Reduction in the pH of vegetables by vacuum impregnation: A study on pepper

A method to decrease pH value in pepper slices employing vacuum was studied. The effects of relaxation time (10, 15 and 30 min), vacuum level (200 and 400 mbar) and vacuum application period (2 and 5 min) were evaluated. Results showed that vacuum impregnation (VI) with lactic acid solution increased the acidification degree to a greater extent than processing carried out at atmospheric pressure. In particular, samples treated at 400 and 200 mbar and submitted to a relaxation period of 30 min, showed a reduction in pH ratio (RpH) from 0.929 to 0.894. Otherwise, samples submitted to conventional dipping at atmospheric pressure showed a RpH of 0.968. Vacuum level was found to be the most important variable influencing the variations in total mass and pH. Vacuum impregnation led to an increase in diffusion rate of hydrogen ions into the vegetable tissue due to the increase in contact area between acid solution and cells. Moreover, a direct correlation between pH reduction on the one hand, and vacuum application period and relaxation time on the other, was observed. Results proved that vacuum impregnation process is a useful technique to improve acidification treatments of vegetables.     

利用乳清制品生产钙强化食品

<正> 世界卫生组织(WHO)表示在众多营养缺乏症中,增长较快的有钙缺乏症和骨质疏松症。此外,骨质疏松症世界代表大会又预测,未来50年因骨质疏松症而导致骨折的病例将增加100％。随着世界性人口老化的增加和因骨质疏松症而引起的脊骨骨折和髋部     

真空浸渍技术在改善果蔬采摘后的品质特性中的应用进展

针对真空浸渍技术在改善果蔬采摘后的品质特性中的应用及作用原理,以及该技术近些年的研究现状和进展进行了详细综述,为该技术在果蔬采摘后的进一步应用研究提供了参考。     

The influence of vacuum impregnation on the fortification of apple parenchyma with quercetin derivatives in combination with pore structures X-ray analysis

The study aim was to investigate the vacuum impregnation (VI) technique for apple enrichment with quercetin glycosides from apple peel. Beside the determination of the quercetin content, structural effects on the apple parenchyma were analyzed by computerized microtomography (μCT). VI was an efficient method to enrich apples with quercetin derivatives which was affected by the apple cultivar, the vacuum pressure, the soluble solid concentration (SSC) and the viscosity of VI solution. After VI of 13 apple cultivars the quercetin content varied between 368 and 604 μg/g dry mass and correlated with the firmness of the native apple and the increased apple weight. The use of low SSC solution resulted in increased quercetin enrichment in contrast to apple pectin solutions with elevated viscosity. The μCT analyses demonstrate that VI was more effective in the inner apple sections than in the outer parts. The study indicates that differences of pore size and microstructure within the apple cortex substantially affected the enrichment process.     

Development of probiotic-enriched dried fruits by vacuum impregnation

In this study an attempt is made to combine the beneficial effects of probiotics with fruit and vegetables by applying the vacuum impregnation process. Apple cylinders were impregnated either with commercial apple juice containing Saccharomyces cerevisiae, and with whole milk or apple juice containing 10⁷ or 10⁸ cfu/ml of Lactobacillus casei (spp. rhamnosus). Impregnated apple samples contained around 10⁷ cfu/g. In order to increase stability and to assure fruit preservation, impregnated apple samples were air dried at 40 °C to a water content of 0.037 kg water/kg dry matter and stored at room temperature for two months. The content of L. casei viable cells in dried and stored product was greater than 10⁶ cfu/g. This concentration level of probiotics is similar to that in commercial dairy products.     

