QUALITY CHANGES IN FRESH‐CUT SPINACH (SPINACIA OLERACEA) UNDER MODIFIED ATMOSPHERES WITH PERFORATIONS

ABSTRACT

Fresh‐cut spinach leaves were stored for 4 days at 15C and 75% relative humidity under modified atmosphere packaging to assess the impact of differential in‐pack gas atmospheres generated through different packaging films and variable in‐pack weight on the quality of stored produce. After 4 days of storage, retention of chlorophyll, β‐carotene and ascorbic acid was better in low‐density polyethylene (LDPE) packages than in polypropylene (PP) packages. LDPE film‐packaged samples had higher phenolic content than PP film‐packaged samples. Low in‐pack O₂ (1–2 kPa) along with the buildup of CO₂ (8–10 kPa) seems to have enhanced the retention of antioxidant components, i.e., β‐carotene and ascorbic acid, in LDPE packages. This helped in chlorophyll retention and also prevented formation of oxidation compounds of phenols that otherwise caused browning of cut surfaces. Thus, O₂ and CO₂ permeability of packaging film or in‐pack weight of produce might be such that equilibrated O₂ partial pressures remain near to 1–2 kPa so as to affect a beneficial increase in the phenolic content along with concomitant retention of chlorophyll.

PRACTICAL APPLICATIONS

Fresh‐cut spinach leaves have received an enormous demand due to their utility in various traditional Indian preparations. Shelf life and quality of fresh‐cut produce may be greatly reduced due to high rates of respiration. Traditional packaging and handling techniques reduce the shelf life and sensory quality of fresh‐cut spinach. Temperature control and atmospheric modifications help to maintain produce quality by reducing respiration rate and enhance shelf life by minimizing the adverse effects of cutting. This research focused on evaluation of respiratory behavior of fresh‐cut spinach leaves at a temperature commonly encountered during transportation and retail distribution, i.e., 15C, and the effect of different polymeric films and in‐pack weights on produce quality. The results of the study suggest that packaging of fresh‐cut spinach in polymeric film packages could maintain the sensory quality and reduce degradation of various physicochemical constituents. Utilization of the results for proper design of modified atmosphere packages for this highly perishable produce can prove to be extremely beneficial for safe storage and transportation to urban retail markets.     

Mesophilic Aerobic Population of Fresh-cut Spinach as Affected by Chemical Treatment and Type of Packaging Film

ABSTRACT: Fresh-cut spinach was treated with citric acid and ascorbic acid solutions and packaged in mono-oriented polypropylene bags or low-density polyethylene bags. Response surface methodology was used to study the simultaneous effect of chemical treatment and refrigerated storage time on headspace gas composition, mesophilic aerobic population (AP), and pH of fresh-cut spinach. Type of film affected %CO₂, %O₂, and pH but did not influence AP. Chemical treatment reduced initial pH values and initial microbial counts. AP and pH increased during refrigerated storage. The model developed for AP enabled finding acid concentrations that lowered AP below any proposed microbiological criterion at production and consumption stages of fresh-cut spinach stored at 4 °C.     

包装膜特性对菠菜品质的影响

探究不同特性PE膜包装对菠菜贮藏期间生理特征,营养价值以及感官品质的影响。采用4种不同特性的PE膜对菠菜进行包装,4±1℃条件下贮藏12 d,每隔3 d测定菠菜的袋内顶空气体组分、呼吸速率、失重率、腐烂率、颜色变化、叶绿素含量及VC含量的变化。采用主成分分析法对所测定指标进行综合分析。结果表明,PE3相对于其余3种不同膜特性的PE膜,可以明显降低失重率、腐烂率,较好的维持叶绿素含量和VC含量,可以很好地维持菠菜的品质。     

Internal quality and antioxidants content of cold-stored red sweet peppers as affected by polyethylene bag packaging and hot water treatment

Physical (weight, firmness) and compositional (sugars, organic acids, ascorbic acid, phenolic compounds and carotenoids) changes of red sweet peppers (Capsicum annuum L.) were monitored during 21 days of cold storage (at 7.5 °C); fruits were stored without packaging, packaged in low density polyethylene bags, or after hot water dipping (53 °C for 4 min) and packaging. Packaging prevented water loss, and preserved the firmness of the fresh product. Sugars (fructose and glucose) content was practically constant throughout the whole storage time, for all treatments. A moderate accumulation of citric acid was observed during storage, but no marked effects of packaging and hot water dipping on citric and malic acid content. Ascorbic acid content slightly increased in unpackaged and packaged fruits, but not in treated+packaged peppers. Hydroxycinnamics total content seemed not to be affected by cold storage, packaging or hot water treatment, whereas glycosylated flavonoids showed somewhat lowered levels during storage, particularly in the case of unpackaged and packaged+treated fruits. Regarding carotenoids content, the effect of the considered storage conditions seemed to be much smaller than that due to ripening stage. Provitamin A content showed an increasing trend in unpackaged and packaged fruits; packaged+treated peppers were characterised by a lower retention of provitamin A and a higher level of capsanthin and cucurbitaxanthin A with respect to not treated fruits. On the whole, packaging and hot water treatment did not produce noticeable adverse effects on the majority of the examined compositional quality parameters.     

