桃品质的无损检测技术研究进展

桃果实营养物质丰富,是消费者青睐的水果之一。但桃在生长、采摘和贮藏过程中易受到损害而导致品质下降,严重影响桃的经济价值,因此桃品质检测技术对于保障果实商业价值具有至关重要的作用。传统的检测方法具有耗时长、成本高、对样品有破坏性等缺点,而基于声学特性、力学特性、介电特性、光学特性和电子鼻的无损检测方法,特别是基于光学特性的检测方法,因其无损、快速、准确的优势而发展迅速,目前在桃果实内外部品质检测中得到广泛的应用,然而目前对其优缺点及今后的发展方向缺乏系统总结。本文综述应用上述无损检测技术,尤其是基于光学特性和电子鼻的无损检测方法,评估桃果实外部品质（大小、形状、色泽、香气、表面缺陷）和内部品质（品种、糖度、可滴定酸含量、硬度、冷害、虫害等）的最新研究进展,总结分析了其在桃品质检测中存在的问题,并对桃品质无损检测研究方向进行展望,以期为桃品质无损检测技术的研究提供参考。     

Determinants of seafood consumption in Norway: lifestyle,revealed preferences,and barriers to consumption

Little research attention has previously been paid to understand the complementary relationship between the consumption of seafood and variation in lifestyle factors. The present paper seeks to address this question by hypothesizing that the consumption of seafood is strongly influenced both by the variation in lifestyle factors and consumer's experience with available products in the market. Understanding the main lifestyle factors influencing consumption behaviour and seafood demand is important for marketers who want to increase the product values both for the consumers and themselves. A recursive sequential model of the decision-making process is used to evaluate the effect of socio-demographic variables, consumption of other dinner dishes, other lifestyle variables, and attitudes towards seafood on consumption amongst women of three major seafood categories at-home. The most important finding which can be influenced through the marketing process is that product attributes more than beliefs concerning price are important perceived barriers for consumption. The presence of school-aged kids in the household and regional residence influences what kind of seafood is consumed, while total consumption increases with increasing size of the household, increasing age and higher education. This indicates that there is a potential for suppliers to increase the sales value through marketing of high quality products which satisfy experienced and higher educated consumers, while families with kids should be satisfied through marketing of value-added product forms.     

Relationship of Quality Characteristics of Peaches (cv. Loring) to Maturity

The effect of maturity and ripening on the quality characteristics of Loring peaches was determined. Size, weight, Minolta a values, sucrose, total sugar, soluble solids (SS) and SS/TA ratio of cv. Loring peaches increased significantly with increased degree of maturity of fruit. Firmness, titratable acidity (TA) and delayed light emission (DLE) decreased significantly with increased maturity grade. The fruit of grades 1 and 2 did not attain sensory characteristics similar to tree ripe fruit (grades 6 and 7). The fruit of those grades were less sweet and more sour than grades 3-7. The optimum maturity for harvesting Loring peaches for optimum quality was maturity grade 5.     

CONSUMER PERCEPTIONS OF QUALITY: APRICOTS, CANTALOUPES, PEACHES, PEARS, STRAWBERRIES, AND TOMATOES

Consumers are increasing their produce consumption; however, complaints of inconsistent produce quality and improper consumer handling practices could reduce consumer satisfaction with and demand for specific produce items. Seventy to eighty percent of consumers buy cantaloupes, peaches, pears, strawberries and tomatoes at the supermarket; only about half buy apricots at the supermarket. Apricots are not purchased at any location by almost 30% of consumers. Satisfaction with quality is highest for cantaloupes, lowest for tomatoes and apricots. Consumer complaints center around flavor and textural changes which develop in ripening. Both consumer handling practices and fresh product quality contribute to dissatisfaction.     

