Pear peeling using infrared radiation heating technology

Infrared radiation (IR) heating could be a potential alternative peeling method to address the long-term water supply and wastewater disposal issues involved in the conventional lye peeling process of pears. The objective of this study was to investigate the feasibility of IR peeling technology as an environmentally friendly alternative practice to efficiently produce peeled pear products with superior quality and yield. A pilot IR Dry-Peeling System consisting of catalytic IR emitters, roller conveyor, and peeler remover was developed and used for this research. Effects of the pear firmness and heating time on the peeling performance and product quality were studied. Under the continuous loading condition, the most desirable peeling result was achieved for Bartlett pears in the initial firmness range of 22 to 31 N after 99 s of IR heating. The results of IR peeling indicated superior product quality with relative thin cooking ring (0.76 ± 0.20 mm), limited peeling loss (9.25 ± 1.25%), and fairly ease of peeling (5.33 ± 1.00). According to SEM photomicrographs of pericarp cross-section, IR heating caused loss of integrity and compartmentalization of cells of the hypodermal layer to only “ripe” pears (firmness of 26.5 ± 2.8 N). Thermal effect of IR heating dramatically disrupted the middle lamella of hypodermal cells and resulted in mechanical failure of those cells and subsequent layer loosening of “ripe” pears.     

Moisture diffusivity of rough rice under infrared radiation drying

To design efficient infrared (IR) dryers for rough rice, it is important to understand the drying behavior of rough rice under IR heating. The objective of this study was to determine the moisture diffusivity of rough rice under IR heating followed by cooling. The effects of initial moisture content, rice temperature, drying bed thickness, tempering, and cooling methods on moisture diffusivity and moisture diffusivity coefficient were investigated. Samples of freshly harvested medium grain rice (M202 variety) with initial moisture content (MC) of 25.8, 31.2 and 33.8 g moisture/100 g dry solid were used. They were dried with IR radiation intensity of 5348 W/m², for six exposure times, 15, 30, 40, 60, 90 and 120 s. The tested drying bed thicknesses were single-layer, 5 mm and 10 mm. The unsteady diffusion equation based on Fick’s law and slope methods were used to describe moisture diffusivity. The results indicated that rough rice moisture diffusivities under IR heating and cooling were significantly affected by rice temperature and tempering treatment, respectively. High heating rate and moisture diffusivity were achieved with IR heating. It took only 60, 90 and 120 s to achieve about 60 °C rice temperature with corresponding moisture diffusivities of 4.8 × 10⁻⁹, 3.6 × 10 ⁻⁹ and 3.4 × 10⁻⁹ m²/s during heating for drying bed thicknesses of a single layer, 5 mm and 10 mm, respectively. The moisture diffusivity coefficients during heating and cooling of IR dried rice with tempering were much higher than those of convective drying, which reflected the high drying rate of the IR drying method.     

Microwave-assisted infrared dry-peeling of beetroot: Peeling performance,product quality,and cell integrity

The use of low power-short time microwave (MW) treatment before infrared (IR) heating could help improve the peeling performance of beetroot. MW-assisted IR peeling (MWIR) and IR peeling of beetroot were investigated and compared with the conventional hot-lye peeling method. Also, the effects of these peeling methods on the quality and microstructure were evaluated. Hot-lye peeling at 95 °C for 40 s and 60 s was used as control. Results showed that MW-assisted IR peeling at power 640 W and heating time 7 min produced samples with the highest peelability (99.4%), lowest peel thickness (0.075 mm), and peel remaining (0.8%), lower peeling loss (4.23 g), and better peeling easiness when compared with lye peeling and IR peeling. IR peeling alone produced samples with the lowest peeling loss (2.87 g) and surface colour change, and the highest vitamin C retention (75.32%) than MW-assisted IR and lye peeling respectively. The product microstructure for the different peeling methods showed cellular distortion as a result of thermal expansion. MW pretreatment shows a promising potential to further develop the IR dry-peeling method, to replace the conventional hot lye chemical peeling.     

