Combined high pressure-mild temperature processing for optimal retention of physical and nutritional quality of strawberries (Fragaria × ananassa)

Response surface methodology was used to determine the optimal high pressure-temperature condition for the processing of strawberries for maximal inactivation of oxidative enzymes as well as best retention of nutritional and physicochemical quality following processing and during storage. High pressure treatment at 20–40 °C resulted in visual quality closest to the fresh product. High pressure combined with mild temperature caused substantial inactivation of peroxidase in strawberries with a maximum of 58% inactivation after 10 min treatment at 600 MPa and 60 °C. No significant inactivation of polyphenol oxidase was observed in strawberries under the studied condition. Combined high pressure-mild temperature processing did not have significant effect on the total polyphenol and total anthocyanin content of strawberries. However, an average of 22 ± 13% loss of total polyphenol content and 27 ± 10% loss of total anthocyanin contents was observed after 3 months of refrigerated storage.Industrial relevanceThe work described in this research is relevant to the high pressure processing of strawberries and other berry fruits. The results of the study have shown that best quality retention of strawberry products is obtained when high pressure processing is combined with vacuum packaging in high barrier packaging material and refrigerated storage since strawberry polyphenol oxidase is highly resistant to high pressure inactivation.     

冰箱气调贮藏对水果的保鲜效果

为研究冰箱（5℃）气调贮藏对水果保鲜效果的影响,本研究选取了四种水果车厘子、草莓、红元帅苹果、蓝莓,在对照冰箱（常氧21%）和气调冰箱（O₂含量18~18.5%）中冷藏7 d,通过测定贮藏期间失重率、维生素C含量、花青素含量及果实表层细胞形态来检测气调冰箱的保鲜效果。结果表明：冰箱低温气调贮藏的四种水果保鲜效果最好,均能够显著（P<0.05）降低失重率,提高维生素C和花青素的保留率,改善果实的表观品质,减缓水果的感官品质劣变,维持水果的新鲜度,并维持水果良好的表皮细胞形态。因此,冰箱低温气调贮藏更有利于水果的保鲜。     

Fluctuations in the Levels of Antioxidant Compounds and Antioxidant Capacity of Ten Small Fruits During One Year of Frozen Storage

The fluctuations in antioxidant capacity (2,2-diphenyl-1-picrylhydrazyl, 2,2´-azinobis (3-ethylbenzthiazoline-6-sulphonic acid), and ferric reducing/antioxidant power assays), total phenol, total flavonoid, and total anthocyanin contents of 10 small fruits (sweet cherries, sour cherries, strawberries, red currants, raspberries, blackberries, hawthorn, cornelian cherries, and red and white grapes) were monitored during storage at ?20°C. After one year in storage, all varieties except hawthorn and white grapes retained equal or slightly greater total phenol content in comparison to the initial values. The total flavonoid and total anthocyanin levels also remained stable or even increased after 12 months in all fruits exept hawthorn and strawberries. Red currants and raspberries exhibited optimal preservation of antioxidant capacity, while hawthorn showed a decrease in the antioxidant capacity during different time points in storage as well as at the end of storage. Analyzed fruits were classified into four main groups based on hierarchical cluster analysis.     

Influence of nano-ZnO on microbial growth,bioactive content and postharvest quality of strawberries during storage

