高温杀菌对麻婆豆腐菜肴食用品质的影响

为研制常温长货架期的豆腐菜肴产品,以麻婆豆腐为对象,研究了不同高温杀菌温度及时间对产品品质的影响,对高温杀菌处理前后的麻婆豆腐进行了失水率、色泽、质构、感官评价等分析,在保证豆腐菜肴杀菌效果(F₀≥4.0)前提下,115、118、121 ℃所对应的适宜杀菌时间分别为28、17、14 min。麻婆豆腐失水率随着杀菌温度上升而增加,与115、118 ℃杀菌条件相比,121 ℃杀菌条件下失水率显著提高。经过杀菌后,豆腐的外部色泽变化较大,其中118 ℃下杀菌后豆腐颜色较好。此外,经过杀菌后,麻婆豆腐的硬度、咀嚼性、胶着性降低,但不同杀菌条件之间并无显著性差异。感官评价结果显示,不同杀菌条件之间并无显著性区别。因此,综合考察杀菌后麻婆豆腐各方面品质变化,确定118 ℃、17 min杀菌对麻婆豆腐效果最佳。     

Preparation of tofu using chitosan as a coagulant for improved shelf-life

The potential of chitosan as a coagulant in commercial tofu preparation was investigated with six chitosans of different molecular weights using various treatments. The following optimum processing conditions for tofu preparation were proposed: chitosan with a molecular weight of 28 kDa; chitosan solution type, 1% chitosan/1% acetic acid; chitosan solution to soymilk ratio, 1 : 8; coagulation temperature, 80 °C; coagulation time, 15 min. However, the sensory quality of tofu was notably improved using a 1 : 1 mixture of 1% acetic acid and 1% lactic acid instead of 1% acetic acid alone as a chitosan solvent. Tofu prepared with chitosan had lower ash and higher protein content than those of commercial products tested. In storage tests, the chitosan‐tofu had a longer shelf‐life, about 3 days, than tofu made with CaCl₂. This added shelf‐life is significant in view of the magnitude (366 000 tonnes year^?1) of tofu produced from commercial tofu plants (1407 plants as of 1998) in Korea.     

壳低聚糖作为豆腐凝固剂研究进展

豆腐凝固剂主要有传统盐卤和熟石膏,及近年发展应用葡萄糖酸内酯,但现有凝固剂制成豆腐货架期均较短;壳低聚糖能使大豆蛋白发生胶凝,具有较强抑菌作用,能有效延长豆腐货架期。该文综述壳低聚糖作为豆腐凝固剂研究进展,分析壳低聚糖替代现有豆腐凝固剂优势及存在难点。     

Physicochemical, Microbiological, and Sensory Evaluation of Minimally Processed Tarocco Clone Oranges Packaged with 3 Different Permeability Films

ABSTRACT: Fruits of 3 Tarocco clones ('Gallo', 'Arcimusa', and 'Scirè') were sliced, packaged with different permeability films, and stored at 4°C for 14 to 15 d to find the best clone for processing and the most suitable packaging conditions to extend the shelf life of these products. Physicochemical parameters of Tarocco oranges slices, packaged with 3 films of different permeability, did not show marked decay phenomena during the storage days. Only a reduction in the ascorbic acid content was observed in almost all the examined clones, especially in products packaged with the most O₂ permeable films. Concerning microbiological contamination, all clones, packaged with the 3 films, showed, until the 12th storage day, a lower number of colony forming units (CFU)/g (≤ 3.6 × 10⁷ CFU/g) for mesophilic viable counts than the 2 microbiological criteria generally used for fresh-cut fruit and vegetables (10⁸ CFU/g for mesophilic viable counts). In fact, for these products it is possible to expect a shelf life longer than 12 to 13 d. Regarding sensory results, it was observed that the minimally processed Tarocco clone slices packaged with the most permeable to O₂ film were the most appreciated.     

