Effects of dehydration temperatures on colour and polyphenoloxidase activity of Amasya and Golden Delicious apple cultivars

During dehydration at different temperatures (60, 70 and 80 °C) of Amasya and Golden Delicious apple cultivars, changes in colour, polyphenoloxidase activity (PPO), browning index and hydroxymethylfurfural (HMF) content were studied. Effects of dehydration time on the L* values of both cultivars were not significant. Only Amasya samples dehydrated at 80 °C were found to have significantly higher L* values than the remaining samples. In all cases, Golden Delicious samples had higher L* values than those of the Amasya cultivar. a* values of samples increased within the first hour of dehydration and then remained almost unchanged. The enzyme activity showed a rapid decrease in the first hour of dehydration and residual enzyme activities (%) reached 9.8%, 5.3% and 4.5% for Amasya, and 17.4%, 10.3% and 4.6% for the Golden Delicious cultivar at 60, 70 and 80 °C, respectively. In all final samples the residual enzyme activities were around 1%. The highest browning values were observed at the second hour of dehydration at 60 and 70 °C and the first hour of dehydration at 80 °C. In all conditions Amasya apples had a higher browning tendency. The presence of HMF was detected only at the 4th hour of dehydration at 80 °C for both cultivars. Effects of dehydration temperature on colour and PPO of the final product were insignificant. However, an important effect of temperature was determined on the browning index of Golden Delicious samples. The lowest browning tendency was measured on samples dehydrated at 80 °C. The results showed that cultivar and dehydration temperature had considerable effect on the browning of apple slices. Copyright © 2006 Society of Chemical Industry     

Browning susceptibility of minimally processed Baby and Romaine lettuces

 This study was conducted to determine the effects of cultivar, tissue susceptibility and storage temperature on the keeping quality of minimally processed Baby and Romaine lettuces. Midrib and photosynthetic tissues were lightly processed and stored for up to 7 days at 5  °C and 13  °C. Changes in L ^* and a ^* values and absorbance at 430 nm were compared. The relationship between polyphenols, phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO) activities and browning was examined. Measurements of L ^* and a ^* values on midribs showed that browning discoloration was the same for Baby as for Romaine lettuces and there was no relationship for temperature. In addition, L ^* and a ^* values in photosynthetic tissue indicated a decrease in green pigmentation during storage, especially at 13  °C. For both kinds of tissue at the end of cold storage an increase in soluble brown polymers was detected. In midribs, total phenolics increased significantly throughout the storage period because of the tissue-wounding response. The photosynthetic tissue had a higher phenolic content than the midrib one. For both kinds of tissue an increase in PPO activity occurred throughout cold storage. On the other hand, PAL activity in midrib tissue only increased initially, followed by a slow decline to reach normal levels. Browning potential estimated by L ^* values correlated significantly (P>95%) with PPO activity and with absorbance at 430 nm for Romaine lettuce. Based on colour and browning potential no differences between Romaine and Baby lettuce cultivars were observed. However, photosynthetic tissue was the most suitable tissue for the preparation of minimally processed salad mixes because of its high phenolic content. Received: 28 September 1998     

Evaluation of four types of resistant starch in muffins. II. Effects in texture,colour and consumer response

In this study, the influence of the addition of four types of resistant starch containing ingredients on texture, colour and consumer acceptability of muffins was studied. Two resistant starch type 2 (RS2) and two resistant starch type 3 (RS3) containing ingredients were used. The addition of all RS types decreased the instrumental texture parameters, but the lowest values were shown by the RS3-containing muffins. No significant differences were found in L* parameter between the control (with no RS addition) and the RS3-containing muffins. On the contrary, RS2-containing muffins showed a lighter colour (L* significantly higher) in comparison to the control and the RS3-containing muffins, which was obvious for the human eye (ΔE* > 3). RS3-containing muffins showed the lowest sensory acceptability while RS2-containing muffins showed no significant differences in all the sensory attributes in comparison to the control.     

