Ascorbic Acid Retention in Shredded Iceberg Lettuce as Affected by Minimal Processing

The effects of slicing method, packaging atmosphere and storage temperature were determined on total ascorbic acid (TAA) content of modified atmosphere packaged shredded lettuce. TAA was extracted from the lettuce samples and levels were monitored using either titration with 2,6-dichlorophenolindophenol solution or an assay kit. Slicing affected (p<0.05) ascorbic acid retention in the order manual tearing > manual slicing > machine slicing. Flushing with 100% nitrogen increased retention (～5%, p<0.05) over packages with product modified atmospheres. Storage at 3°C increased retention (～20%, p<0.05) compared with storage at 8°C. Scores for product appearance generally followed losses of TAA in the lettuce (p<0.05).     

Sensory, Microbiological and Chemical Quality of Mini-Peeled Carrots as Affected by Edible Coating Treatment

The effect of three application rates of an edible cellulose-based coating on sensory, microbiological and chemical quality of mini-peeled carrots was studied during storage at 2°C. Carrots treated with edible coating had reduced levels of white surface discoloration, and higher sensory scores for orange color intensity, fresh carrot aroma, fresh carrot flavor, and overall acceptability than non-coated carrots. Edible coating treatment did not affect levels of total aerobic microorganisms, yeast, mold or lactobacilli. Oxygen, carbon dioxide and ethanol levels in packages, and sugar and soluble phenolic content of mini-peeled carrots were not affected by coating treatment. An edible coating application rate of 0.23–0.49 L/min protected against surface discoloration and retained quality during storage at 2°C.     

Steam Treatment of Minimally Processed Carrot Sticks to Control Surface Discoloration

The effects of steam treatment and storage at 2° on surface discoloration and phenolic changes in modified atmosphere packaged carrot sticks was studied. Steam treatment retarded surface discoloration, soluble phenolic and isocoumarin production and lignin formation. Heat inactivation of phenylalanine ammonia-lyase (PAL), peroxidase (POD), and syringaldazine oxidase (SOX) also occurred. Surface discoloration on nonheated samples was accompanied by elevated levels of soluble phenolics, lignin and elevated PAL, POD, and SOX activities over time. Control of surface discoloration by steam appeared to be related to retardation of phenylpropanoid metabolism.     

Carrot Pulp Chemical Composition, Color, and Water-holding Capacity as Affected by Blanching

Our objectives were to investigate the effect of blanching on nutrients, color, α- and β-carotenes, dietary fiber, and water-holding capacity of carrot pulp after juice was extracted. Carrot pulp contained 4-5% protein, 8-9% reducing sugars, and 5-6% minerals. Compared to the color of fresh carrot juice, pulp from blanched carrots retained redness color values better than that from unblanched carrots. Pulp contained from unblanched: 17% and from blanched: 31-35% of the total α- and β carotenes in the fresh carrots. Glucose and galacturonic acid were predominant sugars of the nonstarchy polysaccharides (NSP) in carrots. Pulp contained 37-48% total dietary fiber and had a high water-holding capacity (WHC), ranging from 9.42 to 10.52g water/g organic matter. Considering carotenes, WHC, and fiber content, carrot pulp products are a good source of dietary fiber.     

Chemical Composition and Color of Strained Carrots as Affected by Processing

The effects of processing line location, holding temperature prior to retorting (82.7, 87.8, and 93.3°C) and retort temperature (118.3, 121.1, and 123.9°C) on chemical composition and color of strained carrots was evaluated. Hunter L, chroma and hue values, and glucose and fructose levels decreased as strained carrots were transferred from batch to holding tanks. Strained carrots held in batch tanks at 93.3°C had less total soluble phenolics, glucose and fructose than those held at 87.8°C and 82.2°C. Carrots retorted at 123.9°C had lower Hunter L and chroma values, and greater levels of total soluble phenolics than those retorted at 118.3 and 121.1°C.     

Lignin Formation and Surface Discoloration of Minimally Processed Carrot Sticks

The effects of an ethylene absorbent and storage at 2°C on surface discoloration and phenolic changes in modified atmosphere packaged carrot sticks was studied. Lignin formation occurred and corresponded with development of white discoloration in storage. Phenylalanine ammonialyase and peroxidase activity were stimulated by slicing and both enzyme activities remained elevated during storage. Soluble phenolics increased during storage, while dry matter content decreased within 24 hr after processing and then remained constant during storage. Ethylene absorbents prevented accumulation of ethylene, but did not affect surface discoloration or lignification.     

Quality Changes in Fresh-cut Peach and Nectarine Slices as Affected by Cultivar, Storage Atmosphere and Chemical Treatments

The shelf-life of slices from 13 cultivars of peaches and 8 cultivars of nectarines, varied (between 2 and 12 days at 0°C). Controlled atmospheres of 0.25 kPa O₂ and/or 10 kPa or 20 kPa CO₂ extended the shelf-life at 10°C of ‘O'Henry’ or ‘Elegant Lady’ peach slices by 1–2 days beyond the air control. Low (0.25 kPa) O₂ acted synergistically with CO₂ levels of 10 and 20 kPa to induce fermentative metabolism as indicated by ethanol and acetaldehyde production. A 2% (w/v) ascorbic acid + 1% (w/v) calcium lactate postcutting dip resulted in limited reduction of cut surface browning and tissue softening in ‘Carnival’ peach slices.     

