共查询到20条相似文献,搜索用时 31 毫秒
1.
M. José Esteve A. Frígola L. Martorell Carmen Rodrigo 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1999,208(2):144-147
Thermal degradation of green asparagus ascorbic acid in high-temperature short-time conditions was studied by heating in
a five-channel computer-controlled thermoresistometer. Ascorbic acid was heated to between 110 °C and 140 °C and the degradation
kinetics were analyzed assuming that two different inactivation mechanisms were occurring, one aerobic and the other anaerobic.
The two reactions followed first-order kinetics, with E
a=12.3(2.0) kcal/mol and k
125 °C=47.0(3.0)×10–3 s–1 for the aerobic oxidation, and E
a=6.1(1.4) kcal/mol and k
125 °C=4.1(0.2)×10–3 s–1 for the anaerobic degradation.
Received: 30 January 1998 / Revised version: 11 June 1998 相似文献
2.
Emma S. Sánchez Susana Simal Antoni Femenia José Benedito C. Rosselló 《European Food Research and Technology》1999,209(3-4):215-219
The effect of ultrasound on mass transfer during cheese brining has been investigated. The rate of water removal and NaCl
gain increased when ultrasound was applied in comparison with brining performed under static or dynamic conditions, suggesting
that ultrasound improves both external and internal mass transfer. A simple diffusional model was developed to simulate mass
transport during acoustic brining. Model parameters were estimated using experimental data from acoustic brining experiments
carried out on cheese cylinders of 1.7×10–2 m radius and 3×10–2 m height at different temperatures (5, 15 and 20 °C). Effective water (D
W) and NaCl (D
S) diffusivities estimated using the proposed model ranged from 5.0×10–10 m2/s and 8.0×10–10 m2/s at 5 °C to 1.3×10–9 m2/s and 1.2×10–9 m2/s at 20 °C. Both D
W and D
S varied with temperature according to the Arrhenius equation. Through the proposed model, water losses and NaCl gains of the
experiments used in the parameter identification were accurately simulated (average %var=98.2%) and also of two additional
acoustic experiments carried out under different conditions of temperature (10 °C) and sample size and geometry [parallelepiped
of (6×2.5×1.25)×10–2 m] to those used in the parameter identification (average %var=98.4%).
Received: 22 September 1998 / Revised version: 20 November 1998 相似文献
3.
G. Began B. Manohar K. Udaya Sankar A.G. Appu Rao 《European Food Research and Technology》2000,210(3):209-212
The solubility of soy lecithin lipids in supercritical CO2 was measured at pressures of 120, 200 and 280 bar and at temperatures of 40, 50 and 60 °C. The effects of temperature and
pressure on the solubility of total lipids were studied by response surface methodology. The response surface equation to
predict the solubility of total lipids in the above range of pressure and temperature is: Y=–3.237+0.0431* P–7.3×10–5
P
2–0.00011 P*T where Y is the total lipid solubility in g/kg CO2, P is the pressure in bar and T is the temperature in °C. The total lipids solubility increased with pressure at constant temperature, but decreased with
increasing temperature. The total lipids consisted of a very small phospholipid content compared to neutral lipids and glycolipids
at all the pressures and temperatures studied. Optimum search indicated a maximum solubility of total lipids of 1.829 g/kg
CO2 at 263 bar and 40 °C.
Received: 1 April 1999 相似文献
4.
N. Turker Yalçin Coşkuner H. Í. Ekiz Salih Aksay Erşan Karababa 《European Food Research and Technology》2001,212(2):213-216
Cactus pear (Opuntia ficus-indica) juice with a total soluble solids content of 15.94 °Brix was fermented using the wine yeast Saccharomyces cerevisiae. A 94.54% conversion of fermentable sugar was achieved with an ethanol production of 55.3 ml/l. The pigment degradation was
found to be 17% at the end of the time allowed for fermentation. However, the fermentation had actually ceased due to depletion
of fermentable sugars after 12 h, a point at which only 9.4% pigment degradation was observed and there was no further total
soluble solids degradation. The thermal stability of the yellow-orange pigment of the fermented juice was determined as a
function of temperature at pH 5.0. The kinetic experiments were carried out at three different temperatures, 50, 70 and 90 °C.