A rapid decline of quality causes economic loss of strawberries after harvest. Treatments based on nano-ZnO at different concentrations (0.03%, 0.07% and 0.5%) were used to prolong the shelf-life of strawberry fruit in cold storage. After treatments microbial growth, weight loss, firmness, titratable acidity, soluble solid content, pH value, vitamin C, anthocyanin and total phenolics and antioxidant activity were evaluated at 0, 3, 6, 9, 12, 15 and 18 days of storage. Furthermore, the levels of zinc and the sensory attributes of treated strawberries were evaluated three days after treatment. Nano-ZnO treatments decreased the microbial load during fruit storage (total mesophilic bacteria in control and 0.5% nano-ZnO treated strawberries were 4.35 and 3.67 Log CFU g^− 1, respectively). Treatments delayed weight loss, retained fruit firmness and maintained anthocyanin, vitamin C, phenol content and antioxidant activity at higher concentration than those of untreated fruit. Fruit sweetness and aftertaste attributes were not affected by treatments but the 0.5% ZnO treated fruit was less luminous (1.6) compared to control (5.6). 0.5% nano-ZnO was the most effective in delaying changes in the ripening and reducing microbial populations among the treatments. These findings indicated that the nano-ZnO might provide an alternative to maintain quality and control decay of fresh strawberries during extended storage.Industrial relevanceStrawberries are a highly perishable fruit and postharvest life is limited to 4 days or even shorter at room temperature or 2 weeks at cold storage, therefore finding a method to extend the shelf life of strawberries is important. Modified atmosphere packaging is a useful method but control of spoilage microorganisms is still a problem. Fruit coating has great potential to extend fruit postharvest life and maintain nutritional quality. Nano-ZnO may be an effective alternative.     

Quality of fresh‐cut purple‐fleshed sweet potatoes after X‐ray irradiation treatment and refrigerated storage

The effect of X‐ray irradiation on the quality of fresh‐cut, refrigerated purple‐fleshed sweet potato (PFSP) cubes was investigated. Packaged sweet potato cubes were treated with 0, 250, 500, 750 or 1000 Gy X‐ray irradiation and stored at 4 ± 1 °C for 14 days. After 14 days, total aerobic bacteria counts were 4.1 and 3.2 log₁₀ CFU g^?1, and mould–yeast counts were 3.3 and 3.0 log₁₀ CFU g^?1 in 750 and 1000 Gy treated samples, respectively. Doses up to 1000 Gy did not affect the firmness, moisture content and anthocyanin content of PFSP cubes throughout storage. PFSP cubes' flesh colour did not change during the first week of storage, but lightness (L*) increased after 14 days. Also, irradiation doses at 750 and 1000 Gy decreased saturation (C*) significantly, producing duller flesh colour than controls. Results indicate that X‐ray irradiation treatment at doses up to 1000 Gy can reduce microbial populations while maintaining the physical quality and anthocyanin content of PFSP cubes up to 14 days of storage.     

Losses of vitamin C from fresh strawberries in a commercial supply chain

Fresh strawberries were evaluated through a commercial supply chain, from harvest to immediately prior to retail display. These samples were compared with controls that were refrigerated immediately after harvest and kept at a constant temperature for the same period of time. Temperature data were collected throughout all stages of the supply chain. Moisture and vitamin C (ascorbic acid) contents were determined at selected points of the supply chain using recognised methodology. Significant differences were found in the vitamin C concentrations of fresh strawberries at various stages of the supply chain but not in their moisture content. The ascorbic acid concentration decreased with time spent in the supply chain in all trials but the absolute vitamin C content differed from trial to trial. This result indicates that both pre- and post-harvest factors influence the vitamin C content of fresh strawberries available to consumers on the retail market.     

Effect of refrigerated storage on vitamin C and antioxidant activity of orange juice processed by high-pressure or pulsed electric fields with regard to low pasteurization

