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1.
Clement K. Sankat Francois Castaigne & Rohanie Maharaj 《International Journal of Food Science & Technology》1996,31(2):123-135
Ripe banana, cut to 10mm thick slabs were osmotically treated in sugar solutions of 35, 50 and 65° Brix for 36h. The initial moisture content fell from a value of 3.13kg H2 O DM to 2.19, 1.63 and 1.16kg H2 O kg−1 for treatment in the three solutions, respectively. These slabs, with Total Soluble Solids (TSS) contents of 26, 34 and 39° Brix, respectively, as well as freshly cut but untreated slabs (15° Brix) were air dried in a cabinet type tray drier to near equilibrium conditions at fixed temperatures from 40 to 80°C and at a constant air speed of 0.62m s−1 . Drying was found to occur in the falling rate period only for both banana types and two drying constants K1 and K2 were established for a first and second falling rate period of drying. Increasing the drying air temperature significantly enhanced the drying rate and the K-values, except at 80°C when the rates fell, possibly because of case hardening of the slabs. Reducing the slab thickness also improved the drying rate, but increasing the air speed to 1.03m s−1 did not have any profound effect. As the sugar content of the banana slabs increased through the osmotic treatment, drying rates fell. Calculated apparent moisture diffusivities at 60°C ranged from 34.8× 10−10 m2 s−1 (fresh slab) to 8.8×10−10 m2 s−1 for dried (39° Brix) slabs. The moisture diffusivity was significantly lowered as the moisture content dropped in drying and with increased levels of sugar. Previously osmosed and then air dried banana slabs showed appealing colour and texture compared to the fresh banana. 相似文献
2.
ABSTRACT: A visible/near-infrared spectrophotometric method was developed for betacyanin and moisture content in Amaranthus samples. A standard error of prediction (SEP) of 0.25 mg/g for betacyanins ( r 2 = 0.97) and 2.18% for moisture ( r 2 = 0.99) was obtained on the validation sample set. Effect of 5 postharvest treatments on betacyanin degradation was assessed. Freeze-drying and -18°C frozen storage gave over 97% pigment retention, compared to natural air (52.8%), solar drying (63.5%), air oven drying (61.9 to 83.1%), and 14°C storage (78.3%). Air-drying gave the lowest degradation rate and longest half-life among the solar and oven-drying treatments for 8 h. Dried samples showed good pigment stability with 28.6 mo half-life at 25°C. 相似文献
3.
OTONIEL CORZO NELSON BRACHO ANGEL PEREIRA ALBERTO VÁSQUEZ 《Journal of Food Processing and Preservation》2009,33(S1):340-355
The moisture mass transfer parameters characterizing the air drying of coroba slices were determined using the correlation between Biot and Dincet numbers. The air drying was carried out at temperatures of 71, 82 and 93C and velocities of 0.82, 1.00 and 1.18 m/s. Experimental moisture content data for coroba slices were collected. The drying coefficient and lag factor were calculated from the experimental data and were incorporated into the correlation. The moisture diffusion coefficient, Biot number and mass transfer coefficient ranged between 1.147 × 10 − 12 –3.740 × 10 − 12 m2 /s, 0.097–0.114 and 0.903 × 10 − 4 –1.729 × 10 − 4 m/s, respectively. The predicted dimensionless moisture content profiles showed adequate agreement with the experimental observations, with the mean relative error between 0.98 and 4.61%.
As drying is an energy-intensive operation, it has become the prime concern of the researchers to optimize process conditions that lead to energy savings. Moisture transfer parameters are important transport properties needed for accurate modeling in food drying applications. Therefore, accurate determination of these parameters for the drying operation is essential. There is a large amount of studies available in the literature to determine and calculate these parameters for the products subjected to drying. But limited studies have been carried out to determine these parameters using the drying process parameters in terms of lag factor and drying coefficient as first introduced by Dincer and Dost. 相似文献
PRACTICAL APPLICATION
As drying is an energy-intensive operation, it has become the prime concern of the researchers to optimize process conditions that lead to energy savings. Moisture transfer parameters are important transport properties needed for accurate modeling in food drying applications. Therefore, accurate determination of these parameters for the drying operation is essential. There is a large amount of studies available in the literature to determine and calculate these parameters for the products subjected to drying. But limited studies have been carried out to determine these parameters using the drying process parameters in terms of lag factor and drying coefficient as first introduced by Dincer and Dost. 相似文献
4.
