| 1. |
- Ahrné, Lilia, et al.
(författare)
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Improvement of texture by modifying processing conditions
- 2003
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Ingår i: Acta Hortic.. - : International Society for Horticultural Science. - 9789066059764 ; 604, s. 277-277
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Konferensbidrag (refereegranskat)abstract
- Fruit and vegetable processors, faced with the challenge of gaining and maintaining a healthy position in the competitive fruit and vegetable sector, are optimising traditional processes towards product quality. Using frozen potatoes as a case study, the aim of this study was to evaluate the potential of improving the texture of potatoes by modifying the processing conditions. The texture of processed frozen potatoes is the result of the integral effect of the unit operations applied through the production chain. Production of frozen potatoes includes a blanching, a freezing, thawing/cooking step before being served. In this study, blanching temperatures from 70 to 97 °C up to 10 minutes were tested and combined with freezing by two freezing methods, impingement and air-blast freezing. The texture was measured after cooking of frozen potatoes in boiling water. Besides texture, water holding capacity, microstructural evaluation and pectinmethylesterase (PME) activity were determined. Blanching of potatoes prior to freezing can both improve water holding capacity and texture of potatoes, but this effect depends on the freezing rate and blanching temperature. Potatoes frozen with fastest freezing method are firmer and hold more water than the ones frozen by air-blast freezing. Blanching at 70 °C can lead to potatoes that after cooking retain a firmer texture, compared with blanching at 90 °C. The duration of the blanching treatment has also an important effect on texture changes. The studies of PME activity showed a good correlation between texture and PME for blanching at 90 °C, but for blanching at 70°C and longer times, the development of texture does not seem to be solely related to PME activity. Microstructural studies showed that the differences in texture are due to differences in the degree of starch gelatinisation and integrity of the cellular structure.
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| 2. |
- Ahrné, Lilia, et al.
(författare)
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Modelling textural changes of vegetables during acidification under isothermal and non-isothermal conditions
- 2001
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Ingår i: Acta Horticulturae. - 0567-7572. ; 566, s. 323-328
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Tidskriftsartikel (refereegranskat)abstract
- Acidification can be used to improve the quality of canned vegetables because it can decrease thermal processing requirements. Moreover, there is some evidence that acidified vegetables retain a better texture than non-acidified ones. Optimisation of the acidification processes requires the knowledge of the relationship between texture and thermal process at low/moderate temperature. The main objective of this work was the modelling of textural changes of vegetables during acidification under isothermal conditions, and the application of the model to predict textural changes in non-isothermal processes. Turnip was the vegetable used in the experiments. The effect of pre-treatments (blanching, freezing/thawing, calcium addition and vacuum infusion of water before acidification) on the kinetics of textural changes during acidification was also studied. Turnips were acidified in acetic acid under isothermal (20, 50, 70, 80, 90 and 100°C) and non-isothermal conditions (20 to 90°C). Texture was modelled by a two subtract first order kinetic model, assuming an Arrhenius-type dependence of the rate constants on temperature. The model parameters were estimated by nonlinear regression. At temperatures lower then 70°C no significant changes in texture were detected. At higher temperatures the model showed a good fit to the data for all the conditions tested. Acidification decreased the percentage of heat labile substrate from 96% to 62%, thus improving firmness retention. The parameters of the kinetic model estimated under isothermal conditions provided an adequate prediction of texture changes under non-isothermal conditions. The methodology developed in this work can be further applied to model the textural changes of vegetables during other thermal processes, such as drying, blanching, and frying.
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| 3. |
- Gomez, Federico, et al.
(författare)
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Cold acclimation of carrots during storage mechanical properties and antifreezing protein.
- 2003
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Ingår i: Acta horticulturae : technical communications of ISHS. - 0567-7572. ; 599, s. 699-703
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Konferensbidrag (refereegranskat)abstract
- Changes in the composition of carrot cell wall proteins were investigated, associating metabolic changes during long-term storage with changes in mechanical properties. Harvested carrots accumulate an antifreezing protein in their cell walls reaching a maximum level after 12 weeks of storage at 0°C, followed by a gradual decrease. During the same period of time, there is a decrease in the slicing force during the first 7 weeks of storage followed by an increase until the 12th week. The appearance and accumulation of the antifreezing protein suggest that structural changes leading to changes in mechanical properties during the first 12 weeks of storage might be associated with a cold acclimation process.
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| 4. |
- Jacobsson, A., et al.
(författare)
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Influence of packaging material and storage temperature on texture, colour, and weight of broccoli.
- 2003
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Ingår i: ISHS Acta Horticulturae. - 0567-7572. ; 600, s. 323-323
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Konferensbidrag (refereegranskat)abstract
- Sophisticated packaging solutions can be used in order to preserve vegetables during storage and transport. Polymeric films with selective barriers matching the respiration of the produce, thereby creating an ideal atmosphere inside the package, are available on the market. Fresh broccoli (Brassica oleracea L. var. italica ‘Monterey’) heads were packed in 4 different commercially available polymeric films, and stored at 4 and 10°C respectively. During storage the weight, colour, chlorophyll content and texture were monitored. The investigated polymer materials were oriented polypropylene (OPP), polyvinyl chloride (PVC) and two types of polyethylene (PE) packagings. The choice of packaging material had an impact on the measured quality parameters of broccoli. Storage in OPP resulted in the longest storage life. Broccoli stored in PVC film deteriorated faster than broccoli packaged in the other materials. It was also observed that the influence of the type of packaging material was more important at the higher temperature. The implications of this work for the packaging and storage of fresh broccoli will be discussed.
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| 5. |
- Jacobsson, A., et al.
(författare)
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The effect of packaging material on the sensory properties of broccoli.