A better knowledge of the effect of refrigerated storage on the nutritional and antioxidant characteristics of foods processed by emerging technologies with regard to thermal traditional technology is necessary. Thus, freshly squeezed orange juice was processed by high-pressure (HP) (400 MPa/40 °C/1 min), pulsed electric fields (PEF) (35 kV/cm/750 μs) and low pasteurization (LPT) (70 °C/30 s). The stability of vitamin C and antioxidant activity was studied just after treatment and during 40 days of refrigerated storage at 4 °C. The determination of total vitamin C (ascorbic acid plus dehydroascorbic acid) was achieved by HPLC whereas the antioxidant activity was assessed by the measurement of the DPPH• radical scavenging. Just after treatment, all treated orange juices showed a decrease lower than 8% in vitamin C content compared with the untreated one. At the end of refrigerated storage, HP and LPT juices showed similar vitamin C losses (14 and 18%, respectively) in relation to untreated juice, although HP juices maintained better the vitamin C content during more days than LPT juices. Regarding antioxidant activity, after 40 days at 4 °C, differences among treated juices were no significant in terms of antiradical efficiency (AE=1/EC₅₀T_EC50). HP and PEF may be technologies as effective as LPT to retain antioxidant characteristics of orange juice during refrigerated storage.     

Effects of chitosan coating on shelf life of cold-stored litchi fruit at ambient temperature

Postharvest pericarp browning of litchi fruit results in an accelerated loss in shelf life and a reduced commercial value. Visual quality was lost in only 6 h at ambient temperature when fruit were removed from storage at 2 °C, due to browning. The experiment was conducted to test the role of chitosan coating in inhibiting skin browning and extending shelf life of cold-stored litchi fruit at ambient temperature. Litchi fruit were treated with 2 g chitosan/100 g solution and then stored for 20 days at 2 °C and 90–95% relative humidity (RH), prior to shelf life evaluation at 25 °C and 80–90% RH. Changes in polyphenol oxidase (PPO) activity, anthocyanin concentration, colour index, eating quality and concentrations of total soluble solids and titratable acidity were measured. The effects of chitosan coating on disease incidence were also evaluated. Application of chitosan coating delayed the decrease in anthocyanin content, the increase in PPO activity and the changes in colour index and eating quality, reduced the decrease in concentrations of total soluble solids and titratable acidity, and partially inhibited decay. The results suggested that treatment with chitosan coating exhibited a potential for shelf life extension at ambient temperature when litchi fruit were removed from cold storage.     

Effect of thermal treatment and storage on the stability of organic acids and the functional value of grapefruit juice

The effect of conventional and microwave pasteurisation on the main bioactive compounds of grapefruit juice and their stability during 2 months’ refrigerated and frozen storage was evaluated. Ascorbic acid (AA), vitamin C and organic acids were analysed by HPLC, whereas total phenols and antioxidant capacity (%DPPH) were measured by spectrophotometry. The results showed that conventional treatment led to a significant decrease in citric acid (from 1538 to 1478 mg/100 g) and AA (from 36 to 34.3 mg/100 g), whilst microwave pasteurisation preserved these compounds. Frozen storage maintained AA and vitamin C, especially in treated samples. Frozen non-treated samples and conventional pasteurised ones preserved about a 75% and 20% of the total phenols and antioxidant capacity, respectively, whilst in frozen microwave pasteurised juices this preservation was of 82% and 33%. From these results, the use of microwave energy may be proposed as an alternative to traditional heat pasteurisation in order to preserve the natural organoleptic characteristics and essential thermolabile nutrients of grapefruit juice.     

Effect of high hydrostatic pressure and thermal processing on the nutritional quality and enzyme activity of fruit smoothies

Fruit smoothie samples were thermally (P₇₀ > 10 min) or high hydrostatic pressure (HHP) processed (450 MPa/20 °C/5 min or 600 MPa/20 °C/10 min) and the total antioxidant capacity (TAC), levels of antioxidant groups [total phenols (TP), anthocyanins and ascorbic acid], instrumental colour, polyphenol oxidase (PPO) enzyme activity and dissolved oxygen were examined over a storage period of 10 h at 4 °C. Thermal processing of smoothies reduced (p < 0.001) TAC and TP values, ascorbic acid and L and a colour attributes (lightness and redness respectively) compared to fresh and HHP-450 processed samples. Conversely, it did result in complete inactivation of PPO enzyme, with no activity detected. Of the HHP treatments, HHP-450 samples had higher (p < 0.001) levels of total antioxidant, phenols and anthocyanin content than HHP-600 samples. However, the latter was more effective in reducing (p < 0.001) the endogenous enzyme activity of the smoothies. .Ascorbic acid content degraded over the storage for all smoothies. HHP-600 samples had high initial values, which declined slowly over storage, while thermal samples had the lowest initial value (0.5 h) that fell below detectable limits by 10 h. Despite these data, less pronounced effects were observed for storage. No significant effects were observed for total anthocyanin and phenolic contents as well as L and colour change (ΔE) variables. Overall, HHP processing of smoothies at moderate temperatures may be a suitable alternative to traditional thermal processing.     