Changes of colour and pH in fish musculature after ionizing radiation exposure

Irradiation of meat causes sensory changes as do other technological methods. The most significant sensory and quality indicator of meat is colour; therefore, the effect of irradiated pieces of fish was studied in relation to colour changes. Colour was measured at the musculature of Oncorhynchus mykiss. The parameters of colour, L*, a* and b*, were determined with the portable Superchroma S-Spex (Braive) spectrophotometer in the CIELAB system before irradiation (3 h post mortem) and after irradiation (⁶⁰Co source, a dose of 3 kGy and a dose rate of 3.33 kGy h^–1) (5 h post mortem). The change of L* was identical for both irradiated and nonirradiated samples. This change may be caused by maturation of fish flesh. a* was identical and b* decreased. This effect differs from that of irradiated pork. The decrease of the pH was identical for both irradiated and nonirradiated samples. This change may be caused by maturation of fish flesh.     

Comparison of physicochemical,microscopic and sensory characteristics of ecologically and conventionally grown crops of two cultivars of tomato (Lycopersicon esculentum Mill.)

BACKGROUND: Numerous studies have compared ecologically produced foods with conventionally produced competitors, with contradictory results. In this work we investigated the physicochemical, microscopic and sensory properties of two tomato cultivars (Lladó and Antillas), which were grown both ecologically and conventionally. RESULTS: The physicochemical variables size, weight, firmness, total acidity, pH, total solids content, lycopene content and CIELab a*, b*, a*/b*, C* and h* were all significantly influenced by cultivar, as were the sensory variables external colour, internal colour, external aroma intensity and flavour persistence. Compared with conventionally grown tomatoes, ecologically grown tomatoes had larger total solids contents and larger values of the CIELab colour parameters b*, C* and h*, but smaller sizes and weights and smaller values of the CIELab parameter ratio a*/b*; however, these physicochemical differences were insufficient for growing method to have a significant influence on any of the sensory attributes that were evaluated. Microscopy showed the influence of cultivar on lycopene content, but no other structural differences were observed between the two cultivars or between tomatoes grown by different methods. CONCLUSIONS: The statistically significant differences found in this study were mainly between cultivars rather than between tomatoes grown using different management practices. Copyright © 2009 Society of Chemical Industry     

Non-destructive and objective methods for the evaluation of the maturation level of olive fruit

The maturation level of two olive varieties (Olea europaea, cvs. Arbequina and Picual) was objectively evaluated using two non-destructive methods: checking the fruit firmness using a hand densimeter, and the skin colour with a portable colourimeter. These methods were compared with the Ripening Index (RI), habitually used by olive oil industry, and based on the subjective determination of skin and flesh colour. The values of skin colour [L*(b*–a*)/100] only monitor the olive maturation in both varieties, when the olive is losing its initial green colour, while fruit firmness is decreasing throughout the maturation process. Fruit firmness is directly related to RI and could be useful in objectively estimating the maturation level of the olives.     

A colorimetric study of oenin copigmented by procyanidins

A colorimetric method was used to analyse the influence of procyanidin structure on colour changes of malvidin 3‐O‐glucoside (oenin) solution resulting from copigmentation. The study was performed in hydroalcoholic citrate/phosphate buffer solution (120 g L^?1) at pH 3.6 and ionic strength 0.2 mol L^?1. Chromatic L*, a* and b* coordinates (CIELAB, D65/10° illuminant/observer condition) obtained from spectral curves recorded between 360 and 830 nm allowed the calculation of lightness L*, chroma C* and hue angle h_ab. In general, addition of copigment induced colour enhancement (loss of lightness and increased chroma). The prevailing parameters affecting colour changes were lightness and chroma for monomers and lightness and hue for procyanidins B5 and B8 (C4–C6 dimers). A small blueing effect was observed only for catechin monomer‐copigmented solutions. For procyanidin copigments, as the structural complexity of the copigment increased, the hue angle moved to yellower values. The ester gallate of dimer B2 produced the strongest modification of colour attributes of oenin solution. Copyright © 2006 Society of Chemical Industry     