EVALUATION OF MICROBIOLOGICAL, PHYSICOCHEMICAL AND SENSORY QUALITIES OF CHITOSAN TOFU DURING STORAGE

Tofu containing both low and high viscosity chitosan was prepared and changes in the microbiological, physicochemical and sensory properties of the tofu during storage were investigated. The colony forming units of mesophilic and psychrotrophic microorganisms in tofu containing high viscosity chitosan were markedly lower during storage than those in the control tofu as well as the tofu containing low viscosity chitosan. The _pH of the tofu samples increased during storage. The L and a values of the tofu, especially the control tofu, increased during storage. In the sensory test, the roasted nutty and beany aromas of the tofu decreased during storage. Instrumental analysis of hardness and chewiness of the tofu decreased during storage. Overall preference for the tofu gradually decreased during storage, but overall preference for the tofu containing high viscosity chitosan scored higher than the other tofu samples.     

Statistical and Kinetic Studies of the Changes in Soybean Quality during Storage as Related to Soymilk and Tofu Making

ABSTRACT:  The objective of this study was to develop statistical equations and kinetic models to describe the changes of soybean quality during storage. Significant correlations ( P  < 0.0001) were found among most of quality attributes including color parameters (Hunter L , a , b , and Δ E ), solid extractability (as expressed by soymilk solids content), soymilk pH and protein content, tofu yield, hardness, and protein content. Regressed linear equations were developed between color indices ( L/L ₀, ΔE ) and soymilk/tofu making properties. Empirical equations were developed to relate soybean color indices ( L/L ₀, ΔE ) and storage conditions including variables of initial moisture content (MC), relative humidity (RH), temperature ( T ), and duration ( t ). Kinetics of the changes in soybean color and extractability during storage at 70% RH and 22 to 40 °C were investigated. The kinetics was well described by zero-order kinetics. The Arrhenius equation adequately described the temperature dependence of the reaction rate constants for all parameters, from which the activation energies and rate constant were obtained. The equations developed in this study provided simple methods to monitor soybean quality and predict quality changes of soybeans during storage at various conditions.     

RELATIONSHIPS BETWEEN SOYBEAN COMPONENTS AND TOFU TEXTURE1

Tofu was prepared from samples of Amsoy 71 and Vinton or Vinton 81 soybeans grown in different environments. Relationships between soybean, soymilk and tofu protein, lipid, phytic acid, calcium, copper and iron were examined. All components except lipid in soybeans were significantly correlated with the same component in soymilk, but only phytic acid, copper and iron were significantly correlated in soybeans and tofu (moist basis). When relationships were examined on a dry basis, soybean and tofu protein were significantly correlated (r = 0.93). Soybean phytic acid was significantly correlated with tofu calcium (r = 0.90). Tofu calcium and hardness (r = 0.73) and springiness (r = 0.83). were significantly related, and tofu protein was significantly related to fracturability (r = 0.75). The higher-protein varieties (Vinton/Vinton 81) generally produced tofu that had a higher protein content and a firmer, more springy texture than that of the Amsoy 71 beans. Phytic acid may preferentially bind the calcium coagulant, altering the curd structure and the yield, composition and texture of the resulting tofu.     

Effect of Soybean Varieties and Growing Locations on the Physical and Chemical Properties of Soymilk and Tofu

ABSTRACT: Soybean varieties and growing location greatly affected the protein content and color of soymilk and the protein content and yield of tofu ( P < 0.05). Protein content of soybeans was the most important affecting factor for the qualities of soymilk and tofu. There were significant correlations between the protein contents of soybeans and soymilks ( P < 0.05). There were also significant correlation between the soybean protein and the total solid content of soymilk (P < 0.05). Tofu moisture content had significant effect on the hardness and yield of tofu (P < 0.05). The correlation between soybean protein and tofu yield was significant at P < 0.05. The protein content and yield of tofu can be predicted by analyzing soybean protein.     

