Influence of drying treatments on the physical and chemical properties of cucumber

This work aimed at determining the properties of cucumber exposed to convective air drying and freeze-drying. The samples were analysed in terms of colour, texture, chemical properties (moisture content, fibre, ash, vitamin C and sugars), phenolic compounds and antioxidant activity in fresh and after drying. The trials in the convective chamber were done at 40 and 60 °C, in the drying tunnel at 60 °C and in the freeze dryer at ?50 °C. The results showed that the antioxidant activity and the phenolic compounds were not affected by any of the drying treatments tested, since the values were quite similar in the fresh product as compared to the dried cucumbers. With respect to colour, the freeze drying treatment was identified as the one originating less colour change, when compared with the colour of the fresh product. Finally, texture was less affected by drying in the chamber at 40 °C and freeze drying.     

Influence of hot-air temperature on drying kinetics,functional properties,colour, phycobiliproteins,antioxidant capacity,texture and agar yield of alga Gracilaria chilensis

Effect of air temperature on drying kinetics, functional properties, phycobiliproteins (PE and PC), colour, antioxidant capacity, total phenolic content, texture and agar yield during drying of algae Gracilaria chilensis were studied. Drying curves were satisfactorily simulated with the Weibull model at 40, 50, 60 and 70 °C. Both, Rehydration Ratio and Water Holding Capacity decreased with increasing temperature. Low drying temperatures showed higher PE and PC concentration than higher temperatures (e.g. 60 and 70 °C). In particular, dehydration at 50 °C presented the higher values of these two pigments. The three chromatic coordinates (L1, a1 and b1) were influenced by the treatments showing the highest ?E value at 50 °C. Antioxidant activity as well as texture were notably influenced by increasing drying temperatures. At 70 °C, a maximum agar yield of 40 g/100 g was obtained. Results indicated that agar yield and quality of dried algae showed opposite behaviours leading to a compromise decision on operating conditions involved in the overall process. According to these results, optimization of the process based on economical aspects of the final dried product is required.     

Effect of Air-Drying Conditions on Physico-chemical Properties of Osmotically Pre-treated Pomegranate Seeds

The drying of pomegranate seeds was investigated at 40 °C, 50 °C and 60 °C with air velocity of 2 m/s. Prior to drying, seeds were osmodehydrated in 55 °Brix sucrose solution for 20 min at 50 °C. The drying kinetics and the effects of osmotic dehydration (OD) and air-drying temperature on antioxidant capacity, total phenolics, colour and texture were determined. Analysis of variance revealed that OD and air-drying temperature have a significant influence on the quality of seeds. Both anthocyanin and total phenolic contents decreased when air-drying temperature increased. The radical diphenylpicril-hydrazyl activity showed the lowest antioxidant activity at 60 °C. Both chromatic parameters (L*, C* and h°) and browning index were affected by drying temperatures, which contributed to the discolouring of seeds. The final product has 22%, 20% and 16% of moisture; 0.630, 0.478 and 0.414 of a _w; 151, 141 and 134 mg gallic acid equivalent/100 g fresh matter (FM) of total phenolics; 40, 24, 20 mg/100 g FM of anthocyanins and 46%, 39% and 31% of antioxidant activity, for drying temperatures of 40 °C, 50 °C and 60 °C, respectively. In view of these results, the temperature of 40 °C is recommended as it has the lowest impact on the quality parameters of the seeds. Differential scanning calorimetry data provided complementary information on the mobility changes of water during drying. Glass transition temperature (Tg′) depends on moisture content and as consequence, on drying conditions. In fact, Tg′ of seeds dried at 60 °C (Tg′ = −21 °C) was higher than those dried at 50 °C (Tg′ = −28 °C) or 40 °C (Tg′ = −31 °C) and osmodehydrated seeds (Tg′ = −34 °C). During OD and drying process, the texture of seeds changed. The thickness of seeds shrank by 55% at 60 °C.     

