Mechanism of Surface White Discoloration of Peeled (Minimally Processed) Carrots During Storage

A proposed mechanism of white discoloration development on peeled carrots included both physical and physiological responses to wounding. The physical response is a color change due to reversible surface dehydration. This study was performed at 2.5 and 10°C using a mode1 system controlling relative humidity, at 33, 75 or 98%, and a commercial system with low-density polyethylene (LDPE) plastic film bags. The rate of surface discoloration increased with decreasing RH. When excess surface moisture was left on peeled carrots, rates of white development decreased sharply at all RH compared with a dewetted control. The same effects were observed on peeled carrots stored in LDPE bags. Carrots partially regained their original color when water-dipped, due to reversal of the physical response component.     

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.     

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.     

Control of Minimally Processed Carrot (Daucus carota) Surface Discoloration Caused by Abrasion Peeling

Abrasion peeling of carrots results in formation of a white lignin type material on the surface during storage. The degree of its formation was directly related to severity of abrasion during peeling. Dipping the peeled product for 30 seconds in a 70°C. Acidic or basic solution (citric acid or sodium hydroxide), retarded formation of the material. The low pH dip did not cause flavor changes.     

High Oxygen and High Carbon Dioxide Modified Atmospheres for Shelf-life Extension of Minimally Processed Carrots

The impact of high O₂+ high CO₂ modified atmospheres (MA), on the preservation of minimally processed carrots was studied. A combination of 50% O₂+ 30% CO₂ prolonged the shelf life of sliced carrots compared to storage in air by 2 to 3 d. When the carrots received a pre-treatment with a 0.1% citric acid dip and a sodium alginate edible coating prior to packaging, shelf life was extended by 5 to 7 d. Advantages and disadvantages of the proposed MA over previously recommended MA (1% O₂+ 10% CO₂), related to a range of physicochemical and microbiological characteristics of carrots are discussed.     

Discoloration Characteristics of 3 Major Muscles From Cattle During Cold Storage

ABSTRACT:  Discoloration characteristics of 3 major muscles (LD, Longissimus dorsi; PM , Psoas major; SM, Semimemebranosus ) from Korean native cattle (Hanwoo) were monitored during 7 d of cold storage at 4 °C. The muscles were obtained from 12 Hanwoo carcasses at 24 h postmortem. Meat color (CIE L *, a *, b *), myoglobin (Mb) concentration, chemical form, metmyoglobin (MetMb) reducing ability (MRA), mitochondria concentration, and thiobarbituric acid reactive substance (TBARS) were measured at 1, 3, 5, and 7 d of storage. Although there were no significant differences in CIE a * and b *-values between the 3 muscles at day 1, the values of PM muscle were significantly ( P < 0.05) lower than those of LD and SM muscles at day 5 and 7. PM muscle showed a rapid decrease in the oxymyoglobin (OxyMb) and an increase in MetMb, which resulted in a significantly ( P < 0.05) higher percentage of MetMb in PM muscle compared to LD and SM muscles. Also, the Mb and mitochondria concentration of PM muscle was significantly ( P < 0.05) higher than those of LD and SM muscles. However, there were no significant differences in MRA, pH, or TBARS between the 3 muscles during 7 d of cold storage. It was concluded that rapid discoloration (that is, MetMb accumulation) in PM muscle of Hanwoo could be due to its higher contents of Mb and mitochondria.     