High Oxygen and High Carbon Dioxide Modified Atmospheres for Shelf-life Extension of Minimally Processed Carrots

The impact of high O₂+ high CO₂ modified atmospheres (MA), on the preservation of minimally processed carrots was studied. A combination of 50% O₂+ 30% CO₂ prolonged the shelf life of sliced carrots compared to storage in air by 2 to 3 d. When the carrots received a pre-treatment with a 0.1% citric acid dip and a sodium alginate edible coating prior to packaging, shelf life was extended by 5 to 7 d. Advantages and disadvantages of the proposed MA over previously recommended MA (1% O₂+ 10% CO₂), related to a range of physicochemical and microbiological characteristics of carrots are discussed.     

Microbiological Shelf Life of Pasteurized Milk in Bottle and Pouch

ABSTRACT:  Shelf life of pasteurized milk in Brazil ranges from 3 to 8 d, mainly due to poor cold chain conditions that prevail throughout the country and subject the product to repeated and/or severe temperature abuse. This study evaluated the influence of storage temperature on the microbiological stability of homogenized whole pasteurized milk (75 °C/15 s) packaged in high-density polyethylene (HDPE) bottle and low-density polyethylene (LDPE) pouch, both monolayer materials pigmented with titanium dioxide (TiO₂). The storage temperatures investigated were 2, 4, 9, 14, and 16 °C. Microbiological evaluation was based on mesophilic and psychrotrophic counts with 7 log CFU/mL and 6 log CFU/mL, respectively, set as upper limits of acceptability for maintaining the quality of milk. The microbiological stability for pasteurized milk packaged in HDPE bottle and stored at 2, 4, 9, 14, and 16 °C was estimated at 43, 36, 8, 5, and 3 d, respectively. For milk samples packaged in LDPE pouch, shelf life was estimated at 37, 35, 7, 3, and 2 d, respectively. The determination of Q₁₀ and z values demonstrated that storage temperature has a greater influence on microbiological shelf life of pasteurized milk packaged in LDPE pouch compared to HDPE bottle. Based on the results of this study, HDPE bottle was better for storing pasteurized milk as compared to LDPE pouch.     

PREPARATION OF TOFU GEL BY HIGH-PRESSURE PROCESSING

The potential of high-pressure processing to produce high-quality foods that are microbiologically safe and with extended shelf life has received much attention in the food industry. Tofu is a nutritious and digestible food that is widely consumed in the world. Differential scanning calorimetry analysis indicated that high-pressure processing could denature soymilk protein completely. Soymilk mixed with glucono-delta-lactone, when processed at 500 MPa for 20 min, could form tofu gel with strength. These gels had smooth appearance, homogeneous texture, light-yellow color and less off-flavors. Scanning electron microscopy revealed it had a cross-linked network structure. This provided a novel method for the soymilk and tofu manufacturers to process soymilk for making tofu gels with new properties.

PRACTICAL APPLICATIONS

High-pressure processing is now getting an increasing interest in the food industry. It is a possible alternative to heat treatment. Soy proteins play an important role in food consumption worldwide. Tofu represents one of the major categories of soy foods. The objectives of this study were to investigate the novel method to make tofu with new properties by high-pressure processing. The results will help soymilk and tofu manufacturers to widen the method to make tofu gels.     

Effect of Delayed Icing on the Microbiological Quality of Tropical Fish: Barracudas (Sphyraena barracuda)

ABSTRACT: Effect of delayed icing on the bacteriological quality of a commercially important tropical fish, barracuda ( Sphyraena barracuda ), was studied. Fish obtained from the fish-landing center of Tuticorin, India, were immediately brought to the laboratory and divided into 2 lots. One lot was immediately iced (II) and the other lot was left at ambient temperature (32 ± 2 °C) for 6 h and then iced (DI). Immediate icing extended the shelf life of barracuda by 6 d. In II fish, the total bacterial count increased from 10³ to 10⁶ colony-forming units (CFU)/g; total lactics and total histamine formers appeared on day 7 and 3, respectively, and the total coliforms were very low. While in DI fish, total bacterial count remained at 10⁶ CFU/g. Total lactics, total histamine formers, and total coliforms were high.     