Effects of pyro-, tripoly- and hexametaphosphates (0.5 and 1%, w/w) on growth of Staphylococcus aureus strain 196E and enterotoxin A (SEA) production were studied in cooked custard and beef at 22 and 30°C. No effect was observed in custard, where cell numbers/g increased from 103 to 108 and SEA reached 4.2 ng/g after 48 h at 22°C, irrespective of treatment. Cell numbers in cooked beef were ca. 109 /g after 48 h, and reduced numbers (by 1.5–2 log cycles) were found in samples containing 0.5 and 1% pyrophosphate during incubation at 22%, but not at 30°C. SEA concentrations in beef were 28 ng/g after 48 h at 22°C, and 93 and 184 ng/g after 24 and 48 h, respectively, at 30°C. SEA concentration correlated with amount of growth, and was nondetectable when cell numbers were ± 106 /g. Reduction of the meat pH by sodium acid pyrophosphate contributed to the observed inhibitory effect. 相似文献
5.
不同干燥方式对莲子品质的影响 总被引:2,自引:0,他引:2
研究了莲子的热风干燥、真空微波干燥、真空冷冻干燥、热风-真空微波干燥和热风-气流膨化干燥5 种不同干燥方式及其对莲子干燥产品物理性质、主要营养成分和微观结构的影响。结果表明:总色差值大小顺序为真空冷冻干燥>热风-气流膨化干燥>热风干燥>真空微波干燥>热风-真空微波干燥;硬度大小顺序为热风干燥>真空微波干燥>热风-真空微波干燥>热风-气流膨化干燥>真空冷冻干燥,而脆度大小顺序为真空冷冻干燥<真空微波干燥<热风干燥<热风-真空微波干燥<热风-气流膨化干燥;比容大小顺序为真空冷冻干燥>热风-气流膨化干燥>热风-真空微波干燥>真空微波干燥>热风干燥;复水性大小顺序为真空冷冻干燥>热风-气流膨化干燥>热风-真空微波干燥>真空微波干燥>热风干燥;5 种产品中的蛋白质和粗纤维含量相差不大;真空冷冻干燥、热风-真空微波干燥与热风-气流膨化干燥产品的微观结构均观察到明显的蜂窝状结构,热风干燥产品仍为致密结构,真空微波干燥产品中仅出现少量空隙。综合看来,热风-气流膨化干燥可以作为开发莲子休闲食品的适合加工方式。 相似文献
6.
The effects of tree and room ripening and of storage at chill temperatures and at 26–29°C on the sensory quality, composition and respiration of edible wild mango fruits were investigated.
Fruits harvested at the mature green stage and ripened at 26–29°C were slightly preferred to tree-ripened fruits in colour and texture. Apart from a lower moisture content, room-ripened fruits were comparable in composition with tree-ripened fruits. During storage at 26–29°C, CO2 production increased sharply from 22 ml kg-1 h-1 at the end of the first day, reaching a maximum of 91 ml kg-1 on day 5 and declining thereafter; O2 consumption followed a similar trend. The respiratory climacteric coincided with the onset of ripening. Fruits held at 12–15°C developed symptoms of chilling injury including pitting and black spots in mature green fruits, and brownish discoloration, pitting, surface scald, excessive softening and decay in ripe fruits. 相似文献
Fruits harvested at the mature green stage and ripened at 26–29°C were slightly preferred to tree-ripened fruits in colour and texture. Apart from a lower moisture content, room-ripened fruits were comparable in composition with tree-ripened fruits. During storage at 26–29°C, CO
7.