For a pseudo-first order thermal degradation rate the reaction rate constants were determined to be 0.0066, 0.0206 and 0.1244 min–1 for temperatures of 50, 75 and 90 °C, respectively. The activation energy was calculated as 15.71 kcal mole–1. The fermentation process did not affect the thermostability of the pigment extract.
Received: 10 January 2000 / Revised version: 31 March 2000 相似文献
5.
Response surface methodology was used to compare the effect of temperature and time of the first step of blanching on compression,
shear, tension and stress-relaxation parameters of frozen-thawed potato tissues. A central, composite rotatable design was
used to study the effects of variation in levels of temperature (52.93–67.07 °C) and time (15.86–44.14 min) on rheological
parameters. Blanching temperature was the most important factor affecting the mechanical properties tested. The models fitted
for the apparent modulus of elasticity in compression, maximum tension force, and relaxed force in the first cycle (F
r1); all had R
2>0.85 (P≤0.01) and were used for doing predictions. Optimum conditions were with in the ranges of temperature (60–65 °C) and time
(25–35 min) used for each factor. In the experimental verification of the models at 65 °C during 30 min, the lowest percentage
residual between experimental and predicted values was obtained for F
r1 (0.644), which was therefore the most appropiate parameter for detecting the firming effect that the pectinesterase activity
produced on frozen potato tissues as a consequence of stepwise blanching under these conditions.
Received: 3 February 1999 / Revised version: 12 April 1999 相似文献
6.
Marisol Castañer María I. Gil M. Victoria Ruíz F. Artés 《European Food Research and Technology》1999,209(1):52-56
This study was conducted to determine the effects of cultivar, tissue susceptibility and storage temperature on the keeping
quality of minimally processed Baby and Romaine lettuces. Midrib and photosynthetic tissues were lightly processed and stored
for up to 7 days at 5 °C and 13 °C. Changes in L
* and a
* values and absorbance at 430 nm were compared. The relationship between polyphenols, phenylalanine ammonia lyase (PAL) and
polyphenol oxidase (PPO) activities and browning was examined. Measurements of L
* and a
* values on midribs showed that browning discoloration was the same for Baby as for Romaine lettuces and there was no relationship
for temperature. In addition, L
* and a
* values in photosynthetic tissue indicated a decrease in green pigmentation during storage, especially at 13 °C. For both
kinds of tissue at the end of cold storage an increase in soluble brown polymers was detected. In midribs, total phenolics
increased significantly throughout the storage period because of the tissue-wounding response. The photosynthetic tissue had
a higher phenolic content than the midrib one. For both kinds of tissue an increase in PPO activity occurred throughout cold
storage. On the other hand, PAL activity in midrib tissue only increased initially, followed by a slow decline to reach normal
levels. Browning potential estimated by L
* values correlated significantly (P>95%) with PPO activity and with absorbance at 430 nm for Romaine lettuce. Based on colour and browning potential no differences
between Romaine and Baby lettuce cultivars were observed. However, photosynthetic tissue was the most suitable tissue for
the preparation of minimally processed salad mixes because of its high phenolic content.
Received: 28 September 1998 相似文献
7.
Ankit Patras Nigel P. Brunton B. K. Tiwari Francis Butler 《Food and Bioprocess Technology》2011,4(7):1245-1252
The effect of storage time and temperature on degradation of bioactive compounds such as ascorbic acid, anthocyanins, total
phenols, colour and total antioxidant capacity of strawberry jam were investigated. The results indicated that lightness (L) value decreased significantly (p < 0.05) over 28 days of storage at 4 and 15 °C, with lower values measured at higher temperatures. Anthocyanins, ascorbic
acid and colour degradation followed first-order kinetics where the rate constant increased with an increase in the temperature.