AN EXPERIMENTAL DRY CAUSTIC PEELER FOR CLING PEACHES AND OTHER FRUITS

SUMMARY– An experimental cling peach peeler was developed for continuous removal of alkaline peel as a solid rather than the dilute slurry of common industrial practice. The peeler consists of rows of soft rubber disks rotated in such a manner that peel material is gently wiped from the surface of fruit and flung into collectors. Cling peach halves were successfully peeled in a number of tests, with peeling losses comparable to those normally obtained commercially. Both mature and immature Bartlett pears were also successfully peeled. Dewaxing of immature pears with isopropy¹ alcohol was necessary to obtain adequate peeling. In single tests, whole apricots and freestone peaches were also successfully peeled.     

Application of a mathematical model for chemical peeling of peaches (Prunus persica l.) variety Amarillo Jarillo

A previous model developed by the authors for chemical peeling of spherical foods was applied to peaches, which were assimilated to that geometry. Equations for the prediction of chemical peeling time as a function of temperature; alkali concentration and peeled thickness; and texture changes due to the cooking effect during peeling were established. Likewise, weight loss associated to peeling was determined. A total of 128 experiments were performed, involving caustic soda concentration of 1.6, 3.2, 5.6 and 7.3 (g/100 ml) and temperatures of 70, 80, 90 and 97 °C for peeling times from 0 to 8 min at 1-min intervals. Peeling maps to estimate peeling time for practical peeling conditions, including alkali temperature (70-97 °C), alkali concentration (1.6-7.3 g/100 ml), and peel thickness (0.02-0.05 cm) were developed.     

High-humidity hot air impingement blanching (HHAIB): An emerging technology for tomato peeling

Peeling is an essential operation for tomato processing. A new peeling method, high-humidity hot air impingement blanching (HHAIB) heating technology, was developed as an alternative to the conventional lye and hot-water peeling to eliminate the use of chemicals and the discharge of wastewater. The current work explored the feasibility of HHAIB for tomato peeling. The effects of heating temperature (100–120 °C), relative humidity (20%–40%) and heating time (0–180 s) on the peeling performance were investigated. The optimum treatment was found to be 110 °C heating temperature in combination with 40% of relative humidity and 75 s treatment time, which resulted in lower peeling loss, firmness loss and color deterioration compared with other HHAIB conditions that achieved 100% peelability. The comparative study of optimized HHAIB peeling with conventional lye and hot-water peeling showed that HHAIB peeled tomato obtained lower peeling loss and firmness loss, and higher preservation of phytochemicals, antioxidant capacity and color. In addition, compared with fresh tomatoes, HHAIB processing increased the antioxidant activity, lycopene, and total phenolic content in peeled tomatoes by 16.01%, 10.46%, 12.80%, respectively. The laser scanning confocal microscopy image of fresh tomato skin surface and the scanning electron microscope images of peels and flesh showed that HHAIB caused cracking of the epidermis and melting of the cuticular membrane while reduced the serious damage of flesh.Industrial practicePeeling is a necessary step in tomato processing, which impacts subsequent processing efficiency and product quality. At present, the most common used peeling methods in the industry are hot water or/and alkali peeling, but it induces the loss of water-soluble nutrients, chemical residues and waste liquid treatment. Therefore, the industry urgently needs an alternative peeling technology. The current work shows that HHAIB is a very promising peeling technology as it not only has an excellent peeling performance, but also enhances the preservation of phytochemicals, antioxidant capacity and quality attributes compared to conventional lye and hot-water peeling.     