Reduction of Streptococcus thermophilus in a whey protein isolate by low moisture extrusion cooking without loss of functional properties 总被引:1,自引:0,他引:1
C. QUÉGUINER E. DUMAY C. CAVALIER J. C. CHEFTEL 《International Journal of Food Science & Technology》1989,24(6):601-612
A whey protein isolate powder (WPI) (4–5% water) inoculated with 5x105 viable Streptococcus thermophilus per g, was continuously processed in a twin screw extruder under the following conditions (barrel length = 500 or 1000 mm; screw profile = forward transport and compression elements; moisture content during extrusion = 4–5%; feed rate = 10 kg h-1 ; barrel temperature ( Tb ) = 80–204°C; speed of screw rotation = 50 r.p.m.). The minimum residence time determined by pulse injection of erythrosin was 20–25 s (500 mm barrel) or 35–40 s (1000 mm barrel).
Reduction values of viable Streptococcus thermophilus of 104.2 -fold (500 mm barrel, Tb = 143°C) or 104.9 -fold (1000 mm barrel, Tb = 133°C) were obtained without any modification of protein solubility or gelling properties. WPI extruded at the highest barrel temperatures (182–204°C) underwent limited browning and reduction of protein solubility. Gel permeation and hydrophobic interaction chromatography of the soluble constituents did not show any aggregates of β-lactoglobulin or α-lactalbumin.
Gels prepared from control or extruded WPI ( Tb 143°C with a barrel length = 500 mm or Tb 133°C with a barrel length = 1000 mm) were identical, as judged by scanning electron microscopy and rheological evaluations. 相似文献
Reduction values of viable Streptococcus thermophilus of 10
Gels prepared from control or extruded WPI ( T
8.
K. S. JAYARAMAN V. K. GOPINATHAN L. A. RAMANATHAN 《International Journal of Food Science & Technology》1980,15(2):217-226
Quick-cooking dehydrated pulses were made from husked split grains of red gram, black gram and Bengal gram using high temperature short time (HTST) pneumatic drying technique wherein porosity was brought about in the dried pulses by exposure of the cooked grains initially to air at a high temperature (170–200°C) for a short duration (4–6 min) in a laboratory model HTST pneumatic drier followed by finish drying at a lower temperature (60–70°C) in a conventional tray or fluidized bed drier. Optimum temperature and time for the HTST drying of the grains were worked out and the HTST dried products were evaluated with respect to their drying behaviour, rehydration characteristics and shelf stability vis-a-vis the conventional hot air dried products.
Considerable reduction in drying and rehydration times could be achieved by the HTST process. The increase in porosity achieved and the HTST treatment did not adversely affect the shelf stability of the grains to any measurable extent.
The technique involves simple equipment and less capital investment as compared to other methods of drying, such as explosive puffing, achieving the same objective. It is amenable to continuous processing as the time of high temperature drying is very short. 相似文献
Considerable reduction in drying and rehydration times could be achieved by the HTST process. The increase in porosity achieved and the HTST treatment did not adversely affect the shelf stability of the grains to any measurable extent.
The technique involves simple equipment and less capital investment as compared to other methods of drying, such as explosive puffing, achieving the same objective. It is amenable to continuous processing as the time of high temperature drying is very short. 相似文献
9.
Antonio Mulet Miguel Blasco José García-Reverter Josév. García-Pérez 《Journal of food science》2005,70(5):E318-E323
ABSTRACT: Modeling drying kinetics is very useful for optimization purposes. Hot air drying kinetics were carried out in monolayer at different temperatures (60°C, 70°C, 80°C, 90°C, and 100°C) and for different sample types (peeled and unpeeled rhizomes of different sizes). Mathematical models based on Fick's law were used to describe water removal, considering different boundary conditions and geometries. Effective moisture diffusivities identified from modeling presented an Arrhenius-type relationship. An additional mass transfer resistance was identified as due mainly to the peridermis layer (peridermial resistance). The accuracy of the model assuming peridermial resistance only in the radial direction and solved using the finite differences method was illustrated, and the mass transfer coefficient was identified (k = 9.7 × 10-5 kg water/m2 /s). Keywords: Curcuma longa , drying, modeling, peridermial resistance 相似文献
10.