Physical and chemical changes in minimally processed green asparagus during cold-storage

The purpose of this research is to study effects of an innovative packaging method on the shelf-life of minimally processed green asparagus. The physical–chemical parameters analyzed (weight loss, colour, texture, chlorophyll and citric acid), and monitored by untrained panellists during the cold storage period at 6 °C, showed that pairing of a semi-permeable film with an adsorbent material and immersion in ascorbic acid solution were able to extend the shelf-life of green asparagus. Also, on the basis of the results obtained, a study of the chlorophyll and toughness degradation kinetics of green asparagus was conducted during cold storage. These data showed the toughening of asparagus spears to be faster than chlorophyll degradation. Thus, the former can be used as a reliable quality index to predict the shelf life of such products.     

A comparative study on the effect of packaging material and storage environment on shelf life of fresh bell-pepper

The effect of packaging materials [low density polyethylene (LDPE), polypropylene (PP)] and storage environment [modified atmospheric packaging (MAP)] on shelf life enhancement of bell pepper in terms of quality attributes such as physiological weight loss, ascorbic acid, texture, surface colour and subjective quality analysis have been studied at ambient and refrigerated condition. Different packaging techniques used for the experiment were MAP with LDPE, MAP with PP, MAP in perforated LDPE films, MAP in perforated PP films, shrink packaging with bi-axially oriented PP (BOPP) film and vacuum packaging with PP film. The in-pack bell pepper created a suitable headspace environment with low O₂ and high CO₂ concentrations, which resulted in a better retention of freshness of the vegetables and its marketability. Shrink packaging with BOPP film could not yield better result under ambient storage because of high water vapor transmission rate of the film and consequently loss of turgidity of the vegetables. Among different packaging techniques and storage conditions, MAP with PP film in refrigerated condition was found to be the best followed by vacuum pack with PP film in refrigerated condition and could be used to store for 20 days for bell pepper with maintenance of texture, colour, ascorbic acid and marketability. It is also inferred that under ambient conditions, bell pepper could be stored for 4 days using ventilated LDPE and PP as MAP storage. Further studies are needed to evaluate the sensory aspects, as well as to microbiological evaluation to characterize the fresh bell pepper during storage.     

Changes in post-harvest phytochemical qualities of broccoli florets during ambient and refrigerated storage

The effect of ambient and refrigerated storage temperature on post-harvest phytochemical qualities of broccoli florets was investigated during storage. Fresh broccoli florets were packed in polypropylene (PP) micro-perforated film bags and stored, under open ambient storage conditions (15 ± 1 °C, 55 ± 2% RH), and laboratory refrigerated storage (4 ± 0.5 °C, 50 ± 2% RH) for a total period of 144 h. Quality of broccoli florets was evaluated in terms of physiological weight loss (PLW), ascorbic acid content, chlorophyll content, β-carotene and total antioxidant activity. Samples packed in PP micro-perforated film showed significantly (P < 0.05) lower losses of PLW, ascorbic acid, chlorophyll, β-carotene and total antioxidant activity (5.51%, 4.53%, 18.9%, 4.04% and 16.4%, respectively), during storage for up to 144 h under refrigerated conditions. For better phytochemical retention, the broccoli florets should be packed in PP micro-perforated film bags and stored under refrigerated conditions.     

Retail Shelf-Life of Pork Dipped in Organic Acid before Modified Atmosphere or Vacuum Packaging

Modified atmosphere packaging (MAP) is increasingly popular for meat, but raw, chilled pork in vacuum or anoxic environments has a purple color. The retail shelf‐life of pork chops dipped in 500 ppm ascorbic acid, 250 ppm citric acid, or no acid dip and stored at 1 °C before simulated retail display in MAP with gas exchange or air‐permeable packaging after vacuum pouch storage was determined. The 80% N₂:20% CO₂ in MAP was exchanged with 80% O₂:20% CO₂, and chops were removed from vacuum packages and overwrapped with permeable film (VP‐PVC) on the 7th day before simulated retail display at 4 °C. Shelf‐life traits were determined at 1, 7, 8, 10, 12, and 14 d postpackaging. The pH values changed with time, but returned to post‐dipped, prepackaged levels at the end of simulated retail storage. Weight loss of chops increased (P < 0.05) in VP‐PVC compared with MAP. The a* values increased (P < 0.05) and L* and b* values decreased during simulated retail display, with higher L*, a*, and b* color values for chops in MAP than VP‐PVC. Log numbers of psychrotrophic microorganisms were higher (P < 0.05) on VP‐PVC samples than for chops in MAP on days 12 and 14. Psychrotrophic counts on ascorbic acid‐treated samples were decreased compared with citric acid or no dipping on pork during simulated retail display. Pork chops in MAP with gas exchange had lighter and redder color, increased weight retention, decreased psychrotrophic counts, and increased lipid oxidation compared with conventional vacuum and overwrap packaging systems.     

