Effects of prefreezing treatments on the structure of strawberries and jams: Dissertation

Marjaana Suutarinen

Research output: ThesisDissertation

1 Citation (Scopus)

Abstract

Different chemical components and their locations in strawberry (Fragaria x ananassa) achenes, vascular bundles and cortical cell walls were studied by means of bright-field microscopy using different staining systems and by Fourier transform infrared (FT-IR) microscopy. The structural changes in pretreated strawberry tissues during freezing and thawing were studied by means of physical and chemical analyses as well as by bright-field and FT-IR microscopy, and by confocal laser scanning (CLS) microscopy. In addition, traditional jams made from pretreated frozen strawberries were investigated by means of physical and chemical analyses and by sensory evaluation. Basic microstructural studies showed that all the cell walls were complex and consisted of several components. Lignin was an important component of achenes and vascular tissues, whereas the cortical cell walls contained mainly cellulose, pectin and some protein. Cellulose and pectin were also detectable in the intercellular spaces of cortex, in the vascular tissue and pith. Protein was deposited inside the cortical cells, as well as in the vascular tissue and pith. The microscopical methods used gave comparable results. According to microscopical studies both the pretreatments with calcium chloride (CaCl2) and crystallised sucrose as well with CaCl2 and pectin methyesterase (PME) in a vacuum affected the microstructure of strawberry tissues. These pretreatments especially affected pectin, protein, lignin and structural carbohydrates in the vascular tissue and cortex compared to the untreated reference samples. The use of a vacuum appeared to make the pretreatment solutions absorb more efficiently to the cortex and pith, thus improving the stabilisation particularly of pectin and structural carbohydrates. Firmness of thawed and particularly of jam strawberries pretreated with CaCl2 and PME in a vacuum was higher than that of other pretreated or untreated berries. In all the prefreezing treatments studied, dipping of strawberries into a CaCl2 solution with PME in a vacuum resulted in a significantly different sensory profile than was found in the other jams. The sensory attributes wholeness of the berries (p<0.001), firmness, clarity and evenness of the jam medium (p<0.001), softness of the berries (p<0.001) and faultlessness of odour and flavour (p<0.001) in particular were statistically significantly different among the strawberry jams. Sensory quality was perceived to decrease during 4 months of storage, even though the shapes of the sensory profiles of the studied jams did not change significantly from those evaluated after 2 weeks storage. For achieving high quality jams the pretreatment time should be short (about 5-15 min), the temperature low (below 20 °C), the vacuum level high (pressure less than 10 kPa), the CaCl2 concentration moderate (about 1%) and the dosage of PME comparatively low (about 50-100 µkat/kg strawberries).
Original languageEnglish
QualificationDoctor Degree
Awarding Institution
  • Aalto University
Supervisors/Advisors
  • Autio, Karin, Supervisor, External person
Award date19 Apr 2002
Place of PublicationEspoo
Publisher
Print ISBNs951-38-5979-9
Electronic ISBNs951-38-5980-0
Publication statusPublished - 2002
MoE publication typeG5 Doctoral dissertation (article)

Fingerprint

jams
pectins
strawberries
calcium chloride
vascular tissues
pith
pretreatment
small fruits
microscopy
cortex
cell walls
firmness
lignin
cellulose
carbohydrates
fruits
proteins
intercellular spaces
Fragaria ananassa
confocal laser scanning microscopy

Keywords

  • Calcium chloride
  • pectin methylesterase
  • sucrose
  • vacuum
  • strawberry
  • structure
  • prefreezing
  • jam