The effect of packaging treatment on the storage quality of minimally processed bunched onions

Storage quality of minimally processed (MP) bunched onions, as affected by plastic film packaging, was investigated to determine the optimum packing method for this vegetable product. Five different packaging treatments, including two passive modified atmosphere packaging (MAP), two active MAP and a moderate vacuum packaging (MVP), were used for MP bunched onions. Quality attributes of the samples were evaluated periodically in terms of weight loss, colour, decay ratio, microbial counts and sensory properties during storage at 10 °C for 28 days. Various sealed‐packaging treatments did not significantly influence changes in colour of white stem and green leaf tissues, flesh weight loss and microbiological populations including mesophiles, psychrotrophs and lactic acid bacteria. However, sensory attributes and disease incidence were affected by packaging type. MVP with a gas‐permeable plastic film retained better quality bunched onions, with reduced microbial decay and visual sensory aspects, as compared with the other packages.     

Effect of high oxygen modified atmosphere on post‐harvest physiology and sensorial qualities of mushroom

The changes in physiology and sensorial qualities of mushroom stored at 2 °C for 12 days under high oxygen (100% O₂, 80% O₂) atmosphere and air had been investigated. Respiration rate was suppressed in mushroom in 80% O₂ and 100% O₂. No significant differences were found between 80% O₂ and 100% O₂. Weight loss was not more than 1.5% in all treatments. Weight loss and firmness of mushroom held in high oxygen were significantly (P < 0.05) higher than in air. Total soluble solid (TSS) was only slightly affected by high oxygen treatment. High oxygen, especially 100% O₂ treatment was effective at reducing browning degree and electrolyte leakage of mushroom. The surface colour of mushroom changed slightly before tenth day under high oxygen treatment. From day 2 the L‐value of mushroom flesh was significantly (P < 0.05) lower under air atmosphere compared with high oxygen treated mushroom. High oxygen, especially 100% O₂ was effective at inhibiting discoloration. The PPO activity of mushroom was significantly (P < 0.05) higher in 100% O₂ compared with air treatment. The POD activity was highest in high oxygen at eighth day, then reduced. High oxygen, especially 100% O₂ was effective at maintaining the quality of mushroom.     

Poststorage Behavior of Apple Fruit After Low Oxygen Storage as Influenced by Temperatures During Storage and in Transit

‘Delicious’, ‘Newtown’ and ‘Granny Smith’ apples (Malus domestica Borkh.) maintained acceptable flesh firmness and high levels of titratable acids and soluble solids after 9 months of storage in 1% 0₂ at either 0°C or 3.3°C. Low-0₂-stored ‘Delicious’ were kept at 0°C for 6 wk without developing physiological disorders before or after 8 days of ripening at 20°C. Storage at 3.3°C caused ‘Delicious’ to soften faster during 6 wk of post-storage holding plus 8 days of ripening. ‘Newtown’ apples developed flesh browning and alcohol flavor after 9 months of low 0₂ storage at 0°C. ‘Newtown’ fruit stored at 3.3°C developed only minimal incidence of flesh browning and alcohol flavor. ‘Granny Smith’ fruit were free from scald, core flush, flesh browning and alcohol flavor after low 0₂ storage, regardless of storage temperature. However, core flush and flesh browning appeared when ‘Granny Smith’ were kept for 6 wk at 0°C plus 8 days at 20°C.     