SHORT‐TERM CONTROLLED ATMOSPHERE STORAGE FOR STORAGE‐LIFE EXTENSION OF WHITE‐FLESHED PEACHES AND NECTARINES1

Abstract Response of white‐fleshed peaches (‘Sugar Lady’, ‘Snow Giant’, ‘White Lady’and ‘Snow King’) and nectarines (‘Arctic Queen’and ‘Arctic Rose’) to controlled‐atmosphere (CA) storage is cultivar dependent. Samples of fruit of these six cultivars were collected just prior to commercial harvest and held in either regular‐atmosphere (RA) storage at 1C or controlled‐atmosphere (CA) storage at 2% O₂ and 6, 12 or 18% CO₂, all at 1C. Four of the six cultivars (‘Snow Giant’, ‘White Lady’, ‘Snow King’and ‘Arctic Queen’) displayed excessive internal browning and poor flesh color after only 30 days of storage and should not be considered for long storage (+30 days). While ‘Sugar Lady’and ‘Arctic Rose’performed better and are possible candidates for CA storage, they should not be stored more than 45 days after harvest. The value of CA storage to extend the marketing of white‐fleshed peaches and nectarines is questionable at best. If CA storage is to be used for storage‐life extension of white‐fleshed peaches and nectarines, O₂ level should be maintained at 2% or less and CO₂ level maintained at 12% or higher.     

What’s the deal? Consumer price involvement and the intention to purchase suboptimal foods. A cross-national study

Retailers aim to supply consumers exclusively with food products that are flawless, and therefore impose strict standards that foods have to comply with before deemed qualified for retail. This practice results in large amounts of foods, suitable for human consumption, to be discarded due to deviation from these standards. In an effort to battle food waste, retailers have begun to offer suboptimal food products on price promotion. However, consumers’ reactions to price promotions are not uniform and depend on the significance individuals assign to these promotions, based on their own price involvement. An online questionnaire administered to a total sample of 3,114 consumers divided across representative samples of Dutch (n = 628), German (n = 622), Swedish (n = 620), Norwegian (n = 625) and Danish (n = 619) consumers aimed to investigate the effect of five price involvement dimensions (Deal proneness, Value consciousness, Price consciousness, Price-Quality schema, Prestige sensitivity), Perceived budget constraints, and current use of suboptimal foods on consumers’ intention to purchase these products in the near future. Results indicate that consumers’ intention to purchase suboptimal foods is influenced by different price involvement dimensions within and across countries. These findings offer evidence that a more nuanced approach to price promotions can increase consumers’ intentions to purchase suboptimal foods and thus prove an efficient marketing tool that can be used to help reduce food waste. Retailers could benefit from applying price promotions that tap into the price involvement dimensions that increase consumers’ intentions to purchase suboptimal foods, in contrast to the current practice of applying uniform price reductions.     

IRRADIATION AS AN ALTERNATIVE TO METHYL BROMIDE FOR QUARANTINE TREATMENT OF STONE FRUITS1

Irradiation can be used with cherries, apricots, or peaches as a quarantine treatment at 300gy's or less with little quality loss. Either irradiation or methyl bromide (MeBr) can be used as a quarantine treatment for ‘Bing’‘and ‘Rainier’ sweet cherries with acceptable results and similar fruit quality. Difference in stem condition and bruising were more evident for irradiated ‘Rainier’ cherries than for MeBr treated ‘Rainier’ cherries, but these differences were small. Use of irradiation results in some firmness loss, for ‘Bing’ cherries when compared with MeBr, but irradiation treatment of cherries does not result in a loss of fruit and stem color, where the use of MeBr doses result in both fruit and stem color loss. Apricots (‘Perfection’ and ‘Rival’) and peaches (‘Regina’) are tolerant to irradiation at 300 gy with little quality loss. Loss of firmness, color changes and increased internal breakdown are evident in both apricots and peaches at irradiation dose above 600 gy. If irradiation dose above 600 gy is required to meet quarantine requirements unacceptable qualidy loss will occur in cherries, apricots and peaches.     