- 2003
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Ingår i: ISHS Acta Horticulturae. - 0567-7572. ; 599, s. 323-323
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Konferensbidrag (refereegranskat)abstract
- Three different commercially available polymeric films were studied to determine their effect on the sensory properties of fresh broccoli (Brassica oleracea L. var. Italica cv. ‘Marathon’). The polymer materials investigated were oriented polypropylene (OPP), polyvinyl chloride (PVC) and one low density polyethylene (LDPE) which contained an ethylene absorber. The fresh broccoli was packaged and stored for one week at 10°C or 3 days at 4°C followed by 4 days at 10°C. The oxygen and carbon dioxide concentrations inside the packages were monitored during storage. After storage the broccoli was evaluated according to sensory analyses, i.e. triangle test and quantitative descriptive analysis, by an analytical panel. The panel judged the broccoli according to smell, taste, texture and appearance. The triangle test showed significant differences between the smell of the broccoli samples, stored in the different packaging materials, when cooked. However, no differences between the raw broccoli, stored in the different packaging materials could be detected. The quantitative descriptive analysis showed that the following attributes; fresh smell and taste, chewing resistance, and crispness, differed significantly between the packaged broccoli when cooked. The appearance was shown to be the sensory property of broccoli most affected by the storage conditions, i.e. packaging material used and storage temperature. The results indicated the importance of the packaging material for maintaining the broccoli quality. However, one packaging material that was able to maintain all the studied sensory properties could not be identified.
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| 6. |
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| 7. |
- Mattsson, Berit, et al.
(författare)
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Environmental Life Cycle Assessment (LCA) of organic potatoes
- 2003
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Ingår i: Acta Horticulturae. - 0567-7572. ; 619, s. 427-435
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Tidskriftsartikel (refereegranskat)abstract
- An LCA of organic potatoes cultivated in southern Sweden was carried out to gain more knowledge about the environmental impact and resource use along the food chain. Life Cycle Assessment (LCA) is a method for analysis and assessment of the potential environmental impact caused by products (ISO 14040). Included in the study were the production of inputs to agriculture, agricultural production, sorting and packaging, distribution and the household phase. The use of energy, water and other resources were also included as well as basic environmental impact categories such as global warming, acidification, eutrophication, toxicity, ozone depletion and photo-oxidant formation. A major finding was that the agricultural production accounted for almost all the emissions contributing to eutrophication and acidification. Other findings were that agricultural production, production of packaging materials and the household phase were the main contributors to global warming, while the energy use was rather evenly distributed among the life cycle stages. The primary improvement options identified in the study were to reduce nitrogen emissions contributing to acidification and eutrophication and to reduce potato losses due to poor quality. The organic potato yields are generally very low, typically about 60% of the conventional levels. Increased yields would be beneficial from an environmental point of view.
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| 8. |
- Richert-Stintzing, A., et al.
(författare)
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Application of broiler chicken manure to lettuce and cabbage crops. : Effect on yield, plant nutrient utilisation and mineral nitrogen in soil
- 2002
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Ingår i: Acta Horticulturae. - 0567-7572. ; 571, s. 119-126
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Tidskriftsartikel (refereegranskat)abstract
- The use of broiler chicken manure is increasing in Sweden due to its reputation as a quick-acting nitrogen fertiliser. However, data concerning the effects on crops and the environment are limited. In 1998, a field trial was carried out at Ultuna with the aim of investigating the effects of spreading two different quantities of pelleted and stored broiler manure to iceberg lettuce and white cabbage. The parameters studied were yield, plant nutrient utilisation and amount of soil mineral nitrogen. Results from the field trial show that the pelleted broiler manure gave a better effect on yield than stored broiler manure. Nutrient balances showed that it is difficult to attain a good balance between application and uptake of nutrients when using broiler manure, especially pelleted. Soil samples indicate that the amount of mineral nitrogen in the soil after harvest did not differ significantly between the two broiler manures at the two levels of application. The results from this first year of field trials need to be confirmed with further trials.
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| 9. |
- Tjärnemo, Heléne, et al.
(författare)
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Consumers choice of organic versus conventional fruit and vegetables - The role of the grocery store
- 2004
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Ingår i: Proceedings of the XV International Symposium on Horticultural Economics and Management. - 0567-7572. - 9789066050563 ; :655, s. 115-120
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Konferensbidrag (refereegranskat)abstract
- This paper presents findings from two explorative studies. One is a consumer study based on interviews with consumers in real store settings and one is a study based on interviews with fruit and vegetable managers of stores affiliated with a major food retail chain in Sweden. The aim of both studies was to explore the role of the grocery store for the consumers' choice of organic versus conventional fruit and vegetables. The empirical data was analysed by using Perspective Text Analysis (PTA), an approach that aims at revealing the central message of a verbal or written text. The analyses showed that the main approach towards how to choose fruit and vegetables differed between consumers who bought and consumers who did not buy organic fruit and vegetables. While the first group was health-oriented, the second group was more meal-oriented. Organic fruit and vegetables were perceived as coherent with the first group's health-oriented buying approach, but as incoherent with the basic quality standards of the second group. The meal-oriented consumers perceived the grocery store as a source of inspiration for their meal planning, and for that reason the store could play a significant role by promoting organic alternatives. However, the study of fruit and vegetable managers indicated that grocery stores could not be expected to promote organic fruit and vegetables, since the fruit and vegetable managers considered organically grown to be of marginal interest from both a store and a consumer perspective. The two studies highlight one of the main difficulties that tie ahead of continues market growth of organic fruit and vegetables, i.e. how to reach the less devoted majority of consumers if the food retailers perceive organically grown as uninterested products.
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