Tomato peel drying and carotenoids stability of the extracts

Tomato peels were firstly dried by different methods (hot air, freeze‐drying, and fluidized bed drying) to evaluate the recovery of lycopene, β‐carotene and DPPH radical scavenging activity. Comparison of the results showed that hot air drying at 50 °C was a suitable method and alternative to freeze‐drying to preserve carotenoids compounds and antioxidant activity in tomato peels. Then, ethanol/ethyl acetate (1:1) extracts from tomato peel, previously dried at 50 °C by hot air, were submitted to heat (100 °C) and light treatment (1000 lumen) to evaluate their stability as natural food dyes. Heating of the extracts caused a progressive reduction of total carotenoids, up to about 30% after 250 min of treatment, whereas the colour at the end of heat treatment showed small changes, with an overall colour difference (?E) equal to 7. Fluorescent lighting treatment showed an almost total degradation of carotenoids in the extracts after 48 h combined with a fading colour.     

Potentially bioaccessible phenolics,antioxidant capacities and the colour of carrot,pumpkin and apple powders – effect of drying temperature and sample structure

The study aimed to examine carrot, pumpkin and apple powders produced by hot-air-drying (50, 60, 70 °C) of samples with different levels of fragmentation (cut, grated, blended). The drying temperatures and sample structure were shown to be important determinants of the quality of the powders. The best colour stability of carrot, pumpkin and apple was found for the grated sample dried at 70 °C, the blended sample dried at 70 °C and the blended sample dried at 70 °C, respectively. The highest antiradical capacity and reducing power were found for powders obtained after drying the cut samples at 70 °C. Total phenolics and free radical quenchers were well bioaccessible in vitro. In turn, the reducing power was markedly reduced after drying at 50 °C. The analysed powders are a valuable source of concentrated bioactive ingredients, which predisposes them to serve as functional food components.     

Effect of previous frozen storage on quality changes of grass carp (Ctenopharyngodon idellus) fillets during short‐term chilled storage

The effect of chilled, frozen and freeze‐chilled storage on quality of grass carp fillets and soups was evaluated by sensory score, total aerobic counts and biochemical quality. Fish fillets were stored at 4 °C for 6 days (T1), ?40 °C for 12 h and then at ?20 °C for 5 days (T2), ?40 °C for 12 h and then at ?20 °C for 5 days, followed by at 4 °C for 4 days (T3). T1 showed higher sensory score, salt‐soluble protein content, better colour and texture qualities than T2 and T3 within 3 days. All fillets kept good quality based on the acceptable limit of sensory score, total volatile basic nitrogen and total aerobic count during storage time. According to the transportation and retail time, chilled storage is appropriate when it is within 3 days. If it extends for 5 days, freeze‐chilling treatment keeps better quality, but later chilled fillets should be retailed within 4 days.     

Effect of blanching and drying treatments on quality of bamboo shoot slices

The enzymes activity, texture, pectin, microstructure and colour change in bamboo shoots (Dendrocalamus latiflorus) were examined to evaluate the effect of blanching and drying treatments on quality of bamboo shoot slices (BSS). Peroxidase (POD), phenylalanine ammonia‐lyase and polyphenol oxidase in BSS will become completely inactive at 95 °C for 6‐, 9‐ and 12‐min blanching treatments, respectively. The hardness and protopectin (PP) content decreased after the blanching treatment. Meanwhile, the content of water‐soluble pectin increased initially and then decreased gradually during the blanching. After the blanching treatment, the L* and a* of BSS decreased, while b* increased, ΔE > 2. The hardness of rehydrated BSS decreased by 43.57% after freeze drying (FD), which, however, decreased more after hot air drying (HAD). The pectin of rehydrated BSS was also determined to explain the hardness change in BSS. The BSS acquired similar microstructure of fresh samples after FD, while microstructure of BSS was severely damaged after HAD. The colour of BSS changes significantly after drying treatment. However, FD can maintain better colour of BSS than HAD. The results may provide a reference for industrial production of BSS.     