Synergistic mechanism of steam blanching and freezing conditions on the texture of frozen yellow peaches based on macroscopic and microscopic properties

Freezing and blanching are essential processing steps in the production of frozen yellow peaches, inevitably leading to texture softening of the fruit. In this study, the synergistic mechanism of stem blanching, freezing conditions (−20°C, −40°C, −80°C, and liquid nitrogen [−173°C]), and sample sizes (cubes, slices, and half peaches) on macroscopic properties of texture, cellular structure, and ice crystal size distribution of frozen yellow peaches were measured. Blanching enhanced the heat and mass transfer rates in the subsequent freezing process. For nonblanched samples, cell membrane integrity was lost at any freezing rate, causing a significant reduction in textural quality. Slow freezing further exacerbated the texture softening, while the ultra-rapid freezing caused structural rupture. For blanched samples, the half peaches softened the most. The water holding capacity and fracture stress were not significantly affected by changes in freezing rate, although the ice crystal size distribution was more susceptible to the freezing rate. Peach cubes that had undergone blanching and rapid freezing (−80°C) experienced 4% less drip loss than nonblanched samples. However, blanching softened yellow peaches more than any freezing conditions. The implementation of uniform and shorter duration blanching, along with rapid freezing, has been proven to be more effective in preserving the texture of frozen yellow peaches. Optimization of the blanching process may be more important than increasing the freezing rate to improve the textural quality of frozen yellow peaches.     

Isolation, Identification and Comparison of the Volatiles of Peach Fruit as Related to Harvest Maturity and Artificial Ripening

SUMMARY: Volatiles of peach (Prunus persica L., cultivar, Gleason Early Elberta) fruit were studied by gas-liquid chromatography, thin-layer chromatography and infrared spectrometry. Chromatograms of the volatiles of hard-mature, firm-mature, soft-mature, tree-ripe and artificially ripened, hard-mature fruit were obtained with temperature programing and flame ionization detection. The volatile concentrates of tree-ripe peaches produced 86 peaks. The major peaks were isolated and the infrared spectra determined and compared with authentic compounds.
In general, concentrations of volatile components increased with advancing maturity. The main volatile components were identified as gamma- and delta-lactones, esters, aldehydes, benzyl alcohol and d-limonene.
The highest total lactone concentration occurred in tree-ripe peaches and was more than four times that of firm-mature fruit. Gamma-decalactone predominated among the lactones in tree-ripe peaches. Artificially ripened peaches had very small amounts of gamma-decalactone and lacked gamma- and delta-dodecalactone, with a total lactone concentration abouf one-fifth that of free-ripe fruit. Concentrations of esters in artificially ripened fruit reached only one-third to one-half those of tree-ripe peaches. Benzaldehyde was the predominant volatile in tree-ripe peaches and occurred in five times the concentration found in artificially ripened fruit. These may be the determining factors relative to the inferiority of artificially ripened as compared to free-ripened fruits.     

PRODUCT DEVELOPMENT AND NUTRACEUTICAL ANALYSIS TO ENHANCE THE VALUE OF DRIED FRUIT

ABSTRACT

Value‐added fruit products suitable for production by small‐scale farmers and processors were developed and evaluated. Apples, blueberries, peaches and strawberries from local growers were processed into a dried fruit product. The total phenolics, total anthocyanins and oxygen radical absorbing capacity (ORAC) were determined. Drying the fruit concentrated total phenolics, total anthocyanins and ORAC levels as compared to fresh fruit. The nutraceutical components of the blueberries, peaches and strawberries of the local dried fruit were higher than those of commercial dried fruit purchased at a natural food store. The dried fruit from both the local and commercial fruits was used to create a fruit pie filling for consumer evaluation. Consumer acceptance of fruit pie filling from dried fruit grown locally and dried commercial fruits was evaluated using a 9‐point verbal hedonic scale and a 5‐point Just About Right scale. In terms of consumer evaluation, the pie fillings made from local dried fruits were either better or at parity with those from commercial products. In addition to the nutraceutical benefits, the pie fillings were consumer acceptable products that could represent an avenue for small‐scale farmers to add value to surplus fruit.

PRACTICAL APPLICATIONS

Complete utilization of fruit crops is a key component to the success of small farm operations. Excess fruit crops can be dried (or processed in other manners) and used to create many value‐added products. Increased consumer awareness of healthy food products provides a niche market for these fruit products. In this research, the nutraceutical benefits of fresh and dried apples, blueberries, peaches and strawberries were investigated and the consumer overall acceptance of a pie filling produced from these dried fruit was shown.

