2.4. Texture analysis
Fruit firmness was measured with a penetrometer using
a 9.6 mm2 surface needle, and three punctures from opposite
sites per fruit. Firmness of intact (external firmness)
and peeled fruits (internal firmness) were recorded in at
least 100 fruits per line.
After 1 week of storage at 4 C, jams were equilibrated
at 23 C for 2 h, and then, placed over a 2 mm2-holed plastic
net to separate medium and fruits. Both jam fractions
were weighed and the data recorded as the percentage of
initial jam weight.
Firmness of berries and medium were measured separately
by back extrusion tests using a Texture Analyser
(Taxt-plus, Stable Micro System, UK). To this purpose, a
cylindrical container of 95 mm height and 52 mm internal
diameter, as well as a loose-fitting, flat-cylindrical plunger
of 45 mm diameter were used. Container was filled with
berries, 90 g, or medium, 50 mm height. Compression test
started when the plunger got in contact with product surface,
and finished when a 95% strain of the sample was
reached. Plunger speed during compression was 1.5 mm/s
for berries and medium. After compression, the plunger
moved upward and the tension forces were recorded. Plunger
speed during tension test was 15 mm/s in the case of
fruits and 40 mm/s for medium.
Several parameters were calculated in the back extrusion
tests using the Texture Analyser software. In the case of
jam fruits, the gradient of initial compression, compression
force, mean peak drop off, area of deformation curve and
area of tension curve, reported as adhesiveness, were
recorded as the results. Gradient was calculated taking
the first portion of the compression curve, from the initial
2.4. Texture analysisFruit firmness was measured with a penetrometer usinga 9.6 mm2 surface needle, and three punctures from oppositesites per fruit. Firmness of intact (external firmness)and peeled fruits (internal firmness) were recorded in atleast 100 fruits per line.After 1 week of storage at 4 C, jams were equilibratedat 23 C for 2 h, and then, placed over a 2 mm2-holed plasticnet to separate medium and fruits. Both jam fractionswere weighed and the data recorded as the percentage ofinitial jam weight.Firmness of berries and medium were measured separatelyby back extrusion tests using a Texture Analyser(Taxt-plus, Stable Micro System, UK). To this purpose, acylindrical container of 95 mm height and 52 mm internaldiameter, as well as a loose-fitting, flat-cylindrical plungerof 45 mm diameter were used. Container was filled withberries, 90 g, or medium, 50 mm height. Compression teststarted when the plunger got in contact with product surface,and finished when a 95% strain of the sample wasreached. Plunger speed during compression was 1.5 mm/sfor berries and medium. After compression, the plungermoved upward and the tension forces were recorded. Plungerspeed during tension test was 15 mm/s in the case offruits and 40 mm/s for medium.Several parameters were calculated in the back extrusiontests using the Texture Analyser software. In the case ofjam fruits, the gradient of initial compression, compressionforce, mean peak drop off, area of deformation curve andarea of tension curve, reported as adhesiveness, wererecorded as the results. Gradient was calculated takingthe first portion of the compression curve, from the initial
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