响应面法优化胡萝卜奶皮工艺的研究

采用Box-Behnken中心组合响应面试验设计,研究优化胡萝卜奶皮的最佳工艺条件,建立保温温度、保温时间、冷却时间和胡萝卜汁的添加量对感官评分影响的二次多项回归模型,并验证回归模型的有效性。结果表明,胡萝卜奶皮的最佳工艺条件:保温温度66℃,保温时间5.8h,冷却时间7h,胡萝卜汁添加量116mL。此时模型预测感官评分值为89.65,验证试验结果为89.50,与模型预测值基本一致。     

Color Stability of Edible Coatings During Prolonged Storage

ABSTRACT: The yellowing rates of edible coatings were determined at 23, 40, and 55 °C at 75% relative humidity (RH). Whey protein isolate (WPI) coatings had lower yellowing rates than whey protein concentrate (WPC) and the same rates as shellac coatings. Hydroxypropyl methylcellulose (HPMC) coatings had the lowest yellowing rates. Zein coatings became less yellow during storage; however, their color was still pronounced. Activation energies and Q₁₀ values for the yellowing of whey protein coatings were similar to those previously reported for the browning of whey powder. The results indicate that WPI coatings can be used in place of shellac coatings when low-color development is desired. WPC coatings can be used to tailor color development of a food.     

Sulfite and Starch Affect Color and Carotenoids of Dehydrated Carrots (Daucus carota) during Storage

Sulfite and starch treatments influenced the quality of dehydrated carrots. Initially, redness of dehydrated carrots was high in sulfite-treated samples. Redness and total α- and β-carotenes decreased as storage time increased in all treatments. Starch-treated samples had a slower rate of carotene loss, and retained more (P < 0.05) red color than did control and sulfite-treated samples. When residual sulfite in dehydrated carrots decreased to ～≤200 ppm, its effectiveness in protecting carotene was not notable.     

Evaluation of Textural Properties and Microstructure During Storage of Minimally Processed Apples

ABSTRACT: Texture and microstructure of fresh‐cut Golden delicious apples were studied during modified atmosphere storage. Softening could be prevented during several wk under oxygen restrictive environments. Initial 100% N₂‐atmospheres and the use of bags with a permeability of 15 cm3 O₂/m2·bar·24h preserved cell structure from collapsing, thus being the best conditions to maintain the original texture of apples. First‐order kinetics fitted data with high accuracy. Firmness could be described by a simple 1st‐order model with rate constants of 6.3 × 10^‐3 to 8.9 × 10^‐3 d^‐1. Hardness, cohesiveness, gumminess, and chewiness also followed an exponential decay that could be modeled from fractional conversion kinetics.     

Effect of Hydroxypropyl Methylcellulose-Lipid Edible Composite Coatings on Plum (cv. Autumn giant) Quality During Storage

ABSTRACT 'Autumn Giant' plums were coated with edible hydroxypropyl methylcellulose-lipid composite coatings. The coatings consisted of beeswax or shellac, at 2 lipid content levels (20% and 60% dry basis). Weight loss of coated plums decreased as lipid content increased. No differences on weight loss were observed between uncoated and 20% lipid-coated plums, indicating that the natural waxes of plums are as effective as coatings having 20% lipid. Water-dipped plums experienced the highest weight loss. Fruit texture was not affected by coating after short-term storage at 20 °C. However, for prolonged storage at 20 °C, the coatings significantly reduced texture loss and internal breakdown compared to uncoated and water-dipped plums.     

Evolution of Quality Characteristics of Minimally Processed Asparagus During Storage in Different Lighting Conditions

ABSTRACT:  The effect of different types of lighting (white, green, red, and blue light) on minimally processed asparagus during storage at 4 °C was studied. The gas concentrations in the packages, pH, mesophilic counts, and weight loss were also determined. Lighting caused an increase in physiological activity. Asparagus stored under lighting achieved atmospheres with higher CO₂ and lower O₂ content than samples kept in the dark. This activity increase explains the greater deterioration experienced by samples stored under lighting, which clearly affected texture and especially color, accelerating the appearance of greenish hues in the tips and reddish-brown hues in the spears. Exposure to light had a negative effect on the quality parameters of the asparagus and it caused a significant reduction in shelf life. Hence, the 11 d shelf life of samples kept in the dark was reduced to only 3 d in samples kept under red and green light, and to 7 d in those kept under white and blue light. However, quality indicators such as the color of the tips and texture showed significantly better behavior under blue light than with white light, which allows us to state that it is better to use this type of light or blue-tinted packaging film for the display of minimally processed asparagus to consumers.     