     

桃的介电特性和品质关系

以‘秦光2号’油桃为研究对象,对果实的电特性进行研究,同时测定果实的品质指标。结果表明：在测试电频率1MHz条件下,油桃果实的复阻抗(Z)、并联等效电感(Lp)、硬度、可溶性固形物、可滴定酸含量和含水率在室温(25℃)条件下随着贮藏时间的延长不断降低,而并联等效电容(Cp)不断上升。‘秦光2号’油桃果实的电参数(Z、Cp、Lp)和品质参数(硬度、可溶性固形物、可滴定酸和含水率)之间的相关性达到显著水平(P＜0.05,P＜0.01),对其建立了有效的预测模型(相关系数都达到显著水平),表明可采用介电参数反映桃果实的品质特性。     

Animal Welfare Labelling and the Approach of the European Union: An Overview on the Current Situation

There is a growing appreciation of the insistence of consumers that animals used in food production should be well treated. High welfare standards could have both a direct and indirect impact on food safety and quality; regulatory and support systems in agriculture must adapt accordingly. Retailers and producers are increasingly recognising animal welfare as a fundamental aspect of product image and quality which create a need for reliable systems for on farm monitoring of animal welfare status and providing some warranty on appropriate production conditions. The article shows an overview of the European strategies for implementing the animal welfare labelling. Received: July 2, 2008; accepted: July 8, 2008     

MODIFIED ATMOSPHERE STORAGE OF PEACHES AND NECTARINES TO REDUCE STORAGE DISORDERS1

Low density polyethylene or polyolefin films were used to seal pack various varieties of peaches and nectarines. Low density polyethylene film of 40 micron thickness was beneficial in extending storage life of these fruits and decreasing internal flesh breakdown and reddening, while polyolefin film was ineffective. Six fruits per pack generated a higher CO₂ and lower O₂ modified atmosphere than two or four fruits per pack and gave better quality fruit after storage. The improvement of fruit quality was correlated with elevated CO₂ levels rather than with decreased O₂ levels.     

Preconditioning treatment maintains taste characteristic perception of ripe ‘September Sun’ peach following cold storage

Preconditioning is a thermal treatment that consists in maintaining stone fruits immediately after harvest and prior to cold storage at 20 °C for 24–48 h in special chambers aimed to extend fruit market life reducing chilling injury symptoms. This work investigates whether preconditioned ‘September Sun’ peaches had better eating quality than control fruit. Commercially harvested peaches were preconditioned and transferred to cold storage for 12, 26 and 40 days and evaluated for sensory characteristic perception after a ripening period at 20 °C. Acceptability of preconditioned fruit was higher than control fruit during this 40‐day cold‐storage period. Preconditioned and control fruit were also segregated into two clusters by PCA analysis; preconditioned fruit clustered together and show association to acceptability, sweetness and juiciness, while the second cluster was associated with flesh texture, acidity and aroma, suggesting the positive effect of preconditioning on final fruit quality. Preconditioned fruit maintained their sensory characteristics longer than control fruit during this 40‐day cold‐storage period.     

SENSORY AND OBJECTIVE MEASUREMENTS OF PEACH FIRMNESS

A non-destructive random-vibration technique was used to test whole intact peaches over the frequency region 250–10000 Hz. Changes in the vibration properties of peaches during maturation and ripening were related to changes in fruit firmness. Vibration measurements in the frequency region 2–5 kHz provided the best correlations with pressure test measurements and with sensory firmness ratings. Such correlations were in general greater than 0.80.     