Effect of vacuum‐drying,hot air‐drying and freeze‐drying on polyphenols and antioxidant capacity of lemon (Citrus limon) pomace aqueous extracts

The aim of this study was to investigate the effect of freeze‐drying, hot air‐drying and vacuum‐drying at 70, 90 and 110 °C, on dried lemon pomace polyphenols and antioxidant capacity. The total phenolic content and antioxidant capacity were higher in lemon pomace dried by hot air or under vacuum than those dried by freeze‐drying and increased as the temperature increased. The highest total flavonoid content was recorded in the pomace dried under vacuum at 70 and 90 °C. Lemon pomace dried by freeze‐drying had the highest neohesperidin content, whereas pomace dried under vacuum at 70 °C had the highest rutin and p‐coumaric acid content. The highest gallic acid content was recorded in the pomace dried by hot air at 110 °C. The results of this study indicate that drying technique should be carefully selected according to the bioactive compounds aimed to be extracted.     

Effect of non‐isothermal processing and moisture content on the anthocyanin degradation and colour kinetics of cherry pomace

Anthocyanins (ACY) and colour changes in cherry pomace under non‐isothermal processing were investigated. Pomace at moisture levels of 70% (MC‐70), 41% (MC‐41) and 25% (MC‐25) was heated at 126.7 °C in a retort for 25, 40 and 60 min. Total ACY, Hunter colour values, total colour difference (ΔE), chroma, hue angle (h°) and browning index (BI) were analysed. Thermal degradation kinetics for colour parameters were determined using zero‐ and first‐order models. ACY degradation increased with heating time and ranged from 34 to 68% for 25 and 60 min heating, respectively. The half‐life of ACY was 38, 33 and 27 min for MC‐70, MC‐41 and MC‐25 pomace, respectively. The ΔE increased with increasing heating time, whereas BI exhibited an inverse trend. Except for ?E for MC‐70, the zero‐order kinetic model showed better fit (R² = 0.85–0.97) to experimental data than the first‐order kinetic model for Hunter colour b values and ?E.     

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.     

Influence of drying conditions on colour,betacyanin content and antioxidant capacities in dried red-fleshed dragon fruit (Hylocereus polyrhizus)

In this study, drying of red-fleshed dragon fruit at different temperatures (40, 50, 60, 70 and 80 °C) and air velocities (1.0 and 1.5 m s⁻¹) was conducted under the specific humidity of 25 g H₂O kg⁻¹ dry air. The results showed that drying at higher temperatures resulted in shorter drying times. However, temperature and air velocity did not significantly affect the total betacyanin contents and antioxidant capacities in dried products. Seven betacyanins identified by LC-MS were betanin, isobetanin, phyllocactin, isophyllocactin, betanidin 5 –O-(6′O-3-hydroxybutyryl)-β-glucoside, isobetanidin 5 –O-(6′O-3-hydroxybutyryl)-β-glucoside and decarboxylated phyllocactin. In addition, the temperature increased the isomerisation of betacyanins. The most preferable condition for preserving the colour and betacyanin contents of red-fleshed dragon fruit was the drying at a temperature of 80 °C and air velocity of 1.5 m s⁻¹ since it could shorten the drying time and give a bright red colour to the dried product as well as it had no significant impact on the betacyanins.     

Effect of Pre-treatment and Drying Method on Colour Degradation Kinetics of Dried Salak Fruit During Storage

Effect of heat treatment on colour stability of dried salak fruit during storage was investigated by using hot air (40–90 °C), heat pump (isothermal and intermittent modes, 26–37 °C) and freeze-drying. Influence of pre-treatment on the colour property was studied as well by blanching the sample at three levels of temperature (50–70 °C). Total colour change (∆E*) was used to assess the colour degradation kinetics and quantify the degree of browning during processing and storage. It was found that the dried pre-treated sample under heat pump isothermal drying recorded the highest ∆E* value during storage followed by non-pre-treated samples under heat pump intermittent drying, freeze-drying, hot air-drying and heat pump isothermal drying. Weibull model is found to better fit the experimental data as compared with zero-order and first-order kinetics models. Analysis on the kinetics constants reveals that the heat treatment could affect the microstructure, water sorption properties and concentration of reacting species of the dried product. This in turn contributes to the colour changes of the dried product during storage.     

