Abstract
Abstract The effects of water, sorbitol and a sucrose fatty acid ester (SE) on the water sorption behaviour and thermal and mechanical properties of pullulan‐based edible films as well as the physiological responses of fruit coated with pullulan have been studied. Incorporation of sorbitol or SE in pullulan films resulted in lower equilibrium moisture contents at low to intermediate water activities ( a w ), but much higher moisture contents at a w > 0.75; estimates of monolayer values (within 4.1–5.9 gH 2 O kg −1 solids) were given by application of the Brunauer–Emmett–Teller (BET) and Guggenheim–Anderson–DeBoer (GAB) models. A single glass–rubber transition ( T g ), attributed to the polysaccharide component, was detected by calorimetry and dynamic mechanical thermal analysis (DMTA) at a sorbitol level of 15–30% DM. With both tests the strong plasticising action of water and polyol was evident in the thermal curves, and the T g vs moisture content data were successfully fitted to the Gordon–Taylor empirical model. Multifrequency DMTA measurements provided estimates for the apparent activation energy of the glass transition in the range of ˜ 300–488 kJ mol −1 . With large‐deformation mechanical testing, large decreases in Young's moduli (tensile and three‐point bend tests) were observed as a result of water‐ and/or polyol‐mediated glass‐to‐rubber transition of the polymeric films. In the moisture content range of 2–8%, increases in flexural modulus ( E ) and maximum stress (σ max ) with small increases in moisture content were found for films made of pullulan or pullulan mixed with 15% DM sorbitol; a strong softening effect was observed when the water content exceeded this range. Addition of sorbitol increased the water vapour transmission rate of the films, whereas addition of SE had the opposite effect. Application of a pullulan/sorbitol/SE coating on strawberries resulted in large changes in internal fruit atmosphere composition which were beneficial for extending the shelf‐life of this fruit; the coated fruit showed much higher levels of CO 2 , a large reduction in internal O 2 , better firmness and colour retention and a reduced rate of weight loss. In contrast, similar studies on whole kiwifruits showed increased levels of internal ethylene, which caused acceleration of fruit ripening during storage. © 2001 Society of Chemical Industry
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Claims 10
Claim · model-written summary
Coated strawberries showed much higher internal CO 2 levels.
- Taxon
- strawberries
_single2.jpg?width=60)
Fragaria ×ananassae0 - Treatment
- pullulan/sorbitol/SE coatinge0
- Outcome
- levels of CO 2e1
- Direction
- much highere1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
_single2.jpg?width=500)
Verbatim
e0“Application of a pullulan/sorbitol/SE coating on strawberries”
e1“the coated fruit showed much higher levels of CO 2”
Claim · model-written summary
Coated strawberries showed a large reduction in internal O 2.
- Taxon
- strawberriesFragaria ×ananassae0
- Treatment
- pullulan/sorbitol/SE coatinge0
- Outcome
- internal O 2e2
- Direction
- large reductione2
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Application of a pullulan/sorbitol/SE coating on strawberries”
e2“a large reduction in internal O 2”
Claim · model-written summary
Coated strawberries had better firmness and colour retention.
- Taxon
- strawberriesFragaria ×ananassae0
- Treatment
- pullulan/sorbitol/SE coatinge0
- Outcome
- firmness and colour retentione3
- Direction
- bettere3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Application of a pullulan/sorbitol/SE coating on strawberries”
e3“better firmness and colour retention”
Claim · model-written summary
Coated strawberries had a reduced rate of weight loss.
- Taxon
- strawberriesFragaria ×ananassae0
- Treatment
- pullulan/sorbitol/SE coatinge0
- Outcome
- rate of weight losse4
- Direction
- reducede4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Application of a pullulan/sorbitol/SE coating on strawberries”
e4“a reduced rate of weight loss”
Claim · model-written summary
Whole kiwifruits in similar studies showed increased internal ethylene levels.
Verbatim
e5“similar studies on whole kiwifruits showed increased levels of internal ethylene”
Claim · model-written summary
The increased internal ethylene caused accelerated ripening of kiwifruit during storage (author interpretation).
- Taxon
- kiwifruits
Actinidia deliciosae5 - Compound
- ethylenee5
- Outcome
- acceleration of fruit ripeninge6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e5“similar studies on whole kiwifruits showed increased levels of internal ethylene”
e6“which caused acceleration of fruit ripening during storage”
Claim · model-written summary
Adding sorbitol increased the water vapour transmission rate of the films.
Not reportedTaxonComparator
Verbatim
e1“Addition of sorbitol increased the water vapour transmission rate of the films”
Claim · model-written summary
Adding SE decreased the water vapour transmission rate of the films.
Not reportedTaxonComparator
Verbatim
e1“Addition of sorbitol increased the water vapour transmission rate of the films”
e2“whereas addition of SE had the opposite effect”
Claim · model-written summary
Sorbitol or SE in pullulan films lowered equilibrium moisture contents at low to intermediate water activities.
- Treatment
- Incorporation of sorbitol or SE in pullulan filmse1
- Outcome
- equilibrium moisture contentse1
- Direction
- lowere1
Not reportedTaxonComparator
Verbatim
e1“Incorporation of sorbitol or SE in pullulan films resulted in lower equilibrium moisture contents at low to intermediate water activities”
Claim · model-written summary
Large decreases in Young's moduli were observed with water- and polyol-mediated glass-to-rubber transition of the films.
Not reportedTaxon
Verbatim
e1“large decreases in Young's moduli”
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