Effect of Vacuum and Modified Atmosphere Packaging on the Shelf-life of Liquid-smoked Swordfish (Xiphias gladius) Slices

ABSTRACT: Swordfish fillets, dry-salted and treated with liquid smoke, were sliced and packed in vacuum conditions and under modified atmosphere (MA) (5% O₂,45% CO₂, 50% N₂) and stored at chilled temperature (4°C) to determine the effect of different packaging on shelf-life. Sensory attributes, total volatile basic nitrogen (TVB-N), pH, lipid oxidation by thiobarbituric acid test, and microbiological counts were monitored during 45 d of storage. The TVB-N increased to levels recommended by European regulation at the time of sensory rejection, resulting as the most reliable parameter of quality decay. Lipid oxidation was low and microbial counts could not be correlated with quality decay. Sensory rejection (at least 50% of the assessors scoring =5 in a scale from 1 to 9) was sooner for MA-packed samples (12d) than for vacuum-packed ones (42d).     

Modified Atmosphere-packed Marinated Chicken Breast and Rainbow Trout Quality as Affected by Package Leakage

Marinated chicken breast pieces and sliced rainbow trout were packed in modified atmosphere and stored to measure effects of package leakage. The sensory shelf life of products decreased slowly but linearly as leakage rate increased, with exception of the appearance of sliced rainbow trout, which was not affected by leakage rate. The concentration of ethanol in head space was a potential indicator of spoilage and package leakage for both products. The presence of dimethylsulfide indicated spoilage of chicken fillet and acetone indicated leakage in sliced trout packages. A redox leakage color-indicator functioned properly in package lids.     

Quality Changes in Stored Raw Grated Beetroots as Affected by Temperature and Packaging Film

The effects of atmospheric composition and temperature on quality of grated beetroots were analyzed. Beetroots ( Beta vulgaris L.) were washed, grated and packaged in trays wrapped with two films of different gas permeabilities. Trays were stored at 0°C or 4°C for a week and then transferred to 20°C. Changes in atmospheric composition, pigment content, pH, titratable acidity and production of exudate were monitored. Shelf-life of grated beetroots was 7 d at 0°C and 3 to 4 d at 4°C. There was a notable decrease in pigment content during storage.     

Minimal Processing and Edible Coating Effects on Composition and Sensory Quality of Mini-peeled Carrots

Coating treatment did not affect fresh carrot flavor or aroma, sweetness, bitterness, harshness or taste preference. Total terpenoids declined 72% after 17 days storage, with the major loss occurring within 3 days after minimal processing. α- and β-carotene declined 18% and 14% within 3 days after minimal processing with no further loss. Peel tissue contained less β-carotene than phloem tissue, and its removal was not responsible for loss of β-carotene. The edible coating did not affect terpenoid or carotene content.     

箱式气调对甜樱桃贮藏及货架品质的影响

为研究自发气调保鲜技术对甜樱桃贮藏效果的影响,以莎米托、菊红、拉宾斯、雷尼为试材,分析它们贮藏期及货架2 d后果实品质变化规律。试验结果表明,应用塑料箱式气调保鲜技术后,甜樱桃果实贮藏期延长,莎米托、菊红贮藏56 d,拉宾斯、雷尼贮藏49 d时,货架期果实品质仍呈缓慢下降趋势,尚具有商品及食用价值,之后果实硬度、可滴定酸度下降迅速,果柄保鲜指数、果皮褐变指数加重。     

Color of Minimally Processed Potatoes as Affected by Modified Atmosphere Packaging and Antibrowning Agents

Minimal processing of potatoes was studied by using different treatments of cut potatoes in combination with modified atmosphere packaging. Different packaging materials and peeling methods were evaluated. An L-cysteine (0.5%) and citric acid (2%) mixture prevented browning of potatoes effectively. Active modification of the atmosphere inside the package was necessary to achieve extended shelf-life. Nitrogen flushing was more effective than other gas treatments with a highly permeable multilayered polyolefin packaging material. Hand peeling and lye peeling resulted in better quality, but abrasion peeling was undesirable for fresh potatoes. The shelf-life of the minimally processed products could be extended to nearly 3 wk under refrigerated storage.     

Texture and Rehydration of Dehydrated Carrots as Affected by Low Temperature Blanching

Whole carrots were blanched at four temperatures for five time periods, then blanched again for 6 min at 100°C. A control sample was blanched 8 min at 100°C. All samples were then dehydrated. Very slight differences in rehydration ratios between treatments were observed. The 50°C blanch gave a firmness equal to or less than the control for all blanch times. The carrots blanched at 55°C for 15, 30 and 45 min were less firm than the control while the 60 and 90 min blanched samples were firmer than the control. The 60 and 65°C blanched samples had significantly firmer texture than the control when blanch time was > 30 min. Blanching carrots for 45 min at 65°C increased firmness of the rehydrated product by 51% for uncooked and 27% for cooked.     