The reaction rate constant (k) increased from 0.95 × 10−2 day−1 to 1.71 × 10−2 day−1 at 4 and 15 °C for anthocyanins. Similarly, k increased from 2.08 × 10−2 day−1 to 4.54 × 10−2 day−1 at 4 and 15 °C for ascorbic acid. In general, total antioxidant activity for strawberry jam samples stored for 28 days at
4 and 15 °C exhibited lower values as compared to control (day 0). The results showed greater stability of nutritional parameters
at 4 °C compared to 15 °C. 相似文献
8.
Use of β-hydroxyacyl-CoA-dehydrogenase (HADH) activity to differentiate frozen from unfrozen fish and shellfish 总被引:1,自引:0,他引:1
Manuela Fernández Sergio Mano Gonzalo D. García de Fernando Juan A. Ordóñez L. Hoz 《European Food Research and Technology》1999,209(3-4):205-208
Further work on an enzymic method to differentiate frozen from unfrozen fish and shellfish is reported. The method is based
on the release of the β-hydroxyacyl-CoA-dehydrogenase (HADH) from mitochondria during freezing. Enzymic activity was evaluated
in fresh and frozen thawed samples from sole (Solea solea), sea bream (Pagellus centrodontus), hake (Merluccius merluccius), gilt headed bream (Sparus aurata), sea bass (Dicentrarchus labrax), salmon (Salmo salar), prawn (Penaeus japonicus) and Norwegian lobster (Nephrops norvegicus). Changes in the HADH activity of fresh and frozen thawed samples were compared after freezing at –196 °C for 15 min. Two
values were obtained: U (by dividing: HADH activity of samples frozen at –196 °C, then thawed/HADH activity of unfrozen samples) and F (by dividing: HADH activity of samples frozen at –18 °C, thawed, then frozen at –196 °C /HADH activity of samples frozen
at –18 °C, then thawed). Statistical analysis showed significant differences (P≤0.05) between both quotients for gilt headed bream, salmon, sea bream, sole and prawn, and an arbitrary limit was set at
2 to differentiate frozen thawed from unfrozen samples. The application of this limit made it possible to discriminate the
unfrozen from the frozen thawed state of around 90% of the total samples analysed. Best results were obtained for prawn (100%
of samples differentiated). In the present paper, a laboratory routine is proposed based on the comparison of the HADH activity
of a sample analysed straight away and that of a sample frozen at –196 °C and then thawed. The reported method is simple
and fast. The entire laboratory procedure can be performed in 45 min.
Received: 20 July 1998 / Revised version: 2 November 1998 相似文献
9.
Wojciech Ciesielski P. Tomasik 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1998,207(4):292-298
Nine starch varieties were blended and kneaded with d-fructose, d-glucose, sucrose, egg albumin and/or ethyl stearate to form semiartificial complexes. They were then thermolyzed and the
numbers of unpaired spins in the solid residues were determined. Individual starch varieties began to generate unpaired spin
states within 2 h of heating at 285 °C but some starch blends, particularly those of four-component starch (10 : 1 : 1 : 1)
mixtures, generated free radicals within 2 h of heating at 160 °C. However, the free radical counts were minimized by the
mutual complexation of the blend components and, to a certain extent, by the free radical scavenging in the blends.
Received: 21 October 1997 / Revised version: 15 April 1998 相似文献
10.