Evaluation of Mass Exchange During Osmotic Dehydration of Plum Using Response Surface Methodology

Water loss (WL), solid gain (SG), weight reduction (WR) and shrinkage were quantitatively investigated during osmotic dehydration of plum using response surface methodology with the sucrose concentration (30–60g/100 g sample), temperature of sucrose solution (40–60°C) and immersion time (60–240 min). Experiments were designed according to Central Composite Rotatable Design with these three factors. For each response, second order polynomial models were developed using multiple linear regression analysis. With respect to water loss, solid gain, weight reduction and shrinkage, both linear and quadratic effects of four variables were found to be significant. In most cases, an increase of sucrose concentration, temperature and immersion time increased WL, SG, WR and shrinkage, except the increasing of immersion time for osmotic treatment has no effect on shrinkage. It was found that immersion time and temperature were the most significant factors affecting the WL during osmotic dehydration of plum followed by concentration of sucrose solution. This was also true for WR. Effect of temperature and time were more pronounced for SG than the concentration of sucrose solution.     

Antifungal Coatings on Fresh Strawberries (Fragaria × ananassa) to Control Mold Growth During Cold Storage

ABSTRACT: Chitosan (2%) -based or hydroxypropyl methylcellulose (HPMC) (1%) -based coatings were applied on fresh strawberries to evaluate their antifungal efficacies against Cladosporium sp. and Rhizopus sp. Potassium sorbate (PS) was also incorporated into coating formulas to evaluate any additional inhibitory effects on mold inhibition. Strawberries were inoculated with Cladosporium sp. or Rhizopus sp. at a level of approximately 10³ log colony-forming units (CFU) /g, coated with 2% chitosan, 2% chitosan containing 0.3% PS, or 1% HPMC containing 0.3% PS, and stored at about 5°C and about 50% RH up to 23 d for enumeration of mold, yeast, total aerobes, and coli forms. To assess antifungal activity of the coating materials in vitro, coating solutions were embedded into agar plates and the diameters of radial mold growth were measured after inoculation. In addition, weight loss of coated strawberries and water vapor permeability of the coatings were measured. No significant combined inhibitory effects between chitosan and PS on fungal growth on fresh strawberries were detected. However, significant combined inhibition activity was observed in in vitro testing when PS was formulated into chitosan. Antifungal activity of chitosan against Cladosporium sp. and Rhizopus sp. was not affected by the autoclaving process of coating solutions. Coating treatment also reduced total aerobic count, coliforms, and weight loss of strawberries during storage. Hence, chitosan can be used as a natural antimicrobial coating on fresh strawberries to control the growth of fungi, thus extending shelf-life of the fruits.     

Discoloration and lipid deterioration of farmed giant catfish (Pangasianodon gigas) muscle during refrigerated storage

ABSTRACT:  Discoloration and lipid deterioration of farmed giant catfish ( Pangasianodon gigas) muscle during 14 d refrigerated storage were investigated. Lipid deterioration, lipolysis, and lipid oxidation in both dorsal and ventral muscles increased as storage time increased. A progressive formation of primary lipid oxidation products monitored by the increase in conjugated dienes (CD) was observed ( P < 0.05) and the increase in thiobarbituric reactive substances (TBARS), an index of secondary lipid oxidation products, was noticeable throughout the storage ( P < 0.05). The pH of both dorsal and ventral muscles tended to increase as storage time continued ( P < 0.05). A gradual increase in free fatty acid (FFA) formation was found within the first 10 d of refrigerated storage ( P < 0.05), suggesting hydrolysis induced by lipases and phospholipases. However, a sharp decrease in FFA content was observed at the end of storage. Refrigerated storage also resulted in changes in redness index of both dorsal and ventral muscles. These changes were coincidental with the changes in metmyoglobin content. Therefore, the discoloration and lipid changes in giant catfish muscle during refrigerated storage depended on the muscle type and might be related to the difference in composition between dorsal and ventral muscles.     