Kinetics of salmon quality changes during thermal processing

The kinetics of reactions leading to changes in salmon quality during thermal processing were evaluated. Small samples (D 30 mm × H 6 mm) cut from pink salmon (Oncorhynchus gorbuscha) fillets were sealed in aluminum containers (internal dimension: D 35 mm × H 6 mm) and heated in an oil bath at 100, 111.1, 121.1, and 131.1 °C for different time intervals up to 180, 150, 120, 90 min, respectively. A fractional conversion model was used to describe the increase in cook loss during heating; and a quadratic relationship to correlate cook loss with area shrinkage ratio. Color changes (CIE L¹, b¹ and ΔE) involved whitening and browning phases. In the browning phase, the changes of CIE L¹, b¹ and ΔE followed a zero-order reaction. The progressive change of texture with time as indicated by shear force during heating went through four different phases, and the second (rapid tenderizing) and third phases (slow toughening) were modeled using a first-order reaction kinetic model. The decay of thiamin during heating was modeled with two different relationships: a second-order reaction in which the temperature dependence of the rate constant followed an Arrhenius relationship; and a Weibull-log logistic model recently proposed.     

Alternative Method for Hazelnuts Peeling

The paper proposes an improved peeling treatment for hazelnut fruits consisting in dipping them in a solution (NaOH 0.4 g/100 g, NaH₂PO₄·H₂O 0.2 g/100 g) for 10 min at 50 °C, then scrubbing them with rubber rollers. The effects of the treatment on quality and peeling of four Italian hazelnut varieties were investigated. The data collected on peeling capability showed that the treatment proposed was effective in cuticle removal with a yield of peeling higher than 90%. The comparison of chemical–physical parameters in unpeeled and peeled hazelnut samples highlights that no difference was detected in texture, sugar, protein and α-tocopherol values. After the peeling process a significant change (p < 0.05) in colour, total fat and peroxide value was observed in peeled hazelnut samples when compared with the unpeeled ones. With regard to the sensorial parameters, no significant changes were found between unpeeled and peeled hazelnut samples. The peeling solution proposed in this study shows a good potential in industrial applications as an alternative to the usual manufacturing peeling method (roasting) that causes changes, not always desired, to some sensorial and chemical–physical parameters of the fresh fruit.     

Monitoring of firmness evolution of peaches during storage by combining acoustic and impact methods

Firmness is a very important quality property in peach. The storage of peach affects its subsequent softening process and shelf life. The temperature and duration of storage mainly influence the firmness of stored fruit, and monitoring the evolution of fruits enables producers to manage its commercial life. The objective of the present study was to use non-destructive acoustic and impact tests to estimate firmness of peaches and to elucidate the influence of storage temperature and of time on the softening process of peach. Continuous and classification models based on variables obtained from non-destructive methods were developed. Parameters obtained from non-destructive methods were compared to destructive reference tests. The maximum force in ball compression correlated well with the maximum acceleration from impact test (r² = 0.75), and with a band magnitude parameter from acoustic test (r² = −0.71). Combining impact and acoustic parameters, the multiple correlation coefficient increases up to 0.91 (adjusted R² = 0.82) in the prediction of the maximum force in ball compression. Classification models based on both non-destructive parameters and sorting peaches into two classes of firmness, showed scores of well classified higher than 90%.     

Nutmeg's (Myristica Fragrans Houtt) Oleoresin: Effect of Heating to Chemical Compositions and Antifungal Properties

The aim of the study was to evaluate the effect of heating on the chemical compositions and antifungal properties of nutmeg's oleoresin. Nutmeg's oleoresin was obtained by two steps, distillation followed by maceration. The nutmeg's oleoresin was heated at 100^oC, 120^oC and 180^oC. The chemical compositions were determined by GC-MS, and the antifungal properties by giant colony method. The result of the study showed that yield was 13.6%±0.2% and 24 components were identified. The nutmeg's oleoresin at 100 °C, 120 °C and 180 °C identified 25, 21 and 20 components. Indeed, heating treatment on nutmeg's oleoresin did not decrease the antifungal properties.     