Effects of conventional and nonconventional drying on the stability of Bifidobacterium animalis subsp. lactis INL1

Freeze, spray, vacuum, microwave vacuum‐ and microwave freeze‐drying were applied to Bifidobacterium animalis subsp. lactis INL1. Freeze and microwave freeze‐drying showed the highest survival after drying. When a storage test (25 °C; oxygen) was performed, these cultures were the most sensitive ones at a_w = 0.23, but the addition of lactose improved their stability after 8 weeks. Flow cytometry was useful to assess viability after drying but not during storage. Our results show that dehydration technologies other than freeze‐drying might be suitable alternatives that deserve further investigation for the preservation of sensitive probiotic bacteria. Microwave drying rendered cultures of comparable characteristics to their conventional counterparts, requiring significantly shorter drying times.     

Effect of sub‐freezing storage (−6, −9 and −12 °C) on quality and shelf life of beef

Based on the results of low field nuclear magnetic resonance (LF‐NMR) in our current study (the frozen state of ?6, ?9 and ?12 °C were nearly the same with extremely low free water content), ?6, ?9 and ?12 °C was designated as sub‐freezing temperatures. The effects of sub‐freezing storage compared with conventional chilling (4 °C), superchilling (?1 °C) and conventional freezing (?18 °C) on the quality and shelf life of beef were analysed. Results showed that the shelf life of beef is extended to 84 and 126 day at ?6 °C and ?9 °C, respectively. However, the TVB‐N values of the samples stored at ?12 °C and ?18 °C remained below 15 mg/100 g even on 168 day. Furthermore, shear force, colour, pH, thiobarbituric acid reactive substances (TBARS) and sensory properties were also measured. Consequently, the sub‐freezing storage has significantly extended the shelf life of beef compared to chilling and superchilling (P < 0.05). Moreover, no significant difference (P > 0.05) was found between the indicators for quality and shelf life of samples stored at ?12 and ?18 °C throughout 168 days.     

Effect of Drying on the Color of Tarragon (Artemisia dracunculus L.) Leaves

The effect of drying conditions on the color of tarragon (Artemisia dracunculus L.) leaves was studied. Tarragon leaves were dried at temperatures of 40 to 90 °C with a constant airflow of 0.6 m/s. The samples were collected at 7%, 10%, 20%, and 30% moisture content wet basis for evaluation of the color change. The color parameters of fresh and dried leaves were measured by a colorimeter. The individual parameters of L*a*b* and L*C*h° color systems were evaluated and h° proved to be the best parameter to monitor color change. The smallest change of the color parameters was observed at 40 °C, in which temperature was low, and also at 90 °C, when drying time was short. The biggest change occurred at the temperatures of 50 to 70 °C. Most of the color change happened before the material reaches 35% moisture content. The combination of drying time and temperature defines the change of color.     

Changes in the texture,microstructures, colour and volatile compounds of pork meat loins during superheated steam cooking

We evaluated changes in the texture, colour, microstructure and volatile compounds of pork loins after superheated steam (SHS) cooking at 120, 140, 160 or 180 °C for 5, 10, 15 and 20 min. Results showed that the texture changed significantly with heating temperature and time. Hardness increased significantly with increasing temperature above 140 °C. Scanning electron microscopy micrographs showed that cooked pork with SHS had more complete muscle fibre bundle structure than that of pork in HA. The L* value indicating colour was significantly increased during the early period and then decreased, whereas the a* and b* values showed a continuous increase. Ninety-five volatile compounds were identified in cooked pork from SHS by gas chromatography/mass spectrometry with solid-phase microextraction. The amount of volatile compounds increased during cooking and decreased as cooking time increased and was well retained at 140 °C. Considering those variations, samples cooked at 140 °C showed better quality attributes.     