Cite this

Suutarinen, M. (2002). Effects of prefreezing treatments on the structure of strawberries and jams: Dissertation. Espoo: VTT Technical Research Centre of Finland.
Suutarinen, Marjaana. / Effects of prefreezing treatments on the structure of strawberries and jams : Dissertation. Espoo : VTT Technical Research Centre of Finland, 2002. 101 p.
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title = "Effects of prefreezing treatments on the structure of strawberries and jams: Dissertation",
abstract = "Different chemical components and their locations in strawberry (Fragaria x ananassa) achenes, vascular bundles and cortical cell walls were studied by means of bright-field microscopy using different staining systems and by Fourier transform infrared (FT-IR) microscopy. The structural changes in pretreated strawberry tissues during freezing and thawing were studied by means of physical and chemical analyses as well as by bright-field and FT-IR microscopy, and by confocal laser scanning (CLS) microscopy. In addition, traditional jams made from pretreated frozen strawberries were investigated by means of physical and chemical analyses and by sensory evaluation. Basic microstructural studies showed that all the cell walls were complex and consisted of several components. Lignin was an important component of achenes and vascular tissues, whereas the cortical cell walls contained mainly cellulose, pectin and some protein. Cellulose and pectin were also detectable in the intercellular spaces of cortex, in the vascular tissue and pith. Protein was deposited inside the cortical cells, as well as in the vascular tissue and pith. The microscopical methods used gave comparable results. According to microscopical studies both the pretreatments with calcium chloride (CaCl2) and crystallised sucrose as well with CaCl2 and pectin methyesterase (PME) in a vacuum affected the microstructure of strawberry tissues. These pretreatments especially affected pectin, protein, lignin and structural carbohydrates in the vascular tissue and cortex compared to the untreated reference samples. The use of a vacuum appeared to make the pretreatment solutions absorb more efficiently to the cortex and pith, thus improving the stabilisation particularly of pectin and structural carbohydrates. Firmness of thawed and particularly of jam strawberries pretreated with CaCl2 and PME in a vacuum was higher than that of other pretreated or untreated berries. In all the prefreezing treatments studied, dipping of strawberries into a CaCl2 solution with PME in a vacuum resulted in a significantly different sensory profile than was found in the other jams. The sensory attributes wholeness of the berries (p<0.001), firmness, clarity and evenness of the jam medium (p<0.001), softness of the berries (p<0.001) and faultlessness of odour and flavour (p<0.001) in particular were statistically significantly different among the strawberry jams. Sensory quality was perceived to decrease during 4 months of storage, even though the shapes of the sensory profiles of the studied jams did not change significantly from those evaluated after 2 weeks storage. For achieving high quality jams the pretreatment time should be short (about 5-15 min), the temperature low (below 20 °C), the vacuum level high (pressure less than 10 kPa), the CaCl2 concentration moderate (about 1{\%}) and the dosage of PME comparatively low (about 50-100 µkat/kg strawberries).",
keywords = "Calcium chloride, pectin methylesterase, sucrose, vacuum, strawberry, structure, prefreezing, jam",
author = "Marjaana Suutarinen",
year = "2002",
language = "English",
isbn = "951-38-5979-9",
series = "VTT Publications",
publisher = "VTT Technical Research Centre of Finland",
number = "462",
address = "Finland",
school = "Aalto University",

}

Suutarinen, M 2002, 'Effects of prefreezing treatments on the structure of strawberries and jams: Dissertation', Doctor Degree, Aalto University, Espoo.

Effects of prefreezing treatments on the structure of strawberries and jams : Dissertation. / Suutarinen, Marjaana.

Espoo : VTT Technical Research Centre of Finland, 2002. 101 p.