Changes in phytosterol contents during rape seed storage under conditions simulating industrial silos

During seed storage in tall silos the low layers of rape seeds are exposed to static pressure exerted by the upper layers. This may cause deformation and damage of seeds found in the lower layers and losses of biologically active compounds. The aim of this study was to simulate under laboratory conditions the actual ecosystem found in industrial plants and to evaluate the effect of not only the temperature and moisture content, but also static pressure on degradation of phytosterols contained in rape seeds in the course of storage. Changes in phytosterol levels were assessed using GC-MS. During storage in all samples of seeds (7–16% moisture content) under the adopted conditions of overpressure (20–60 kPa) and temperature (25–35 °C) the total content of phytosterols decreased by 3–57%. The smallest losses in the total phytosterol contents (3–4%) were recorded during storage of seeds with a 7% moisture content, irrespective of the applied storage temperature (25–35 °C) and overpressure variants (20–60 kPa). The greatest losses of phytosterols (43–57%) were observed during storage of seeds with a 16% moisture content at a temperature of 35 °C, while the higher the applied overpressure, the greater these losses were. The study showed that the greatest influence on sterol content during storage was increased seed moisture, and subsequently the temperature and the pressure. Experimental results also showed that for seeds with higher moisture contents (13 and 16%) an increase in storage temperature from 30 to 35 °C intensifies losses of individual phytosterols much more markedly that an increase in temperature from 25 to 30 °C. Moreover it was observed that overpressure over 20 kPa enhanced losses of investigated phytosterols.     

The impact of delactosed whey permeate treatment on shelf‐life and antioxidant contents of strawberries

The aim of this study was to investigate the effect of delactosed whey permeate (DWP) treatment on antioxidant and physicochemical properties of strawberries. Fresh strawberries treated with 3% DWP were analysed for different quality, nutritional and microbiological markers during 10 days of storage at 5 °C. The results showed that DWP treatment significantly reduced incidences of decay (70%) and numbers of total aerobic counts (～1.4 Log₁₀ CFU g^?1) and yeast and moulds (～1.8 Log₁₀ CFU g^?1). DWP treatment also inhibited the loss of firmness (15%) and maintained significantly (P ≤ 0.05) higher levels of vitamin C, total phenols and antioxidant activity of strawberries. Sensory scores confirmed that the DWP‐treated strawberries retained a good appearance and overall quality. The aroma and colour attributes were not reduced during storage. These results suggest that DWP treatment has potential to extend the shelf‐life and maintain the quality of strawberries during storage.     

Effects of traditional and modified technology,in the production of frozen cauliflower,on the contents of selected antioxidative compounds

The investigation concerned white and green cauliflowers: a traditional technology of freeze – blanched cauliflower, a modified technology of freeze – cooked cauliflower, and two temperatures of frozen storage at −20 and −30 °C for 0, 4, 8, and 12 months. Compared with the white cauliflower, the green variety was characterized by significantly greater contents of dry matter, vitamin C, carotenoids, β-carotene, polyphenols and a higher antioxidative activity at all the stages of evaluation. Depending on the investigated sample, after 12 months of refrigerated storage, cauliflower prepared for consumption retained 29–50% of vitamin C, 73–100% of carotenoids, 53–125% of β-carotene, 69–85% of polyphenols and 26–40% of antioxidative activity in comparison with the raw material. After a 12-month storage, the product obtained using the modified technology contained significantly more vitamin C and in general showed a higher antioxidative activity than did with the traditional product. The lower storage temperature resulted in significantly better retention of vitamin C and also – in some samples – a better retention of carotenoids, β-carotene, and polyphenols. A higher sensory quality was found in products of green cauliflower obtained according to the traditional technology.     