Won-Woo Kim & Byoungseung Yoo 《International Journal of Food Science & Technology》2009,44(3):503-509
Rheological properties of acorn starch dispersions at different concentrations (4%, 5%, 6% and 7%) were evaluated under steady and dynamic shear conditions. The flow behaviours of the acorn starch dispersions at different temperatures (25, 40, 55 and 70 °C) were determined from the rheological parameters provided by the power law model. The acorn starch dispersions at 25 °C exhibited high shear-thinning fluid characteristics ( n = 0.23–0.36). Consistency index (K) and apparent viscosity (ηa,100 ) increased with an increase in starch concentration, and were also reduced with increasing temperature. Within the temperature range of 25–70 °C, the ηa,100 obeyed the Arrhenius temperature relationship with a high determination coefficient ( R 2 = 0.97–0.99), with activation energies (Ea ) ranging between 16.5 and 19.0 kJ mol−1 . Both the power law and exponential type models were employed in order to establish the relationship between concentration and apparent viscosity (ηa,100 ) in the temperature range of 25–70 °C. Magnitudes of storage ( G' ) and loss ( G ") moduli increased with an increase in the starch concentration and frequency (ω). The magnitudes of G ' were higher than those of G " over most of the frequency range (0.63–62.8 rad s−1 ). The dynamic (η*) and steady shear (ηa ) viscosities of acorn starch dispersion at 7% concentration follow the Cox–Merz superposition rule. 相似文献
11.
FABRÍCIO F DE FARIAS WALACE R DA SILVA ANA CAROLINA N BOTELHO IRACEMA M DE C DA HORA GIOVAN KRONENBERGER ADRIANO G DA CRUZ 《International Journal of Dairy Technology》2006,59(4):261-264
The microbiological quality of 60 ice cream samples of three commercial brands (A, B and C) of various flavours, commercialized in some towns in the State of Rio de Janeiro, Brazil, was evaluated. Total bacteria count (TCB), coliforms at 35°C (CT), coliforms at 44°C (CF) and presence of Staphylococcus aureus were performed on all samples. TCB ranged from 2.0 × 10 2 to 6.9 × 10 5 cfu/mL, CT from < 3–≥ 2400 MPN/mL, CF from < 3–1100 MPN/mL and S. aureus from < 10–1.4 × 10 6 cfu/mL. The level of bacterial contamination found in this study reflects the unhygienic conditions prevalent in manufacturing and storage of ice creams. Actions are thus necessary by the Brazilian regulatory agencies to require the ice cream processing plants to adopt quality guarantee systems, such as good manufacturing practices and hazard analysis and critical control points system. 相似文献
12.
不同干燥方式对枣粉品质的影响 总被引:2,自引:0,他引:2
通过对变温压差膨化干燥、真空干燥、热风干燥和真空冷冻干燥4 种干燥方式所得枣粉的物理特性和营养成分的分析测定,研究不同干燥方式对枣粉品质的影响。结果表明:在物理特性方面:真空干燥和真空冷冻干燥枣粉呈现较好色泽,真空冷冻干燥枣粉溶解性差于其他3 种枣粉,吸湿性无明显差异,变温压差膨化干燥和热风干燥枣粉复水性较好,真空冷冻干燥枣粉的粒径和堆积密度最小;在营养成分方面:4 种枣粉的营养成分较鲜样均有不同程度的降低,变温压差膨化干燥和真空冷冻干燥枣粉的还原糖和总糖含量相对较高,真空干燥枣粉总酸含量最高,真空干燥和真空冷冻干燥枣粉的VC和黄酮含量较高,真空冷冻干燥和变温压差膨化干燥枣粉的环磷酸腺苷含量稍高于其他两种。枣粉的综合评分结果显示,真空冷冻干燥枣粉品质最佳,其次是真空干燥枣粉和变温压差膨化干燥枣粉,热风干燥枣粉品质最差。真空冷冻干燥和真空干燥生产成本高,变温压差膨化干燥枣粉品质较好,且所需干燥时间短,生产效率高、成本低,适宜在枣粉加工产业推广。 相似文献
13.