Physicochemical properties and storage stability of spray‐dried soya bean sprout extract

Amylase is a very important enzyme due to its wide food applications. To preserve amylase activity in soya bean sprout extract (SSE), SSEs were spray‐dried with 10% maltodextrin and 0–3% alginic acids, and their physicochemical properties and storage stability were compared with freeze‐dried one. SSE exhibited maximum amylase activity at pH 7.0 and 60 °C, with the most active substrate specificity towards soluble starch. Spray‐dried SSEs exhibited higher water solubility index (WSI) and in vitro relative amylase activity but lower water vapour sorption (WVS) and smaller particle size than freeze‐dried SSE. For spray‐dried SSEs, particle size, WSI and in vitro relative amylase activity increased while WVS decreased with increasing % alginic acid. This study demonstrated that spray drying of SSE, especially with 10% maltodextrin and 2% alginic acid, was effective in keeping amylase active and stable during 7‐week storage at room temperature (25 °C).     

Effect of muscle,ageing time and modified atmosphere packaging conditions on the colour,oxidative and microbiological stability of packed beef

The objective of this study was to evaluate the influence of two different vacuum ageing times (7 and 14 days) and the impact of the modified atmosphere packaging (MAP) configuration (gas/product ratios: 0.5 and 1 and gas composition: 70% O₂ + 30% CO₂ and 40% O₂ + 30% CO₂ + 30% N₂) on the quality of fresh beef during subsequent storage at 4 °C. For this purpose, three separate experiments were performed. For each experiment, two different muscles (Longissimus dorsi and Biceps femoris) were sampled from four double‐muscled Belgian Blue beef carcasses. Next to colour, also the evolution in microbial load, pH, O₂ and CO₂ in the headspace and lipid oxidation at the meat surface were evaluated. A vacuum ageing for 14 days compared with 7 days resulted in a higher initial microbial load on the day of MAP packaging, which resulted finally in a significantly shorter shelf life. This ageing effect was less pronounced on the colour stability and lipid oxidation of the meat samples. No significant influence of the packaging configuration on any of the analysed parameters (colour, microbial load, pH and lipid oxidation at the meat surface) was observed.     

Microbiological and physicochemical properties of dry‐cured neck inoculated with probiotic of Bifidobacterium animalis ssp. lactis BB‐12

The effect of inoculum level of Bifidobacterium animalis ssp. lactis BB‐12 probiotic strain and ripening period on the quality of dry‐cured neck was studied. The microbiological parameters (Enterobacteriaceae, LAB and TVC) and physicochemical attributes (pH value, a_w, TBARS index, colour) were determined directly after fermentation at 15 °C for 3 weeks, after 6 and 12 months of ripening at 4 °C. The highest LAB count and a lower pH value were found in the meat inoculated with probiotic strain at 6.6 log cfu g^?1 (B2) followed by inoculation with probiotic strain at 6.3 log cfu g^?1 (B1). Level of inoculation had not had an influence on water activity, TBARS index and total colour parameters. Changes of fat oxidation during half‐year of ripening were limited in probiotic meat samples compared to naturally fermented control meat (C). Based on the results, it can be concluded that the most favourable physicochemical and microbiological parameters of the dry‐cured neck were obtained after 6 months of ripening. At that time, the Bifidobacterium BB‐12 at both levels is a good potential starter for meat fermentation.     

Effect of agitated bed drying on the retention of phenolic compounds,anthocyanins and antioxidant activity of roselle (Hibiscus sabdariffa L.)

An agitated fluidised bed dryer was employed to dry lixiviated roselle (Hibiscus sabdariffa L.) calyxes. The effects of operational drying variables on the chemical attributes such as the retention of monomeric anthocyanins (MA), phenolic compounds, polymeric colour, antioxidant activity and drying rate were analysed. Drying curves showed only decreasing falling rate period. To determine the kinetic parameters, the drying data were fitted to a Page's model, based on the moisture content ratio vs. the drying time; the k values ranged from 1.58 × 10^?5 to 6.28 × 10^?2 s^?1. The different drying conditions showed significant differences in the chemical parameters. When processing wet feeds, as lixiviated roselle calyxes, the mechanical assisted fluidisation can be considered as an innovative concept.