Effects of Antimicrobial Edible Coating of Thymol Nanoemulsion/Quinoa Protein/Chitosan on the Safety,Sensorial Properties,and Quality of Refrigerated Strawberries (<Emphasis Type="Italic">Fragaria × ananassa</Emphasis>) Under Commercial Storage Environment

The effectiveness of the edible coating with thymol nanoemulsion on the safety, sensorial properties, and quality of refrigerated strawberries was investigated under commercial storage conditions. Spontaneous emulsification was used to obtain the thymol nanoemulsion that was included on quinoa protein/chitosan coatings. During the entire storage time, strawberries coated with thymol-antimicrobial packaging had a lower fungal and yeast load compared with the controls (uncoated and coated with quinoa protein/chitosan). The flavour and aroma of the coated strawberries was initially affected, although this sensory appreciation was improved from the fifth day of storage and showed similar scores than the controls, and presenting better aroma score at day 12 of storage. Furthermore, the shelf life of the thymol nanoemulsion-coated strawberries increased in 4 days, unlike that in the both controls. Further, the application of these biocoatings on strawberries significantly decreased the weight loss relative to that in the control, during 16 days of storage at 5 °C and 90% relative humidity, and did not alter the quality parameters (pH, titrable acidity, and percentage of soluble solids). These results suggest that the application of thymol/nanomulsion-loaded edible films is an effective strategy to increase the shelf life of highly perishable products such as strawberries.     

南极磷虾壳聚糖、壳寡糖的制备与品质鉴定

本研究以南极磷虾壳为原料,制备较高品质的壳聚糖与壳寡糖,并对二者的品质进行鉴定。南极磷虾壳经脱钙、脱蛋白处理,探索脱乙酰反应条件（碱溶液浓度、反应温度与反应时间）,制备具有较高脱乙酰度的南极磷虾壳聚糖,并对壳聚糖的理化指标进行鉴定;探索酶法降解条件（壳聚糖酶添加量、酶解时间）,制备较高纯度的南极磷虾壳寡糖,并对壳寡糖的结构特征进行鉴定。结果表明,使用60%的氢氧化钠于110 ℃脱乙酰处理4 h制备的南极磷虾壳聚糖脱乙酰度为85.74%,粘均分子量为 305.65 kDa,水分含量4.66%,灰分含量0.98%,酸不溶物含量0.40%,各项理化指标均符合食品级壳聚糖的要求;使用壳聚糖酶水解南极磷虾壳聚糖制备壳寡糖,在壳聚糖酶添加量为0.2% （m/V）,酶解16 h条件下,南极磷虾壳寡糖产品得率为46.0%,红外光谱与NMR谱图显示了表征壳寡糖结构的全部特征峰,质谱结果显示南极磷虾壳寡糖主要由二糖(GlcN)₂、三糖(GlcN)₂-GlcNAc与四糖(GlcN)₃-GlcNAc构成。本研究通过制备较高品质的壳聚糖与壳寡糖,为南极磷虾壳的高值综合利用与南极磷虾新产品开发提供了技术支持。     

Antioxidant stability of small fruits in postharvest storage at room and refrigerator temperatures