Effect of peeling and unpeeling on yield,chemical structure,morphology and pasting properties of starch extracted from three diverse potato cultivars of Pakistan

The current study investigates the comparison and quality characteristics of starches isolated from potatoes using different processing methods from three commercial varieties: Lady Rosetta, Asterix and Challenger, for the first time in Pakistan. The analysis of variance revealed that starch yield significantly (P < 0.05) depended on total solids, peeling (12.7%, 12.0% and 12.0%) and unpeeling (15.0%, 14.0% and 14.0%) of potatoes compared to potato varieties for Lady Rosetta, Challenger and Asterix, respectively. Moreover, pasting properties, protein content, redness and yellowness were increased in those starches isolated without peeling while carbohydrates and lightness were increased in peeled potato starches. Furthermore, Fourier-transform infrared spectroscopy analysis revealed that protein (1200–1400 cm⁻¹) was present in starch extracted without peeling. Besides, scanning electron microscopy analysis revealed oval-shaped starch granules with no impurities in peeled potato starch. The findings suggest the suitability of peeling process for obtaining a high-quality pure starch.     

Stability of black carrot anthocyanins in various fruit juices and nectars

Fruit juices (apple, grape, orange, grapefruit, tangerine and lemon) and nectars (apricot, peach and pineapple) were coloured with black carrot juice concentrate and stability of black carrot anthocyanins in these matrices was studied during heating at 70–90 °C and storage at 4–37 °C. Anthocyanin degradation, in all coloured juices and nectars, followed first-order reaction kinetics. During heating, black carrot anthocyanins in apple and grape juices showed higher stability than those in citrus juices at 70 and 80 °C. High stability was also obtained for the anthocyanins in peach and apricot nectars at these temperatures. Black carrot anthocyanins were the least stable in orange juice during both heating and storage. During storage, degradation of anthocyanins was very fast at 37 °C, especially in pineapple nectar. Refrigerated storage (4 °C) markedly increased the stability in all samples. Activation energies for the degradation of black carrot anthocyanins in coloured juices and nectars ranged from 42.1 to 75.8 kJ mol⁻¹ at 70–90 °C and 65.9–94.7 kJ mol⁻¹ at 4–37 °C.     

Gelation characteristics of tropical surimi under water bath and ohmic heating

Gelation characteristics of tropical surimi, namely threadfin bream (TB), bigeye snapper (BS), goatfish (GF) and lizardfish (LF) prepared in the absence and presence of 10 g kg^?1 egg white proteins were evaluated using either ohmic (OH) or water bath (WB) heating. LF and GF surimi exhibited higher endogenous proteolytic activity than BS and TB. Ohmic heating markedly minimized proteolysis of LF and GF surimi as evidenced by a reduction of trichloroacetic acid (TCA)-soluble oligopeptide content of gels and more retention of myosin heavy chain (MHC). Ohmic heating increased breaking force and deformation of TB and BS surimi by 1.3 and 1.6 times, respectively, as compared to water bath heating. However, TB surimi gels heated by a higher applied voltage gradient of 16.7 V cm^?1 exhibited lower breaking force than those heated at 6.7 V cm^?1. Gels heated ohmically contained lower total sulfhydryl concentration, indicating the greater extent of disulfide bond formation as compared to gels heated in a 90 °C water bath. The rapid heating method with shorter heating time could improve water holding capacity and preserve color of tropical surimi gels when compared to water bath heating.     

桃加工过程中3种噻二唑类农药残留动态

目的 研究清洗和去皮对桃中噻唑锌、噻菌铜和噻森铜残留的影响及榨汁和罐头加工过程中3种农药的残留变化规律。方法 采用室内模拟桃加工方式, 通过高效液相色谱-串联质谱法(high performance liquid chromatography-tandem mass spectrometry, HPLC-MS/MS)检测噻唑锌、噻菌铜和噻森铜在桃中的残留。结果 清洗和去皮对降低桃中噻唑锌、噻菌铜和噻森铜的残留效果显著, 清洗对3种农药的去除率分别为62%、60%和83%, 去皮对3种农药的去除率分别为80%、64%和91%。榨汁后, 噻唑锌、噻菌铜和噻森铜在果汁中的转移率分别为17%、18%和24%, 在果渣中的转移率分别为63%、58%和54%。罐头加工过程中, KMnO4消毒和去皮对3种农药残留去除率较高, 分别为58%~65%和30%~75%; 漂烫和加入糖水对3种农药的去除率较低, 分别为5%~13%和8%~19%。桃果汁和罐头加工后3种农药的加工因子小于1, 桃果渣加工后3种农药的加工因子大于1。结论 清洗和去皮可大量减少桃中噻唑锌、噻菌铜和噻森铜残留, 桃果汁和罐头加工使3种农药残留水平降低, 果渣加工使三种农药残留水平升高。此研究可为桃饮品和桃罐头的膳食风险评估以及加工过程中农药残留消减提供数据参考。     