Low‐temperature conditioning combined with methyl jasmonate treatment reduces chilling injury of peach fruit

BACKGROUND: Peaches are sensitive to low temperature and develop chilling injury (CI) symptoms during refrigerated storage. This CI reduces consumer acceptance of peaches and limits the potential postharvest market life of the fruit. To develop a suitable technique to reduce CI, the effect of a combination of low‐temperature conditioning (LTC) and methyl jasmonate (MJ) treatment on CI of peach fruit was investigated in this study. RESULTS: Freshly harvested firm‐mature peaches were treated with a combination of LTC at 10 or 20 °C and 1 µmol L^?1 MJ and then stored at 0 °C for 5 weeks. The fruits developed CI during storage, manifested as internal browning and flesh mealiness. The combined treatment significantly reduced these CI symptoms and maintained higher fruit quality. The activities of polyphenol oxidase and peroxidase were significantly inhibited while those of superoxide dismutase, catalase and ascorbate peroxidase were induced by the combined treatment. In addition, the activities of phenylalanine ammonia‐lyase and polygalacturonase and the level of total phenolics were enhanced by the combined treatment. CONCLUSION: The combination of LTC and MJ treatment could be a useful technique to reduce CI and maintain quality in peach fruit during cold storage. Copyright © 2009 Society of Chemical Industry     

DEVELOPMENT OF POLYGALACTURONASE ACTIVITY AND SOLUBILIZATION OF PECTIN IN PEACHES DURING RIPENING

SUMMARY –Polygalacturonase activity, water-soluble pectin, total pectin, molecular weight distribution of water-soluble pectin, and fruit firmness were determined during ripening of freestone peaches. Polygalacturonase activity was not present in unripe peaches, but it developed during both tree and postharvest ripening. The development of activity paralleled the formation of water-soluble pectin characteristic of freestone peaches. Fruit firmness began to decrease before polygalac-turonase was detected, but the peaches softened rapidly after the appearance of the enzyme. Application of gel filtration revealed that the molecular weights of peach pectin range from about 100,000 to several million and decrease progressively during ripening. The results indicate a role for polygalacturonase in pectin solubilization during ripening of peaches.     

Quality, bioactive compounds, and antioxidant activity of new flat-type peach and nectarine cultivars: a comparative study

In this work, some organoleptic and nutritive parameters related to fruit quality (color, firmness, total soluble solids, and total acidity), the content of bioactive compounds (total phenolics and total carotenoids) as well as the total antioxidant activity (TAA) due to hydrophilic (H-TAA) and lipophilic (L-TAA) compounds have been determined in both skin and flesh of 10 flat peach and nectarine genotypes (7 peaches and 3 nectarines). Results showed that genotype plays an important role in determining the organoleptic and nutritive quality, as well as the concentration of bioactive compounds and the related TAA, since these parameters differed largely among cultivars. Overall data suggest that for commercial purposes and consumer's acceptability (based on color, firmness, acidity, and bioactive compounds), the flat nectarine "ASF-06-83" and the flat peaches "Sweet Cap" and "ASF-06-91" could be considered as the best cultivars. Additionally, it is suggested that the content of bioactive compounds should be included as an important factor in future breeding program to obtain new genotypes with enhanced bioactive compounds. PRACTICAL APPLICATION: Genotype of flat peaches and nectarines plays an important role in determining the organoleptic and nutritive quality, as well as the content of bioactive compounds. Given the differences on bioactive compounds concentration and antioxidant activity among peaches and nectarines flat cultivars, these parameters should be included as an important factor in future breeding program to obtain new genotypes with enhanced bioactive compounds.     

DISCOLORATION OF SUN-DRIED AND PROCESSED ELBERTA PEACHES DURING STORAGE

Discoloration of sun-dried 'Elberta' (Prunus persica) peaches during a 48 week storage period as affected by moisture content (15 and 17%) and temperature (4, 7, 10 and 20C) was investigated. In addition, the effect of rehydration to moisture contents of 20, 24 and 27% and resulphuring on the color of the processed fruit during storage for 100 days at 0 and 25C was studied. Drying fruit to 15% instead of 17% moisture content gave darker-colored fruit, and it did not improve color retention during storage. Storage at 20C decreased L* values, indicating darkening of the fruit, but the quality, correlated with chroma, was still acceptable for fruit obtained with most of the treatment combinations. Substantial losses of SO₂ occurred at 20C. Rehydration and resulphuring increased chroma and hue values of the fruit. Storage of processed fruit at OC was effective in preventing discoloration, irrespective of treatment, while discoloration took place at 25C.