The effect of oyster shell powder on the extension of the shelf life of tofu

The effects of oyster shell powder addition (0%, 0.05%, 0.1% and 0.2% of soy milk) on quality and shelf life of tofu (soybean curd) were investigated. Yield and moisture of tofu prepared with 0.1% of shell powder were higher than that coagulated with a single use of MgCl₂. Syneresis was low when shell powder was added to tofu, but higher when MgCl₂ was added. Shell powder addition (0.05% and 0.2% of soymilk) showed a high level in hardness and gumminess comparing with tofu prepared with a single use of MgCl₂. However, there was no significant difference (p > 0.05) between 0.05% and 0.2% addition of shell powder. When 0.05% of shell powder was added, overall acceptability showed a high score because tofu had a good mouthfeel, moderate firmness and lower beany-flavour. However, there was not a significant difference (p > 0.05) between no addition and 0.05% and 0.1% addition of shell powder. Tofu prepared with shell powder (0.05% and 0.1% addition) had a shelf life of above 2 days longer than that prepared with a single use of MgCl₂. The addition of shell powder (0.05% and 0.1%) for tofu manufacturing resulted in a good sensory evaluation and the extension of shelf life.     

Shelf Life and Microbial Quality of Fresh-cut Mango Cubes Stored in High CO2 Atmospheres

ABSTRACT: Fresh-cut'Carabao'and'Nam Dokmai'mango cubes were stored in air or in high CO₂ atmospheres (3%, 5%, and 10%) at 5 °C and 13 °C. Freshly sliced'Carabao'mango cubes had a lower respiration rate and total bacterial count and higher L-ascorbic acid content and firmness than'Nam Dokmai'mango cubes. The shelf life of fresh-cut mango, based on browning discoloration and water-soaked appearance, was 6 d at 5 °C and 4 d at 13 °C for'Carabao'and 2 d at 5 °C and less than 1 d at 13 °C for'Nam Dokmai'. High CO₂ atmospheres retarded the development of water-soaked'Carabao'cubes at 5 °C and 13 °C and'Nam Dokmai'cubes at 5 °C. Texture of'Carabao'cubes was enhanced by high CO₂, but ethanol and L-ascorbic acid contents were not affected at 5 °C and 13 °C. Total bacterial count was lower in'Carabao'cubes than in'Nam Dokmai'cubes during storage at both temperatures, and a 10% CO₂ only reduced the bacterial count on'Carabao'and'Nam Dokmai'cubes stored at 13 °C. Bacterial flora in'Nam Dokmai'mango cubes consisted mostly of Gram-negative rods assigned primarily to phytopathogenic bacteria such as Pantoea agglomerans and Burkholderia cepacia . The genera of bacteria isolated from cubes stored in 10% CO₂ were similar to those from cubes on the initial day.     

两种工艺生产豆腐的营养成分与品质特性的关系

本研究以12 个大豆品种为原料,分别采用生浆工艺和熟浆工艺制作豆腐,并测定豆腐中的蛋白质及其组分含量、脂肪含量,同时分析豆腐的得率、保水性、色度以及质构特性。在对上述实验结果进行分析整理之后,通过显著性分析得到在豆腐生产过程中,熟浆工艺相比于生浆工艺更具有一定优势的结论,熟浆工艺不仅能够很好地保留大豆中的营养成分,还对豆腐的得率及品质特性有较好的提升。     

Tofu Production from Soybeans or Full-Fat Soyflakes Using Direct and Indirect Heating Processes

We compared processing yield, composition, and quality of tofu from soybeans and from full-fat soyflakes. Tofu was made using a steam-jacketed kettle and a commercial steam-injected cooker. Hydration time was 10 min for flakes and 12h for whole beans. Regardless of cultivar, a higher tofu yield was obtained from the steam-injected cooker system than from the steam-jacketed kettle system. Utilization of flakes required 62--65% less water during soymilk production. Independent of cultivar, tofu produced from full-fat soyflakes was lower in fat (26% d.b.) than whole soybean tofu (40% d.b.).     