Effect of film and temperature on the sensory, microbiological and nutritional quality of minimally processed cauliflower

The effect of atmosphere modification, generated using three different packaging films, on the quality of cauliflower minimally processed when stored at 4 or 8 °C for up 20 days was evaluated. The colour, texture, weight loss, sensory attributes, as well as microbial counts and sugars and ascorbic acid content were determined. The atmosphere generated with the perforated polyvinylchloride (PVC) film was hardly modified, whereas the other two films (non-perforated PVC and polypropylene films) originated changes in CO₂ and O₂ levels during storage. The different packaging conditions and storage temperature influenced yellowing. An increase in shear force was observed. Weight losses were below 5%. Mesophiles and Pseudomonas counts were below 7 log CFU g⁻¹, the populations being lower with film B and film C than with film A. Cauliflower maintained an acceptable appearance in all the films studied. Total sugars decreased about 27% after 20 days of storage, whereas ascorbic acid did not change.     

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.     

Optimization of Temperature,Relative Humidity and Storage Time before and after Packaging of Baby Spinach Leaves Using Response Surface Methodology

Second-order polynomial models were used to relate the independent variables, temperature, relative humidity and storage time, to the quality attributes (electrolyte leakage, chlorophylls, weight loss, humidity and headspace gas composition inside packages before and after packaging) of ready-to-eat spinach leaves. Results show that while waiting for processing the best conditions to assure high quality spinach leaves before packaging were 4 °C, 83 % RH and 4 h. The weight loss of spinach leaves was time-dependent: increasing the exposure time under these conditions decreased the amount of wet leaves before packaging. Under the same conditions, the electrolyte leakage was lower (4.63 %) and the chlorophyll content (45.44) was higher. After packaging and while waiting for dispatch, temperature most affected the package headspace atmosphere. Indeed, an increase in storage temperature from 3 to 7 °C led to a significant increase in respiration. The best combination of conditions in the high-care room was 3 °C, 74 % relative humidity for a maximum of 1 day before dispatch. In this case, the moisture content (0.46 %) and electrolyte leakage (4.16 %) were lower and the chlorophyll content (43.37) and oxygen concentration inside the packages of ready-to-eat spinach leaves (19.55 kPa) were higher.     

Quality of Green Beans, Bell Peppers and Spinach Stored in Polyethylene Bags

Quality attributes of packaged and unpackaged vegetables generally decreased nonlinearly during storage at 10°C or 20°C, and most of the decrease was greater at 20°C than at 10°C. Packaging reduced weight loss of green beans and spinach kept at 20°C; and reduced chlorophyll loss of green beans at 10°C and of spinach at 20°C. Ascorbic acid (vitamin C) benefited by packaging of green beans and spinach kept at 10°C. Packaging had an effect on thiamin (vitamin B₁) of only spinach held at 10°C and 20°C and had no effect on riboflavin (vitamin B₂). Loss of these quality attributes appears to be enhanced with water loss.     

鲜切青笋防腐保鲜工艺的优化及不同包装材料对其品质的影响

为了研究不同防腐剂和不同包装材料对鲜切青笋防腐保鲜的效果,并延长其贮藏时间,通过预试验选择山梨酸钾、纳他霉素、柠檬酸为有效合适的防腐剂,按照L9(34)正交试验制作不同配比的防腐保鲜复合液,以鲜切青笋在贮藏过程中的细菌总数、失重率及硬度为测定指标,最终以综合评分确定最佳复合液配比。结果表明:防腐保鲜液的最佳配比为0.02%纳他霉素+2.0%柠檬酸+0.04%山梨酸钾。以普通塑料薄膜保鲜袋作对照,研究不同规格(0.07 mm、0.08 mm、0.09 mm)透气性的双向拉伸尼龙(BOPA)与低密度聚乙烯(LDPE)复合包装袋对鲜切青笋包装储藏期间的失重率、维生素C的含量、硬度的影响,并选择最佳的包装材料。结果表明:0.07 mm规格的复合材料包装鲜切青笋效果最佳。     