Optimization of the roasting of robusta coffee (C. canephora conillon) using acceptability tests and RSM

With the objective of optimizing the roasting of robusta coffee (Coffea canephora Conillon), a two factor central composite design (11 samples) was used to optimise the settings for roasting time and the initial internal temperature of the roaster drum on response variables of acceptance with 25 consuming assessors, for the sensory attributes of beverage aroma, flavour and colour. Predictive models were also obtained for the instumental measurement of the colour of the beans and ground coffee. The optimum range for roasting was shown to be a time of 22–28 min at a temperature of 225–230°C, corresponding to the degree of roasting characterized by the following range of colour of roasted robusta beans: L* between 37.05 and 40.69, a* between 2.29 and 4.15 and b* between 2.70 and 6.29.     

The effect of par‐baking and frozen storage time on the quality of cup cake

The effects of frozen storage and initial baking time of par‐baked cake on baking loss, volume, moisture, colour and textural properties of cake obtained after thawing and rebaking were investigated. Cakes, par‐baked at 175 °C for 15, 20 and 25 min, were stored at ?18 °C for 3, 6 and 9 months. After storage, par‐baked cakes were thawed and rebaked at 175 °C for 10, 15 and 20 min. Baking loss, moisture content, L and +b colour values, firmness, gumminess and chewiness of the resulting full‐baked cakes were significantly affected by both par‐baking and frozen storage time, while specific volume, cohesiveness, springiness and resilience values were significantly affected by frozen storage time. The increase in the time of frozen storage of the par‐baked cake leads to a decrease in the quality of the rebaked cake, namely an increase of baking loss and cake crumb firmness, and a loss in the moisture content and specific volume. Moisture of cake crumb, L and +b colour values, firmness, gumminess and chewiness significantly increased as the par‐baking time increased. However, regarding baking loss, specific volume, moisture content and textural properties, 3‐month intermediate storage at ?18 °C and 20‐min initial baking time gave the best result among the cakes produced by using the two‐step baking procedure.     

High pressure thermal processing of pears: Effect on endogenous enzyme activity and related quality attributes

The effect of high pressure-thermal (HPT) processing (600 MPa, 20–100 °C) on the activity of pear enzymes and related quality attributes was investigated. HPT processing at 20 °C for 5 min resulted in 32%, 74% and 51% residual activities of polyphenol oxidase (PPO), peroxidase (POD) and pectin methylesterase (PME), respectively. Increasing processing temperature to 40 and 60 °C reduced the level of PPO and POD inactivation, with the maximum residual activities of 64% and 123%, respectively observed after 3-min treatments at 40 and 60 °C. Overall, HPT at 20 to 60 °C had minimal effect on quality, although enzymatic browning was observed upon air exposure. HPT at 80 to 100 °C caused almost complete inactivation of PPO and POD with 90% and 92% inactivation respectively after 3-min processing at 100 °C, which reduced browning upon air exposure. Nevertheless, the lowest texture retention of 22% was observed under this condition.Industrial relevanceThe study examined the effects of combined high pressure thermal processing on quality related pear enzymes and related instrumental quality attributes such as colour and texture. The study enabled identification of processing regimes for enzyme inactivation and quality retention. The excellent quality retention following HPP at 20 to 40 °C makes this condition suitable for ‘fresh-like’ small portion products for immediate consumption after unpacking that do not require complete PPO and POD inactivation. On the other hand, the almost complete inactivation of oxidative enzymes PPO and POD at 100 °C makes this condition more appropriate for the production of bulk products for food service applications or pureed ingredients for baby food, or pear pieces for yoghurt, that require PPO inhibition but not necessarily high firmness retention.     