Strawberries (Fragaria ananassa), raspberries (Rubus idaeus) and red currants (Ribes rubrum), as well as two drupes, cherries (Prunus avium), and sour cherries (Prunus cerasus), were subjected to two storage temperatures (4 °C and 25 °C) and phytochemicals concentrations (total phenols, flavonoids and anthocyanins) as well as antioxidant capacity (DPPH, ABTS and FRAP assays) were monitored until the fruit visually spoiled. Red currants and strawberries exhibited the highest initial total phenol (TP) contents (322.40 ± 5.56 and 335.47 ± 6.12 mg GAE/100 g FW, respectively) and maintained the highest TP contents throughout storage at both temperatures. Storage of at 25 °C as opposed to 4 °C, facilitated faster spoilage of analyzed fruits. In addition, most fruits stored at 4 °C, exhibited slightly higher antioxidant activity values at the end of storage according to all three antioxidant activity assays as opposed to fruits stored at 25 °C. The dynamic evolution of antioxidant capacity at both temperatures reflected the transient changes in phytochemical composition of small fruits in storage.     

Active chitosan–chestnut extract films used for packaging and storage of fresh pasta

A tannins-rich chestnut extract was used to enhance the antioxidant and antibacterial properties of chitosan-based film materials. The favourable mechanical properties of the novel material enabled its application in the preparation of the sachets that were used for packing and storage of filled fresh pasta. The fresh pasta ageing progressed in conventional refrigerated storage conditions of 8 °C with 60 ± 2% relative humidity in the absence of light for 60 days. The rapid moisture mobility between a starchy food and sachets during the first 9 days of storage induced retrogradation of the fresh pasta, whereby total phenolic content show dependency on moisture throughout the shelf life. Active components within the sachet prevented microbial growth on the food surface during the entire 60 days.     

Effect of cold atmospheric plasma and pulsed electromagnetic fields on strawberry quality and shelf-life

The effect of cold atmospheric plasma (CAP) and pulsed electromagnetic fields (PEMF) on the metabolic process, microbiological, enzymatic and quality parameters of fresh strawberries, after processing and during storage at 1 and 6 °C, was studied. CAP was more effective on microorganisms, reducing the total viable count by ~0.9 logCFU/g. Phenolic compounds and antioxidant activity were increased after CAP processing by ~20.9 and 16.5%, respectively. PEMF strawberries were firmless by ~16% compared to control. Both treatments did not significantly affect the weight loss, color, anthocyanins content and pH-value. B-glucosidase activity was higher for PEMF strawberries by at least 35 and 20%, compared to control and CAP respectively, explaining PEMF enhancing aromatic-profile. Ascorbic acid was decreased during storage, nevertheless, nonthermal treated samples showed higher values by at least 10%, compared to control samples. The shelf-life at 1 °C for control, CAP and PEMF strawberries was estimated as 13, 17 and 15 days, respectively.     

Carotenoid and flavanone content during refrigerated storage of orange juice processed by high-pressure, pulsed electric fields and low pasteurization

The impact of different processing technologies, including non-thermal technologies, on bioactive compounds of orange juice was investigated. Freshly squeezed orange juice was treated by high pressure (HP) (400 MPa/40 °C/1 min), pulsed electric fields (PEF) (35 kV cm⁻¹/750 μs) and low pasteurization (LPT) (70 °C/30 s). The stability of main carotenoids and flavanones was studied just after treatment and during 40 days of refrigerated storage at 4 °C. Just after treatment, HP juice showed a significant increase on total carotenoid and flavanone content extracted (45.19 and 15.46%, respectively) and on vitamin A value (30.89%) with regard untreated juice, whereas no significant changes were observed for PEF and LPT juices. For all treated orange juices, flavanone content decreased significantly (around 50%) during the first 20 days of storage at 4 °C while carotenoid content showed a moderate decrease (less than 11%) that took place during the last 20 days. In general, during refrigerated storage, carotenoids and flavanones remained higher in HP juice than in LPT and PEF juices. Hence, HP and PEF technologies were as effective o even more than LPT to preserve bioactive compounds in orange juice during refrigerated storage.