Effect of Modified Atmosphere Packaging and Superchilled Storage on the Microbial and Sensory Quality of Atlantic Salmon (Salmo salar) Fillets

ABSTRACT: Fresh Atlantic salmon fillets packaged under modified atmosphere (MA) (CO²:N² 60:40) and air was stored at superchilled (-2 °C) and chilled (+4 °C) temperatures. Changes in sensory scores, microbial growth, headspace gas composition, water loss, and pH were monitored during 24 d of storage. The superchilled MA packaged salmon maintained a good quality, with negligible microbial growth (<1000 colony-forming units [CFU]/g) for more than 24 d based on both sensory and microbial analyses (aerobic plate count, H2S-producing, and psychrotrophic bacteria). Superchilled salmon in air had a 21-d sensory shelf life, whereas MA and air-stored fillets at chilled conditions was spoiled after 10 d and 7 d, respectively.     

Evolution of Quality Characteristics of Minimally Processed Asparagus During Storage in Different Lighting Conditions

ABSTRACT:  The effect of different types of lighting (white, green, red, and blue light) on minimally processed asparagus during storage at 4 °C was studied. The gas concentrations in the packages, pH, mesophilic counts, and weight loss were also determined. Lighting caused an increase in physiological activity. Asparagus stored under lighting achieved atmospheres with higher CO₂ and lower O₂ content than samples kept in the dark. This activity increase explains the greater deterioration experienced by samples stored under lighting, which clearly affected texture and especially color, accelerating the appearance of greenish hues in the tips and reddish-brown hues in the spears. Exposure to light had a negative effect on the quality parameters of the asparagus and it caused a significant reduction in shelf life. Hence, the 11 d shelf life of samples kept in the dark was reduced to only 3 d in samples kept under red and green light, and to 7 d in those kept under white and blue light. However, quality indicators such as the color of the tips and texture showed significantly better behavior under blue light than with white light, which allows us to state that it is better to use this type of light or blue-tinted packaging film for the display of minimally processed asparagus to consumers.     

IDENTIFICATION OF HURDLES FOR IMPROVING STORAGE STABILITY OF BRAISED KIDNEY BEANS, A KOREAN SEASONED SIDE DISH

The aim of this study was to identify factors affecting the preservation of braised kidney beans, a traditional Korean side dish, to extend its shelf life. The effects of ingredient formulation, refrigerated storage and modified atmosphere packaging on storage stability and/or sensory quality were examined. Count of yeast/mold was selected as a primary quality index from the storage test at 10C. A formulation was found in cooked kidney beans, sugar, soy sauce and corn syrup to provide the retarded microbial growth and affordable sensory quality. The temperature dependence value (Q₁₀) for the shelf life of the stretch-wrapped product was 2.0 for temperatures of 5 to 20C. Modified atmosphere packaging (60% CO₂/40% N₂ or 100% CO₂) extended the shelf life at 10C by 500% (to 36 days) compared to air packaging (6 days) based on criteria of yeast/mold growth. Equations for estimating microbial spoilage and shelf life were derived as function of temperature.

PRACTICAL APPLICATIONS

Microbial growth retardation by ingredient formulation change, chilled storage and high CO₂ modified atmosphere packaging is useful to design the processing, packaging and distribution of the Korean side dish product. Quality change kinetics of yeast/mold growth established can be used for determining shelf life of the product under different storage temperature conditions. Through the scale-up procedure, the knowledge found in this study will be useful for the industrial processing and storage of the seasoned side dishes.