Radomír Pecháček Jan Velíšek Jiří Davídek 《European Food Research and Technology》2000,210(3):196-201
Sinigrin (allylglucosinolate) was stored at 20 °C, 40 °C, and 60 °C in solutions containing 10% ammonia in 95% methanol
(CH3OH/NH3/H2O). The individual samples were analyzed for their contents of sinigrin, its decomposition product allyl isothiocyanate (AITC)
and other reaction products. The major reaction products were allyl thiourea, methyl ester of N-allyl thiocarbamoyl acid and allyl cyanide. A newly identified decomposition product of sinigrin was ethylcyanide. Defatted
Brassica nigra seed meal was treated by the CH3OH/NH3/H2O mixture to simulate the procedure used for rape and mustard seed meal detoxification. suspensions of the meal in the above
mixture of solvents were heated at 20 °C, 40 °C and 60 °C, respectively. The major reaction products were the same as those
arising from sinigrin. Minor products identified were 4-hydroxybenzyl isothiocyanate formed from sinalbin and 2-hydroxy-butenyl
cyanide which arises from progoitrin. In all cases, AITC was very rapidly decomposed. Mechanisms explaining sinigrin decomposition
are presented and discussed.
Received: 3 May 1999 相似文献
11.
Purificación Torrejón María Luisa del Mazo Margarita Tejada M. Careche 《European Food Research and Technology》1999,209(3-4):209-214
Aggregation in minced hake muscle (Merluccius merluccius) during storage at –20 °C was studied in conditions where there is progressive deterioration of functionality and texture
as measured by apparent viscosity and shear resistance. Natural actomyosin was extracted with 0.6 M NaCl over a period of
49 weeks. Insoluble residue was extracted successively with 2% sodium dodecyl sulphate (SDS) and 2% SDS plus 5% β-mercaptoethanol
(ME) solutions. SDS–polyacrylamide gel electrophoresis was performed on the extracted fractions. The results showed a 75%
decrease in 0.6 M NaCl extractability by the end of the storage period. Initially the remaining precipitate was all extracted
in 2% SDS and although the amount extracted in this solution increased as storage time progressed, its proportion decreased,
accounting for as little as 40–50% of the protein aggregate by the end of storage. The proteins most involved in formation
of the aggregate not extracted in 0.6 M NaCl were myosin and actin. Neither of these proteins was fully recovered in the fractions
extracted with 0.6 M NaCl, 2% SDS, or 2% SDS plus 5% ME, and therefore it was inferred that they were forming part of the
aggregates, bound by covalent bonds.
Received: 17 November 1998 相似文献
12.
S. O. Agbeniyi B. Fawole 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1999,208(1):47-49
The effect of curing kola nuts at 30 °C was evaluated at the Cocoa Research Institute of Nigeria, Ibadan, to determine the
effect of curing time and delay between inoculation and initiation of curing on storage rot. For nuts inoculated 24 h prior
to curing, 48–72 h curing at 30 °C gave optimal disease control. The incidence of rot was higher when the treatment was delayed
for 48 h after inoculation. When artificially wounded and inoculated kola nuts were dipped in a solution of 1.0 g l–1 of sodium bicarbonate for 2 mins, disease development was significantly reduced compared to the 0.5% sodium hypochorite treatment.
Sodium metabisulphite also reduced disease development but the level of disease control achieved was not significantly different
from that of the water-dipped controls. The in vivo results were consistent with the in vitro results.
Received: 15 April 1998 相似文献
13.
Stephen Mbithi John Van Camp Raquel Rodriguez Andre Huyghebaert 《European Food Research and Technology》2001,212(2):188-191
Kidney beans (Phaseolus vulgaris) were being processed for inclusion into a weaning food formulation. They were sprouted for 96 h at 30 °C and some nutrients
and antinutrients were evaluated every 12 h. During the entire sprouting period, starch content decreased by 55.6%. This was
accompanied by an increase in reducing and non-reducing sugars from 0.19 to 9.46 and 1.87 to 4.16 g/100 g dry matter (DM)
respectively. These carbohydrate changes were due to an increase in amylolytic activity, as evidenced by a more than fivefold
increase in diastatic activity. Tannins decreased to undetectable levels, and trypsin inhibitor substances and phytates decreased
by 70.7% and 85.9% during the entire sprouting period. In vitro protein digestibility, which is negatively affected by these
antinutrients, increased by 17.1% during the same period. HCl extractability of Ca, Fe and Zn increased by 55.2%, 54.7% and
53.0%, respectively.