Use of propidium monoazide and quantitative PCR for differentiation of viable Escherichia coli from E. coli killed by mild or pasteurizing heat treatments

Suspensions of Escherichia coli in peptone water were heated at temperatures between 52 and 90 °C, inclusive. Samples withdrawn at suitable times were not or were treated with propidium monoazide (PMA) or deoxycholate then PMA before extraction of DNA. DNA was quantified by real-time PCR for estimation of the numbers of E. coli from which template DNA for the PCR was obtained. Numbers of viable E. coli in suspensions at the times of sampling were determined from plate counts. For samples from suspensions heated at temperatures ≥52 ≤ 72 °C, PCR cycle threshold (Ct) values were little or no different for DNA from corresponding samples that were or were not treated with PMA. PMA treatment of samples heated to ≥80 °C largely inactivated E. coli DNA for PCR. When samples heated to ≤72 °C were treated with deoxycholate before treatment with PMA, Ct values for treated samples were greater than the Ct values for the corresponding untreated samples. Similar results were obtained with E. coli suspended in milk or fluid from ground beef pummeled with diluent. The results indicate that cells killed by heating to ≥80 °C are permeable to PMA, but most cells killed by heating to ≤72 °C are not. However, treatment with deoxycholate renders a substantial fraction of the latter cells permeable to PMA. Numbers of viable or dead E. coli can then be estimated from Ct values for samples not treated or treated with deoxycholate and PMA, provided viable cells are ≥1% of the total.     

Radio frequency heating as a disinfestation method against Corcyra cephalonica and its effect on properties of milled rice

Radio frequency (RF) heating has the potential to be developed as an alternative non-chemical disinfestation method. In contrast to microwave (MW), RF exhibited higher penetration depth, which helps RF to be a useful technique in disinfesting packaging foods. A 3 kW, 27.12 MHz RF system was used to validate the practical of radio frequency technology for rice moth (Corcyra cephalonica) control in milled rice. Rice samples were placed in the polystyrene bag and moved at a speed of 0.8 m/min, and heated in the RF system with intermittent mixing. Four electrode gaps and five sample thicknesses were chosen to confirm the optimal conditions of RF treatment. The results showed that the sample thickness of 15 mm and electrode gap of 40 mm could provide the optimum heating rate for rice. Mortality of each stage (adult, larva, egg) of C. cephalonica increased with increasing heating temperature and reached 100% while RF heated 180 s (45.8 °C), 300 s (56.9 °C), and 420 s (70 °C), respectively. No C. cephalonica was determined in the samples during 45 days storage incubation period at RF treatment to 70 °C. There were no significant differences between control and RF treated samples in quality parameters (moisture, protein, fat, gelatinization, and sensory attributes). Therefore, RF treatment may provide a practical and effective method for disinfesting milled rice without affecting product quality.     

Effect of Pretreatment on Quality of Sweet Peach Pickles

Experiments were designed to increase the amount of fruit and reduce the sugar used in each container of sweet peach pickles without substantially altering the existing commercial process. Small whole (with seed in) peeled peaches were preheated in atmospheric steam, water and syrup in temperature ranges of 71–100°C for periods of time ranging from 3–6 min, then hot filled and processed as usual. Results showed that heating in atmmospheric steam-air mixture at 93°C for 4 min produced a significant increase in the number and weight of peaches per jar and a reduction of sugar without changing the quality significantly. Results of a test commercial pack revealed about 25% saving in syrup, and an average increase of four serving per jar to the consumer.     