Rapid dye reduction tests have been developed to determine the quality of meat. Three chemical indicators, resazurin and two tetrazolium compounds, were used to correlate the microbial numbers and reduction times in meat samples. Twenty-five surface samples from sheep carcasses were subjected to each reduction test. Total viable counts given were obtained at 37°C. Resazurin reduction time was 90–120 min when the bacterial counts ranged from 1.5×106 to 7.7×106 /cm2 . Samples showing bacterial counts between 1.5×106 and 6.0×106 /cm2 reduced tetrazolium (NBT) in 360–390 min whereas samples containing bacterial counts of 2.1×106 /cm2 took 420–450 min to reduce iodophenyl nitrophenyl tetrazolium (INT) dye. Regression equations relating the number of organisms per cm2 and reduction time were applied to predict the microbiological quality of meat samples from reduction time data. Among the three dyes, resazurin gave the lowest reduction time. 相似文献
14.
Tariq Iqbal Fernanda A. S. Rodrigues Pramod V. Mahajan & Joe P. Kerry 《International Journal of Food Science & Technology》2009,44(7):1408-1414
Investigation of respiration rate of fresh produce, under different gas composition and temperatures, and respective mathematical modelling is central for the modified atmosphere packaging design. This work investigates the effect of temperature (4, 8, 12, 16, 20 °C) and gas composition (O2 between 3 to 21% and CO2 between 0 to 15%) on respiration rate of whole mushrooms. Oxygen and carbon dioxide respiration rates increased significantly (3–4 fold) as the temperature elevated from 4 to 20 °C and were in the range of 13.23 ± 3.12 to 102.41 ± 2.132 mL kg−1 h−1 ) and 14.33 ± 1.56 to 97.02 ± 2.51 mL kg−1 h−1 ) respectively. Low O2 and high CO2 levels reduced O2 consumption and CO2 production rates of whole mushrooms on average by a circa 47–60% at all temperatures as compared to the respiration rate at ambient air. Mathematical models were developed for RO2 and RCO2 , by combining the Arrhenius and Michaelis–Menten uncompetitive equations. These models predicted well, O2 consumption and CO2 production rates of whole mushrooms as a function of both temperature and gas composition. 相似文献
15.
JAMES H. MOY 《Journal of food science》1971,36(6):906-910
SUMMARY— A study was made to develop high Quality juice powders from four tropical fruits. Guava and mango puree, passion fruit and pineapple juice were dehydrated in a vacuum-puff freeze-drying process. Sucrose in amount (25–40%) approximating nectar formulations was mixed with single-strength juice or puree samples, blended 2 min, and frozen. Freezing temperatures of various samples were measured in a constant temperature bath of −21.6°F. Samples initially frozen in blast freezers at −40°F or 0°F with 0.25–1.0 lb/ft2 were vacuum-puffed and freeze dried on aluminum trays at 50μ Hg and 120–130°F shell temperature for 6–9 hr to 1–2% moisture. Puffing was affected by (1) rapid freezing of the juice-sucrose mixture; (2) artificially entrapping some gas in the mixture before freezing; (3) changing the pressure or temperature in the chamber to effect gas expansion; and (4) increasing the mixture viscosity to limit bubble sizes. Results of drying over 160 different samples showed that: (1) added sucrose to give a 40° 5° Brix in the mixture resulted in a stable 'puffed' structure; (2) several permissible calcium salts and silica at 0.1–0.5% (w/w) added to the mixture before drying, improve the free-flowing properties of the dried product. Process variables are discussed and typical sample compositions given. 相似文献
16.