Frozen Carrots Texture and Pectic Compotients as Affected by Low-Temperature-Blanching and Quick Freezing

Carrots preheated for 2 hr at 60°C and then cooked became firmer than raw or cooked carrots. After preheating, the amount of high methoxyl pectin decreased, and low methoxyl pectin increased. Firmness of carrots decreased through freezing then thawing, but preheated carrots retained firmer texture than those blanched in boiling water. Quick-freezing resulted in better texture than slow-freezing. Loss in texture was accompanied by release of pectin. Slow-freezing accelerated release of pectin as compared to quick-freezing. Preheated carrots were slower in release of pectin. The degree of esterification of pectin substances in raw carrots decreased during preheating, freezing and thawing. Cell damage in quick frozen carrots was slight. Optimum preheating occurred with 30 min at 60°C or 5 min at 70°C. Preheating and then quick freezing were effective in improving texture of frozen carrots.     

Gas Concentrations in Modified Atmosphere Bulk Vegetable Packages as Affected by Package Orientation and Perforation Location

A perforated plexiglass package box was used to study the effects of package orientation and perforation location on gas concentration profiles during modified atmosphere packaging of broccoli (Brassica oleracea) florets. Three package orientations and perforation locations were studied. Two temperature conditions were studied namely: constant temperature at 2°C and variable temperature between 2 and 20°C. Package orientation and perforation location affected gas concentration gradients across the package. Placing the package in a vertical orientation with perforation at the top side, resulted in higher gas concentration gradients in the package. Lower gas concentration gradients were obtained when the package was placed in a vertical orientation with perforation at the lower side. Temperature variation resulted in gas concentration fluctuation in the package.     

Effect of Modified Atmosphere Packaging on Shelf-Life of Iced Fresh Hake Slices

Shelf-life of hake slices (Merluccius merluccius) stored in the ice state (2±1°C) under modified atmosphere packaging (MAP) conditions was determined by measurements of pH, total volatile bases (TVB) and trimethylamine (TMA) content, mesophilic and psychrophilic bacterial counts, malonaldehyde content, exudation, protein functionality and sensorial analyses (colour and odour). The effect of different gas mixtures were evaluated: (1) 40% CO₂, 50% N₂, 10% O₂; (2) 60% CO₂, 30% N₂, 10% O₂; (3) 40% CO₂, 30% N₂, 30% O₂; (4) 60% CO₂, 10% N₂, 30% O₂ and (5) air (control). Important differences were found between MAP-stored and air-stored hake slices. Shelf-life of hake stored under MAP conditions was two-fold extended. Bacterial growth wasinhibited, increases of pH, TMA and TVB were reduced, and alterations inprotein functionality were delayed, and off-odours were not noted in MAP-stored hake slices after 21 days storage. Significant correlations were found between TMA content and total viable count (TVC), as well as between apparent viscosity and exudation. Hake slices could be stored in the ice state under MAP conditions for about three weeks without an important loss of quality. Fish freshness, handling practices and initial bacterial load have an important influence of shelf-life of hake.     

Design of Rigid Modified Atmosphere Packages for Fresh Fruits and Vegetables

A procedure was developed for designing rigid MA packages for fresh fruits and vegetables that takes into account the change in total pressure inside the package. The procedure was demonstrated by designing a package for kiwifruit using available data. Some practical considerations in designing MA packages such as time to reach steady-state conditions, variation in respiration rate, film permeability, and changes in temperature were included. Small deviations in respiration rate and permeability could lead to large variations in steady-state gas concentrations.     

Carrot Juice Color, Carotenoids, and Nonstarchy Polysaccharides as Affected by Processing Conditions

Effects of processing variables on color, α- and β-carotenes, and non-starchy polysaccharides (NSP) of carrot juice products were investigated. Unblanched‘carrots produced the highest amounts of juice and lowest amounts of pulp. Compared to color of fresh juice, canned juice from acetic acid-blanched carrots retained redness best, and juice from unblanched carrots retained the least. Juice products from unblanched carrots retained highest total carotenes. Retorting, concentrating, and freeze-drying partly reduced juice product carotenes. In most cases, the reduced amounts from various processing methods were greater for β-carotene than for α-carotene. NSP contents of juice products ranged from 1.1 to 1.5%.     

Moisture Distribution and Microbial Quality of Part Baked Breads as Related to Storage and Rebaking Conditions

Storage conditions of part-baked brown soda bread were studied as related to changes of crust and crumb moisture during rebaking at in-oven temperatures of 180 and 200°C for 10–40 min. Baking loss during rebaking originated solely from the crust area, whereas the moisture content of the crumb remained constant. Packaging in an atmosphere of 40% CO₂ and 60% N₂ and storage at 4°C inhibited microbial contamination for 13 wk. The relationship of moisture content and water activity of part-baked breads followed the characteristic of a sorption isotherm and was mathematically described by either a quadratic or exponential function.