QUALITY OF MINIMALLY PROCESSED LETTUCE AS INFLUENCED BY PACKAGING AND CHEMICAL TREATMENT

Shredded lettuce was packaged in sealed bags of monooriented polypropylene (OPP) film and also in polyethylene (PE) trays overwrapped with a multilayer polyolefin (RD106) or plasticized polyvinyl chloride (PVC) film; and stored at 4C in a refrigerated case during 8 days. Chemical treatment by dipping in a 0.3% ascorbic acid /0.3% citric acid solution did not significantly affect changes in microbial populations or visual sensory attributes. Type of package was not a significant factor for microorganism populations, but was significant (p<0.001) for changes in gas composition and visual sensory attributes. The modified atmosphere within the packages changed from normal air composition to about 1.5% O₂/12% CO₂ for OPP bags and to about 17–18% O₂/1–2% CO₂ for PVC-PE trays and RD106-PE trays after 8 days of storage. The visual sensory quality of the product was retained better in OPP bags than in the other ones.     

Effect of low‐cost storage and packaging on quality and nutritive value of fresh and dehydrated carrots

Fresh carrots (Daucus carota L cv ‘Nantes’) were packed in Netlon and ventilated low‐density polyethylene bags and stored in ambient, cool chamber and cool store conditions. Blanching and drying conditions were standardised and the sliced carrots were dehydrated to 7–9% moisture content using the best blanching and drying combination. Dehydrated carrots were packed in single and double layers of high‐density polyethylene bags and stored in ambient and cool store conditions for 9 months. The shelf‐life of fresh carrots varied from 3 to 20 days depending on the packaging and storage condition. A reduction in β‐carotene and ascorbic acid content and an increase in electrolyte leakage were observed during storage of fresh carrots. Blanching and drying caused a significant reduction in β‐carotene and ascorbic acid content, which further decreased during storage of dried product. The storage study of dried product showed that retention of β‐carotene and ascorbic acid was better in double‐packed and cool‐stored samples, and it also showed minimum browning during storage. © 2000 Society of Chemical Industry     

EFFECT OF PACKAGING MATERIAL ON THE QUALITY OF POTATOES TREATED WITH ISOPROPYL N-(3-CHLOROPHENYL) CARBAMATE (CIPC)

Katahdin and Russet Burbank potatoes, treated with isopropyl N-3(-chlorophenl) carbamate CIPC and stored for four months at 5C in either mesh or polyethylene bags (two packaging materials frequently used for potato storage), were tested for enzymatic discoloration, phenolic and ascorbic acid concentration. CIPC residues in tubers stored in polyethylene bags were significantly (p < 0.0l) higher than those stored in mesh bags. Tubers stored in polyethylene showed significantly (p<0.05) higher discoloration and phenolic concentration, and lower ascorbic acid concentration than those stored in mesh bags. Differences in CIPC retention of the tubers stored in the two packaging materials may have been responsible for some of the differences in quality factors since CIPC was shown to significantly (p<0.0l) increase the enzymatic discoloration and phenolic concentration, and decrease the ascorbic acid concentration of both cultivars.     

Biochemical,microbiological and sensory changes in shrimp (Panaeus aztecus) dipped in different solutions using face‐centred central composite design

Biochemical, microbiological and sensory changes during shelf‐life at ?1 °C were determined in shrimp (Panaeus aztecus) previously dipped in ascorbic acid, citric acid, potassium sorbate and 4‐hexyl resorcinol solutions using face‐centred central composite design. Microbiological count, trimethylamine and hypoxantine production were measured. The lowest level of the total psychrotrophic bacteria, hypoxantine and trimethylamine were found in samples dipped in all containing chemicals solutions comparing to control treatment. Sensory studies showed that treatment A (ascorbic acid 4.50, citric acid 0.12, potassium sorbate 18.60 and 4‐hexyl resorcinol 0.25, all g L^?1) and B (ascorbic acid 4.37, citric acid 1.26, potassium sorbate 7.03 and 4‐hexyl resorcinol 0.25, all g L^?1) did not alter the typical sensory features of shrimp and were effective at delaying the bitter off‐flavour formation for 26 days. This study constitutes a promising alternative to extent shelf‐life of shrimp kept at ?1 °C without freezing.     

贮藏温度和包装材料对百合保鲜包装品质的影响

采用不同贮藏温度(30℃和5℃)和包装材料(PE、OPP、OPP/PE膜)对百合进行保鲜包装,测定不同贮藏时间下的百合球茎Vc含量、总糖含量、色差、失重率和感官品质变化。结果表明:低温能够显著抑制百合失重,保持其较好的色泽和总糖含量。不同包装材料比较,具有较高透气率的PE、OPP膜保鲜效果较好,OPP/PE膜次之。低温与包装之间有较好的协同作用。