响应面法优化腌制白萝卜贮藏过程中的抗褐变工艺

利用响应面法优化腌制白萝卜贮藏过程中的抗褐变工艺。通过单因素试验研究,筛选出抗褐变效果显著的3个因素:维生素C、柠檬酸、EDTA-2Na。以感评值和白度为响应值,通过响应面法对维生素C、柠檬酸、EDTA-2Na等三因素进行优化。结果表明,腌制白萝卜最佳抗褐变工艺:0.39%维生素C,0.31%柠檬酸,0.015%EDTA-2Na。实际测定值与理论计算值能很好地吻合。     

Comparison of the Cryoprotective Effects of Trehalose,Alginate, and Its Oligosaccharides on Peeled Shrimp (Litopenaeus Vannamei) During Frozen Storage

The cryoprotective effects of trehalose, alginate, and its oligosaccharides on peeled shrimp (Litopenaeus vannamei) during frozen storage was investigated by monitoring thawing loss, color, texture, myofibrillar protein content, Ca²⁺‐ATPase activity, and performing microscopic structural analysis. Data revealed significant (p < 0.05) inhibitory effects on thawing loss and textural variables (springiness and chewiness) in trehalose‐, alginate oligosaccharides‐, and sodium pyrophosphate‐treated shrimp compared with the control and alginate‐treated batches. L* values revealed that these saccharides had a positive effect on color stability during frozen storage. In addition, the results of chemical analyses showed that trehalose and alginate oligosaccharide treatments effectively maintained an increased myofibrillar protein content and Ca²⁺‐ATPase activity in frozen shrimp. In addition, hematoxylin & eosin staining and SDS‐PAGE confirmed that these cryoprotective saccharides slowed the degradation of muscle proteins and the damage to muscle tissue structures. Overall, the application of trehalose and alginate oligosaccharides to peeled frozen shrimp might maintain better quality and extend the commercialization of these refrigerated products.     

控制腊肠脂肪酸败的研究

本文针对腊肠在贮藏过程中的脂肪氧化酸败问题,运用综合控制措施加以解决.结果表明添加AO3抗氧化剂后,腊肠在30℃、65%RH和1520℃、3040%RH条件下贮藏时均能显著延缓腊肠酸败的发生.同时发现新包装材料结合使用脱氧剂对控制腊肠的脂肪氧化也有明显效果.     

Effect of Chitosan Coatings Enriched with Lauroyl Arginate Ethyl and Montmorillonite on Microbial Growth and Quality Maintenance of Minimally Processed Table Grapes (<Emphasis Type="Italic">Vitis vinifera</Emphasis> L. Kyoho) During Cold Storage

The effects of lauroyl arginate ethyl (LAE), chitosan (CTS), and CTS-containing montmorillonite and LAE coatings (CML) on the quality maintenance and shelf life of minimally processed grapes stored at 4 °C for 20 days were investigated. Compared with the control, LAE, and pure CTS coatings, the CML coatings effectively decreased grape weight loss, respiration, and decay incidence as well as microorganism counts of total aerobic bacteria, yeasts, molds, and lactic acid bacteria in grapes. The CML coatings also showed better effects on delaying the tissue softening and browning due to the decreased activities of polygalacturonase, pectin methyl esterase, and polyphenol oxidase. CML coatings did not significantly change the content of soluble solids and the titratable acidity or the pH value of grapes, compared with other samples. However, CML coatings ensured higher content of ascorbic acid and sensory quality in grapes. The results confirmed that CML coatings improve microbiological safety and preserve nutritional and sensory quality of minimally processed grapes.