Research output: ThesisDissertation

TY - THES

T1 - Effects of prefreezing treatments on the structure of strawberries and jams

T2 - Dissertation

AU - Suutarinen, Marjaana

PY - 2002

Y1 - 2002

N2 - Different chemical components and their locations in strawberry (Fragaria x ananassa) achenes, vascular bundles and cortical cell walls were studied by means of bright-field microscopy using different staining systems and by Fourier transform infrared (FT-IR) microscopy. The structural changes in pretreated strawberry tissues during freezing and thawing were studied by means of physical and chemical analyses as well as by bright-field and FT-IR microscopy, and by confocal laser scanning (CLS) microscopy. In addition, traditional jams made from pretreated frozen strawberries were investigated by means of physical and chemical analyses and by sensory evaluation. Basic microstructural studies showed that all the cell walls were complex and consisted of several components. Lignin was an important component of achenes and vascular tissues, whereas the cortical cell walls contained mainly cellulose, pectin and some protein. Cellulose and pectin were also detectable in the intercellular spaces of cortex, in the vascular tissue and pith. Protein was deposited inside the cortical cells, as well as in the vascular tissue and pith. The microscopical methods used gave comparable results. According to microscopical studies both the pretreatments with calcium chloride (CaCl2) and crystallised sucrose as well with CaCl2 and pectin methyesterase (PME) in a vacuum affected the microstructure of strawberry tissues. These pretreatments especially affected pectin, protein, lignin and structural carbohydrates in the vascular tissue and cortex compared to the untreated reference samples. The use of a vacuum appeared to make the pretreatment solutions absorb more efficiently to the cortex and pith, thus improving the stabilisation particularly of pectin and structural carbohydrates. Firmness of thawed and particularly of jam strawberries pretreated with CaCl2 and PME in a vacuum was higher than that of other pretreated or untreated berries. In all the prefreezing treatments studied, dipping of strawberries into a CaCl2 solution with PME in a vacuum resulted in a significantly different sensory profile than was found in the other jams. The sensory attributes wholeness of the berries (p<0.001), firmness, clarity and evenness of the jam medium (p<0.001), softness of the berries (p<0.001) and faultlessness of odour and flavour (p<0.001) in particular were statistically significantly different among the strawberry jams. Sensory quality was perceived to decrease during 4 months of storage, even though the shapes of the sensory profiles of the studied jams did not change significantly from those evaluated after 2 weeks storage. For achieving high quality jams the pretreatment time should be short (about 5-15 min), the temperature low (below 20 °C), the vacuum level high (pressure less than 10 kPa), the CaCl2 concentration moderate (about 1%) and the dosage of PME comparatively low (about 50-100 µkat/kg strawberries).

AB - Different chemical components and their locations in strawberry (Fragaria x ananassa) achenes, vascular bundles and cortical cell walls were studied by means of bright-field microscopy using different staining systems and by Fourier transform infrared (FT-IR) microscopy. The structural changes in pretreated strawberry tissues during freezing and thawing were studied by means of physical and chemical analyses as well as by bright-field and FT-IR microscopy, and by confocal laser scanning (CLS) microscopy. In addition, traditional jams made from pretreated frozen strawberries were investigated by means of physical and chemical analyses and by sensory evaluation. Basic microstructural studies showed that all the cell walls were complex and consisted of several components. Lignin was an important component of achenes and vascular tissues, whereas the cortical cell walls contained mainly cellulose, pectin and some protein. Cellulose and pectin were also detectable in the intercellular spaces of cortex, in the vascular tissue and pith. Protein was deposited inside the cortical cells, as well as in the vascular tissue and pith. The microscopical methods used gave comparable results. According to microscopical studies both the pretreatments with calcium chloride (CaCl2) and crystallised sucrose as well with CaCl2 and pectin methyesterase (PME) in a vacuum affected the microstructure of strawberry tissues. These pretreatments especially affected pectin, protein, lignin and structural carbohydrates in the vascular tissue and cortex compared to the untreated reference samples. The use of a vacuum appeared to make the pretreatment solutions absorb more efficiently to the cortex and pith, thus improving the stabilisation particularly of pectin and structural carbohydrates. Firmness of thawed and particularly of jam strawberries pretreated with CaCl2 and PME in a vacuum was higher than that of other pretreated or untreated berries. In all the prefreezing treatments studied, dipping of strawberries into a CaCl2 solution with PME in a vacuum resulted in a significantly different sensory profile than was found in the other jams. The sensory attributes wholeness of the berries (p<0.001), firmness, clarity and evenness of the jam medium (p<0.001), softness of the berries (p<0.001) and faultlessness of odour and flavour (p<0.001) in particular were statistically significantly different among the strawberry jams. Sensory quality was perceived to decrease during 4 months of storage, even though the shapes of the sensory profiles of the studied jams did not change significantly from those evaluated after 2 weeks storage. For achieving high quality jams the pretreatment time should be short (about 5-15 min), the temperature low (below 20 °C), the vacuum level high (pressure less than 10 kPa), the CaCl2 concentration moderate (about 1%) and the dosage of PME comparatively low (about 50-100 µkat/kg strawberries).

KW - Calcium chloride

KW - pectin methylesterase

KW - sucrose

KW - vacuum

KW - strawberry

KW - structure

KW - prefreezing

KW - jam

M3 - Dissertation

SN - 951-38-5979-9

T3 - VTT Publications

PB - VTT Technical Research Centre of Finland

CY - Espoo

ER -

Suutarinen M. Effects of prefreezing treatments on the structure of strawberries and jams: Dissertation. Espoo: VTT Technical Research Centre of Finland, 2002. 101 p.