Physiological and biochemical changes of different fresh-cut mango cultivars stored at 5 °C

Treatments to inhibit browning, decay and to extend shelf life of ‘Keitt’, ‘Kent’ and ‘Ataulfo’ mango cultivars as a fresh‐cut produce were investigated. Combinations of calcium chloride (CaCl₂), antioxidants [ascorbic acid (AA), citric acid (CA)] and two commercial film coatings resulted in a reduction of browning and deterioration of fresh‐cut mangoes stored at 5 °C, especially for the Ataulfo cultivar. The use of CaCl₂ + AA + CA significantly reduced colour deterioration, loss of firmness and did not affect sensory characteristics of fresh‐cut mango, with a larger effect in the Ataulfo cultivar. In general, these treatments prevented loss of sugar and vitamin C of cubes during storage at 5 °C. Shelf life of this cultivar was 21 days, while that of Keitt and Kent was only 9 and 12 days, respectively. There is a correlation between carotene and vitamin C content of Ataulfo mango and its longer shelf life compared with the other cultivars.     

Kinetic models of non‐enzymatic browning in apple puree

The effects of thermal treatments on 11 °Brix apple puree were studied at temperatures from 80 to 98 °C. Colour changes (measured by reflectance spectroscopy, colour difference, L*, a* and b* and the evolution of 5‐hydroxymethylfurfural (HMF) and sugars (hexoses and sucrose) were used to evaluate non‐enzymatic browning. A kinetic model based on a two‐stage mechanism was applied to the evolution of colour difference and a*. A first‐order kinetic model was applied to L* evolution, while the evolution of absorbance at 420 nm (A₄₂₀) of the liquid fraction was described using a zero‐order kinetic model. Thermally treated samples became more reddish and suffered a slight loss of yellow hues. The effect of temperature on the kinetic constants was described by an Arrhenius‐type equation. The presence of pulp in the samples led to activation energies for A₄₂₀ and sucrose which were lower than those found previously for clarified juices with the same soluble solids content. © 2000 Society of Chemical Industry     

Quality changes during storage of sous vide cooked green beans (Phaseolus vulgaris)

 The acceptability and quality of sous vide cooked green beans (Phaseolus vulgaris) were investigated during chilled storage. A suitable heating procedure was established whereby 2.0-kg packages were heat processed at 90°C for 25 min, corresponding to an average pasteurization value, PV_70,10, of 14 min. During storage for up to 25 days at 3°C drip loss, pH, colour (Minolta L ^* a ^* b ^*), texture (Instron) and microbiological stability were examined and sensory characteristics evaluated by a trained sensory panel. No marked changes in texture, drip loss, pH or microbiological counts were observed but a change of colour from green to olive green was observed by both objective and sensory analyses. This detrimental change in colour, which had begun during the first week, was the limiting factor for shelf-life during storage. Subsequent reheating, however, resulted in further colour changes which partially obscured the initial differences observed during the storage period. Storage for more than 1 week resulted in undesirable quality changes in the odour and flavour of the green beans. Therefore, a maximum shelf-life of 8 days at 3°C was recommended. Inoculation trials showed that psychrotrophic Bacillus cereus were able to germinate and grow to levels of 10⁷ g^–1 in the packages at abuse temperatures (7°C and 17°C), whereafter numbers declined. Received: 21 April 1997     

Influence of quinoa roasting on sensory and physicochemical properties of allergen‐free,gluten‐free cakes

The objectives of this study were to determine pasting properties of non‐roasted (NR) and roasted quinoa (RQ) and to investigate the effect of RQ on consumer acceptance and physicochemical properties of an allergen‐free, gluten‐free cake formulation. Quinoa seeds were roasted at 177 °C for 15 (R15), 30 (R30) and 45 min (R45), and flours were analysed for pasting properties. Five cakes including a commercial chocolate cake (CCC) and cakes made with NR and RQ flours were evaluated for preference by fifty panelists. Quality parameters included colour, water activity, moisture content, firmness, weight and height. Peak and final viscosity increased with roasting time. The NR cake had the highest sensory scores for appearance, colour and texture. On flavour and overall acceptability, CCC was the highest. Regarding quality data, CCC, NR and R15 cakes had similar L* values, while CCC had the lowest a*, b*, a_w, moisture content and firmness values.     