Received: 6 March / Revised version: 10 April 2000 相似文献
14.
S. O. Agbeniyi B. Fawole 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1999,10(2):47-49
The effect of curing kola nuts at 30 °C was evaluated at the Cocoa Research Institute of Nigeria, Ibadan, to determine the
effect of curing time and delay between inoculation and initiation of curing on storage rot. For nuts inoculated 24 h prior
to curing, 48–72 h curing at 30 °C gave optimal disease control. The incidence of rot was higher when the treatment was delayed
for 48 h after inoculation. When artificially wounded and inoculated kola nuts were dipped in a solution of 1.0 g l–1 of sodium bicarbonate for 2 mins, disease development was significantly reduced compared to the 0.5% sodium hypochorite treatment.
Sodium metabisulphite also reduced disease development but the level of disease control achieved was not significantly different
from that of the water-dipped controls. The in vivo results were consistent with the in vitro results. 相似文献
15.
L -AAs in 6 M HCl at 100°C. The rate of isomerization on heating in vinegar and aqueous AcOH was aspartic acid (Asp)>serine (Ser)≫proline
(Pro), whereas in 6 M HCl it was Asp>Pro≫Ser. Heating of L-Pro together with glucose and fructose in 5% AcOH at 100°C for 96 h led to the formation of 24% D-Pro relative to L-Pro. From the data it is concluded that high relative amounts of D-Pro detected in matured vinegars are not attributable to acid-catalyzed racemization. In balsamic vinegars high relative
amounts of D-Pro are mainly attributed to the Maillard reaction.
Received: 9 August 1999 相似文献
16.
Thorsten Erbe H. Brückner 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1999,112(2):424-428
Aqueous solutions (5 g/100 ml) of commercial preparations of (a) an enzymatic partial hydrolysate of gelatin and (b) type A gelatin were subjected to threefold heating to boiling in a domestic microwave oven at 750 W and to conventional heating. Then samples were totally hydrolyzed (6 M hydrochloric acid, 110 °C, 24 h) and investigated for the presence of eight possible stereoisomers of 3- and 4-hydroxyproline (Hyp) using capillary gas chromatography. Amino acids were analyzed as N(O)-trifluoroacetyl 2-propyl esters on Chirasil-l-Val and detected by selected ion monitoring mass spectrometry. Blanks of (a) and (b) were analyzed in parallel. Relative amounts of 5.0±0.2% cis-4-d-Hyp were generated from native trans-4-l-Hyp as a result of total hydrolysis in all samples and independent of previous treatment. Notably, neither cis-3-l-Hyp nor cis-4-l-Hyp could be detected in either of the gelatin samples. Thus a report on the generation of antifibrotic and therefore potentially hazardous cis-3-l-Hyp and cis-4-l-Hyp from protein-bonded native trans-3-l-Hyp and trans-4-l-Hyp on microwave heating of infant formulae could not be confirmed. 相似文献
17.
I. M. N. Sousa Elsa C. Matias Olga Laureano 《European Food Research and Technology》1997,205(2):140-142
In this work the production of grape juice jellies with a low methoxyl pectin was studied. Availability of this kind of jelly
will increase the range of dietetic products and is a promising alternative use for grapes surplus to the needs of the enological
industry. The formulation of the jellies was optimized by response surface methodology (RSM), using as independent variables
total sugar content (20 – 50°Brix), low methoxyl pectin content (0.5 – 1.5%) and processing temperature (55 – 90°C) at five
levels. The dependent variable was the overall balance (B), a response obtained from sensory analysis. B was chosen from a series of sensory attributes evaluated by a test panel and the data treated by principal component analysis
(PCA). The resulting polynomial equation (R
2 = 0.92) showed the maximum value for B to occur for a jelly produced with 38°Brix of total sugar, 1.2% of low methoxyl pectin and a processing temperature of 69°C.