ISABELLE BABIC GHISLAINE HILBERT CHRISTOPHE NGUYEN-THE JOSEPH GUIRAUD 《International Journal of Food Science & Technology》1992,27(4):473-484
Spoilage of ready-to-use grated raw carrots packaged in polymeric films and stored at 10°C was investigated for involvement of yeasts. Cryptococcus albidus was only isolated during the first 3 days of storage, increasing to levels of 105 –106 g-1 . Candida lambica was more commonly isolated after 3–7 days of storage, and reached 107 –108 g-1 after 12 days. Candida sake was present throughout storage, increasing from 105 –106 after 3 days to 107 –108 after 12 days. In some samples, Candida parapsilosis and Candida tropicalis were also isolated at levels similars to C. sake . All the yeasts isolated at the end of storage were fermentative species and their metabolism was characterized with a Warburg apparatus. Neither the number of yeasts nor the composition of the yeast flora were related to the deterioration of the product. Although Candida lambica inoculated on grated carrots caused spoilage after 12 days at 10°C, the high O2 permeable film was most effective in reducing exudate. 相似文献
17.
R. GUZMAN-TELLO J. C. CHEFTEL 《International Journal of Food Science & Technology》1990,25(4):420-434
The thermal and/or oxidative colour loss from a wheat flour/all-trans β-carotene (20–80 mg kg−1 ) mix during extrusion cooking follows first order kinetics. The intensity of processing in extrusion is reflected in the overall rate constant ( K ) of colour loss. K -values were in the range 3–20x10−3 s−1 . They increased markedly with decreasing water content of the mix (24–14%), and with increasing barrel temperature (100–220°C). Results were independent of the type of twin-screw extruder (Werner-Pfleiderer Continua 37 or Clextral BC-45). Modelling of the overall rate constant K and of the 'equivalent plug flow' residence time was used to define 'iso-destructive' extrusion conditions giving approximately the same residence time and the same mean product temperature. Extrusion under N2 or O2 , or in the presence of 1 mg BHT per g of β-carotene, slightly affected colour loss. Adsorption chromatography on alumina indicated that within a barrel temperature range of 125–200°C, 38–73% of the initial all-trans β-carotene was destroyed, and that 2/3 to 1/2 of this loss corresponded to the formation of 9-cis plus 13-cis β-carotene isomers. The formation of smaller amounts of unknown β-carotene derivatives may be responsible for the colour loss. 相似文献
18.
19.
Comparison of high pressure treatment and thermal pasteurization effects on the quality and shelf life of guava puree 总被引:3,自引:0,他引:3
The effects of high pressures and thermal pasteurization on the survival of microorganisms, enzyme inactivation and quality changes of guava puree during storage at 4°C were investigated and compared with untreated samples. After treatment at a pressure of 600MPa and 25°C for 15 min, the microorganisms in guava puree were inactivated to less than 10 cfu mL−1 and the product exhibited no change in colour, pectin, cloud and ascorbic acid content as compared with fresh samples. The inactivation of enzymes in guava puree by thermal pasteurization was greater than by high pressures. The microbial count in guava puree reduced to 200 cfu mL−1 and the product showed marked changes in viscosity, turbidity and colour when heated at 88–90°C for 24s. The content of pectin, cloud and ascorbic acid as well as colour in untreated and high pressurized (400MPa) guava puree gradually decreased, whereas these changes were not observed in pasteurized (88–90°C) and high pressurized (6000MPa) puree during storage at 4°C for 60 days. The guava puree treated at 600MPa and 25°C for 15 min retained good quality similar to the freshly extracted puree after storage at 4°C for 40 days. 相似文献
20.
H. J. SWATLAND 《International Journal of Food Science & Technology》1989,24(5):503-510
Reflectance spectra (400–800 nm) were obtained from the interior of ovine sternomandibularis muscle as temperatures changed between 0 and 80°C by means of optical fibres. Between 0 and 40°C, no significant changes were detected, but between 25 and 80°C reflectance increased (P < 0.001). The temperature coefficient of reflectance (slope/mean) reached maxima at 440 nm (0.065 °C-1 ) and at 560 nm (0.039 °C-1 ), but was fairly uniform for much of the remainder of the spectrum (0.028 °C-1 ). Reflectance started to increase at about 35°C, and decreased between 70 and 80°C. Little evidence for the loss of red and the appearance of brown pigments was detected from estimates of chromaticity coordinates x and y. The major effect of cooking was to increase light scattering (opacity). 相似文献