Delayed harvest and cold storage period influence ethylene production,fruit firmness and quality of ‘Cripps Pink’ apple

The effects of harvest date and cold storage period on ethylene production, fruit firmness and quality of ‘Cripps Pink’ apple were investigated. Fruit were harvested from Perth Hills and Donnybrook (Western Australia) at commercial maturity (CM), 2, 4 and 6 weeks after CM prior to 0, 45, 90 and 135 days cold storage in 2003 and 2004. Delayed harvest significantly increased ethylene production, CIE values a* and C* at both locations in 2 years. Delayed harvest and extended cold storage period increased the internal ethylene production and reduced fruit firmness, soluble solids concentration: titratable acidity (SSC:TA) ratio and reduced CIE values L*, b*, h° during both years and locations. Fruit harvested 2 weeks after CM can be cold‐stored for 90 days with acceptable fruit quality. If the fruit is intended to be sold fresh immediately in local markets, the harvest can be delayed up to 6 weeks after CM to harness substantially improved fruit colour with acceptable fruit quality.     

Edible coatings enriched with essential oils for extending the shelf‐life of ‘Bravo de Esmolfe’ fresh‐cut apples

Edible coatings based on sodium alginate (AL) and pectin (PE) at 1% and 2%(w/v) enriched with eugenol (Eug) and citral (Cit) at minimum inhibitory concentrations (MIC) (0.10% and 0.15%) and double MIC were used to preserve the quality of fresh‐cut apples ‘Bravo de Esmolfe’. Samples were taken, through 14 day at 4 °C, for analysis of colour CIE(L*h°C*), firmness, °Brix, weight loss, antioxidant activity (TEAC), microbial growth and taste panels. With those quality characteristics, three groups were formed by the principal component and hierarchical cluster analysis, for each coating base (AL or PE). Based on, for each quality parameter measured, the mean closest value to the one at harvest for colour, higher value for firmness, °Brix and TEAC, and lower value for weight loss and microbial spoilage, the best group was selected for AL and PE. From each group, two edible coatings with the highest scores in overall acceptability were selected for fresh‐cut apples: AL2% + Eug 0.1%, AL2% + Cit 0.15% + Eug 0.1%, PE 2% + Cit 0.15% and PE 2% + Eug 0.2%.     

Effect of High Hydrostatic Pressure and Temperature on Enzymatic Activity and Quality Attributes in Mango Puree Varieties (cv. Tommy Atkins and Manila)

Pectinmethylesterase (PME), peroxidase (POD), and polyphenoloxidase (PPO) residual activities (RAs) and physicochemical parameters (pH, total soluble solids (TSS), water activity (a_w), viscosity and color) of Tommy Atkins and Manila mango purees (MPs) were evaluated after high hydrostatic pressure (HHP) treatments at 400–550 MPa/0–16 min/34 and 59 °C. HHP treatment applied at 59 °C induced higher enzyme inactivation levels than the treatment applied at 34 °C in both MPs. The lowest RA of PME (26.9–38.6%) and POD (44.7–53%) was achieved in Manila MP treated at 450 MPa/8–16 min/59 °C and 550 MPa/4–16 min/59 °C, respectively. Otherwise, Tommy Atkins puree pressurized at 550 MPa/8–16 min/59 °C had the lowest PPO RA (28.4–34%). A slight decrease in pH and TSS values of both HHP-processed MPs at 34 and 59 °C was observed, whereas the a_w remained constant after processing. The viscosity of MPs tended to augment up to 2.1 times due to the application of HHP. No significant changes were observed in color parameters of Tommy Atkins MP, except at 550 MPa and 59 °C where higher yellow index (YI) (122.4?±?3.3) and lower L* (37.3?±?5.3) were obtained compared to the untreated MP. HHP caused an increase in L* values in Manila MP, whereas no clear trend was observed in YI. HHP processing at 550 MPa combined with mild temperature (59 °C) during 8 min could be a feasible treatment to reduce enzymatic activity and preserve fresh-like quality attributes in MP.