The sensory-optimized jelly was objectively characterized for texture and dynamic rheological behaviour.
Received: 2 October 1996 / Revised version: 7 January 1997 相似文献
18.
The effects of temperature fluctuation ranges, number of fluctuations carried out, and packaging during frozen storage on
the texture of potato tissue in terms of compression, shear, and tension rheological parameters were assessed through data
generated according to a factorial design using principal component analysis (PCA). Five ranges of fluctuation (–24 °C to
–18 °C, –18 °C to –12 °C, –12 °C to –6 °C, –24 °C to –12 °C and –18 °C to –6 °C) applied 2, 4, 8, 16, 24, and up
to 32 times on unpacked and pre-packed frozen potatoes, were considered. The controls were unpacked and prepacked frozen tissues
thawed immediately without undergoing any fluctuation. In addition, several geometrical, technological, and chemical parameters
were determined. PCA showed that maximum shear force, Fs was the best rheological parameter for differentiation of the structural damage and softening occurring in the tissue at
each treatment, which was closely related to its duration, TT
d
. PCA did not permit complete discrimination between the five fluctuation ranges, but it clearly separated samples subjected
to –18 °C/–6 °C from those subjected to –24 °C/–18 °C. Frozen samples undergoing up to four fluctuations formed a separate
cluster from those undergoing a higher number. Analysis also clearly separated unpacked from pre-packed samples in response
to slower freezing rates reached in the latter.
Received: 17 December 1999 相似文献
19.
Tumuluru Jaya Shankar Shahab Sokhansanj Sukumar Bandyopadhyay A. S. Bawa 《Food and Bioprocess Technology》2010,3(4):481-490
In the present study, response surface method (RSM) and genetic algorithm (GA) were used to study the effects of process variables
like screw speed, rpm (x
1), L/D ratio (x
2), barrel temperature (°C; x
3), and feed mix moisture content (%; x
4), on flow rate of biomass during single-screw extrusion cooking. A second-order regression equation was developed for flow
rate in terms of the process variables. The significance of the process variables based on Pareto chart indicated that screw
speed and feed mix moisture content had the most influence followed by L/D ratio and barrel temperature on the flow rate. RSM analysis indicated that a screw speed > 80 rpm, L/D ratio > 12, barrel temperature > 80 °C, and feed mix moisture content > 20% resulted in maximum flow rate. Increase in screw
speed and L/D ratio increased the drag flow and also the path of traverse of the feed mix inside the extruder resulting in more shear.
The presence of lipids of about 35% in the biomass feed mix might have induced a lubrication effect and has significantly
influenced the flow rate. The second-order regression equations were further used as the objective function for optimization
using genetic algorithm. A population of 100 and iterations of 100 have successfully led to convergence the optimum. The maximum
and minimum flow rates obtained using GA were 13.19 × 10−7 m3/s (x
1 = 139.08 rpm, x
2 = 15.90, x
3 = 99.56 °C, and x
4 = 59.72%) and 0.53 × 10−7 m3/s (x
1 = 59.65 rpm, x
2 = 11.93, x
3 = 68.98 °C, and x
4 = 20.04%). 相似文献
20.
Marisa S. Garro Graciela F. de Valdez G. Oliver G. S. de Giori 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1999,208(1):57-59
The reduction of soya milk oligosaccharides by Bifidobacterium longum CRL 849 was studied. The utilization of stachyose was concomitant with the use of sucrose. Maximum hydrolysis of stachyose
(49.3%) occurred during the first 7 h of incubation at 37 °C, while a 79.3% decrease in the concentration of sucrose was
observed after 9 h. No raffinose was detected after hydrolysis of the stachyose. Cell population decreased after 8 h of incubation
because of the low pH attained (pH 4.7). l(+)-Lactate concentration was higher than acetate (molar ratio 6.7 : 1) at 6 h followed by a slow increase in acetate formation.
Ethanol was detected in small amounts at the end of the incubation time (24 h).
Received: 29 December 1997 相似文献