical dips using ascorbic acid (AA), citric acid (CA) and calcium chloride (CC) on the polyphenoloxidase (PPO) activity and on the total phenolic content of minimally processed (MP) apple (Malus domestica, cv. Jonagored) during cold storage was evaluated and a potential relationship with enzymatic browning was investigated. An ascorbic acid dip (42.6 mM) of 5 min duration was the most efficient chemical treatment in reducing the PPO activity of apple cubes. A 92% inhibition was achieved after 7 days of storage at 4C. All treatments were advantageous in comparison to the control in reducing color changes. Color changes, determined by absorbance at 420 nm (soluble pigments) and lightness (L) (insoluble pigments) of apple cubes treated with ascorbic acid were correlated with total phenolic content. No correlation was observed between PPO activity and tristimulus color parameters, browning index or total phenolic content of AA‐treated apple cubes.     

CONTROLLED ATMOSPHERE STORAGE of MANGO FRUIT, MANGIFERA INDICA L. cv. RAD

Controlled atmosphere (CA) storage of mango fruit (cv Rad) was studied using two combinations of carbon dioxide (4 and 6%) and three oxygen levels (4, 6 and 8%). the fruits were evaluated at 5 day intervals for various quality attributes, incidence of pathogenic decay and sensory quality. All CA treatments slowed the yellowing of both peel and flesh. After CA storage, fruit were stored at 13, 20 and 30C and the ripening periods were 7, 3 and 2 days, respectively. the best CA storage was 4%CO₂/6%O₂ at 13C.     

QUALITY CHANGES OF FRESH-CUT HONEYDEW MELONS DURING CONTROLLED ATMOSPHERE STORAGE

Quality, physiology, and microbial population were monitored with honeydew cubes held in air or controlled atmosphere (CA) of 2% 0₂+ 10% CO₂ at 5C and 4%0₂+ 10% CO₂ at 10C. The CA was beneficial in maintaining quality of honeydew cubes. Quality deteriorated rapidly with concomitant increase in respiration rate during the latter half of the 6-day at 10C or 10-day at 5C shelf-life. The shear force of samples was maintained by CA at 10C, but the visual quality was poor when that benefit was still noticeable. At 5C, an effect ofCA was not noted because the low temperature did not allow the shear force to decrease. The bacterial population was less on honeydew cubes held in CA than in air. Modified atmosphere with these gas mixtures would be beneficial in maintaining quality and retarding microbial growth on honeydew cubes, but strict temperature control is essential to avoid anaerobic respiration.     

EFFECTS OF PEEL ADDITION AND STORAGE ON QUALITY OF GOLDEN APPLE (SPONDIAS CYTHEREA SONN) HOT SAUCES

Fresh, frozen or brined golden apple puree (Spondias cytherea) was utilized in hot sauces. The effects of puree, fruit peel addition, and storage on quality of sauces was investigated. Base formulation, (%) consisted of golden apple puree (50), water (25), vinegar (10), peppers (6), sucrose (4) aromatic spices (2), citric acid (1.1) sodium chloride (1.0), xanthan gum (0.8) and sodium benzoate (0.1). Processing of hot sauces was at85–90C for15–20 min followed by hot‐filling into glass bottles. Fruits were acceptable in 20% brine up to 6 weeks at28–31C. Physico‐chemical quality of sauces varied due ( >P <0.05) to fruit puree. Sensory quality did not vary (< P >0.05) in sauces with 0% or 5% peel, however, sauces of 100% peel were more yellow ( P <0.05), had lower total soluble solids ( P <0.05) and were less acceptable ( P <0.05). The shelf‐life of sauces was at least 90 days at28–31C or 5C.     

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.     

EFFECTS OF THE RATE OF HEATING ON APPLE AND PEAR FRUIT QUALITY

There is evidence that the rate of heating to meet quarantine security impacts fruit quality as well as insect mortality. Linear heating rates, of 4, 6, 8, 10, and 12C/h to treatment temperatures of 44 and 46C were used to treat 8 cultivars of apples (‘Delicious’, ‘Golden Delicious’, ‘Granny Smith’, ‘Fuji’, ‘Gala’, ‘Jonagold’, ‘Braeburn’, and ‘Cameo’) and two cultivars of winter pear (‘d'Anjou’ and ‘Bosc’). Fruit were stored, ripened, and tested for various quality parameters. Scald was controlled, firmness was higher in heat treated fruit, ripening was delayed but uniform in pears, decay organisms were suppressed, red fruit became redder and green fruit remained green, the Brix‐acid ratio (SS/TA) was either unchanged (‘Granny Smith’) or increased. Physiological disorders such as bitter pit were exacerbated by the heat treatment, requiring culling after treatment to avoid storage of fruit so affected.