Characterization and Multivariate Analysis of Physical Properties of Processing Peaches

Characterization of physical properties of fruits represents the first vital step to ensure optimal performance of fruit processing operations and is also a prerequisite in the development of new processing equipment. In this study, physical properties of engineering significance to processing of three popular cultivars of clingstone peaches were evaluated, including dimensional parameters, mass, dimensional ratios, aspect ratio, elongation index, sphericity, bulk density, texture, color, and flavor. Based on these physical properties, multivariate analysis of variance (MANOVA), canonical variate analysis (CVA), principal component analysis (PCA), and partial least squares and linear discriminate analysis (PLS-LDA) were applied to qualitatively and quantitatively discriminate the cultivar difference. Results showed that the studied peach cultivars had significantly different (p?<?0.05) geometric characteristics. The peaches can be classified based on the cheek diameter (D_c) into three different size categories, including small- (D_c less than 60 mm), medium- (D_c between 60 mm and 70 mm), and large- (D_c higher than 70 mm) sized peaches. The peach flesh firmness significantly (p?<?0.05) decreased with the increase of peach size, while the pit dimensions were independent of peach size. There were no apparent distinctions in color characteristics, bulk density, and sugar content among the three cultivars. The measurements and quantitative discrimination of peach properties in this study would benefit equipment design and process innovation to enhance the processing efficiency and quality of processed peaches.     

Tomato peeling by ohmic heating: Effects of lye-salt combinations and post-treatments on weight loss,peeling quality and firmness

Ohmic heating without lye has shown promise in tomato peeling; however the use of lye is known to yield high peeled-product quality. This investigation was aimed at determining whether a combination of ohmic heating and low lye concentrations could be synergistic. The results indicated that 0.01/0.5% NaCl/KOH at 2020 V/m was the best condition for tomato peeling in terms of quality, weight loss, and peel cracking time. Further, the treatment showed weight loss that was not significantly different from conventional lye peeling at 7% NaOH and 7% KOH (p < 0.05). NaCl/NaOH mixtures also showed good results, but the quality of products was lower than that using the same concentration, but a higher field strength with NaCl/KOH mixtures. However, no improvement was found using NaCl/CaCl₂ and NaCl/NaOH/CaCl₂ mixtures which were also found difficult to use due to turbidity and cleaning difficulties. A post-peeling treatment by ohmic heating was investigated to improve firmness of ohmically peeled tomatoes. It was found that the best conditions were 2% CaCl₂ solution at a field strength of 403 V/m for 1 and 5 min, and 484 V/m for 5 min.Industrial RelevanceOur earlier work had shown that ohmic heating resulted in peeling of tomatoes that were immersed in salt solutions. The current work details the impact of using small concentrations of lye (either sodium or potassium hydroxide) on peeling loss and quality. Also, we investigate the potential use of calcium chloride, both as peeling solution or as a post-peeling infusion as it impacts firmness of tomatoes. We show that there are ranges of operating conditions which provide yield and quality comparable to conventional lye peeling at far lower lye concentrations, resulting in potentially significant environmental benefit to companies currently using lye peeling.     

Stability of carotenoids in tomato juice during processing

The stability of carotenoids in tomato juice as affected by various processing treatments was studied. Fresh tomatoes were crushed, hot-broken at 82 °C, screened and the juice was subjected to the following treatments: (1) heated at 90 °C for 5 min prior to canning; (2) heated in water at 100°C for 30 min after canning; (3) heated at 121°C for 40 s before canning (high-temperature-short-time treatment). The results showed that 16 carotenoids, including all-trans plus cis forms of lutein, lycopene and -carotene, were present in tomato juice. Most cis isomers of carotenoids showed inconsistent change during heating. The high-temperature-short-time treatment generated the highest yield of all-trans plus cis forms of lutein and lycopene, followed by heating at 90 °C for 5 min and heating in water at 100 °C for 30 min. Only a minor change in -carotene was observed for these heating treatments.