Iron enrichment of whole potato tuber by vacuum impregnation

The effect of vacuum time, restoration time, steam-cooking and storage at 4 °C on the iron content of vacuum-impregnated (VI) whole potato was evaluated. Whole potato tubers were immersed in a 0.4 g/100 g iron (ferric pyrophosphate) solution. Vacuum pressure of 1000 Pa was applied for 0–120 min, and atmospheric pressure restoration for 0–4 h. The result indicated that the iron content of VI potatoes increased with vacuum and restoration time; 1 h vacuum-treatment potatoes provided 6.4 times higher iron content compared to raw potatoes, and 3 h restoration time supplied 6.4 times higher iron content (>4.1 mg/100 g fr.wt.) compared to raw potatoes. Moreover, VI-cooked unpeeled or peeled potatoes had 6 times higher iron content than un-VI-cooked unpeeled or peeled potatoes. European daily potato consumption (260 g) of the VI-cooked unpeeled and peeled potatoes provided adult men with 93–104% and 67–90% of the recommended daily allowance (RDA) of iron, respectively. Also, the daily potato consumption of the unpeeled and peeled potatoes could supply adult women with 43–48% and 31–41% of the RDA, respectively. This study indicated that VI treatment of whole potato was useful for enriching the iron content.     

Proteolysis in Manchego-type cheese salted by brine vacuum impregnation

A new salting procedure based on the brine vacuum impregnation of porous products was tested on Manchego-type cheese and compared with conventional brine immersion. Its effect on cheese proteolysis throughout a 90-d ripening period was determined. Three cheese regions were evaluated (the rind, the middle, and the internal regions). The parameters analyzed were total N, water-soluble N, soluble N in trichloroacetic acid and soluble N in phosphotungstic acid by using the Kjeldahl method, casein profile by urea-PAGE, and peptide profile of the water soluble nitrogen extract by reverse-phase HPLC. Free amino acid formation was monitored with a spectrophotometric method by using a Cd-ninhydrin reagent. Globally, proteolysis was significantly affected by ripening stage (increasing throughout all the maturation period studied) and cheese region (rind showed a proteolysis pattern different from the middle and internal regions). The salting procedure only affected cheese proteolysis in the rind, whereas conventional brine-salted cheeses showed lower proteolysis than vacuum-impregnated cheeses.     

茭白接种-真空浸渍快速发酵新工艺

研究了一种接种与真空浸渍相结合的茭白发酵新工艺。由单因素试验初步确定温度、盐水浓度和接种量3个因素的水平范围,通过Box-Behnken设计及响应面法优化茭白发酵条件,同时测定菌落总数、乳酸菌总数和脆度值,结合感官评定方法,比较该工艺与传统工艺产品品质的差异。结果表明:在25.3℃、NaCl质量分数为4.9%的盐水中和接种量6.0%的条件下,经真空厌氧发酵而成的产品效果最好,生产周期为3 d,菌落总数为7.1×107CFU/mL,乳酸菌总数为5.8×107CFU/mL,脆度值为0.861 9 kg,感官评分为91;以传统工艺发酵生产茭白,生产周期为7 d,发酵成熟时产品菌落总数为19.2×107CFU/mL,乳酸菌总数为3.1×107CFU/mL,脆度值为0.560 8 kg,感官评分为83。接种结合真空浸渍发酵缩短了发酵茭白的生产周期,改善了发酵过程中乳酸菌总数和菌落总数的比例,同时无汁液浸泡的发酵过程也缓解了发酵蔬菜组织软化,使产品保持更好的脆度。     

蔬菜真空预冷实验分析

针对白菜、萝卜、土豆三种蔬菜,进行了真空预冷实验,分析了真空室内压力、蔬菜大小、蔬菜表面洒水等因素对蔬菜真空预冷的影响,为真空预冷工艺改进和预冷技术的推广应用提供参考。     

Improving color stabilization in thermally modified wood by pretreatment with aluminum sulfate vacuum impregnation

The poor anti-weathering performance of thermally modified wood often influences the appearance and service life of wood exposed to an outdoor environment. In this study, wood samples exhibiting ultraviolet (UV) resistance were successfully fabricated by joint aluminum sulfate (Al₂(SO₄)₃) impregnation and thermal modification, and the samples were subjected to accelerated weathering reaching 144 h. Time–dependent changes in the surface color of the control samples and treated samples during weathering were evaluated. Chemical and morphological alterations were analyzed by UV spectrophotometry, attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results showed that incorporating Al₂(SO₄)₃ into the specimens helped prevent both the photooxidative degradation of lignin and the formation of degradation products. The anti-weathering performance of thermally modified wood pretreated by Al₂(SO₄)₃ impregnation improved because the negative effects of ultraviolet light and water on the wood surface were controlled by the high temperature resistance and encapsulation of the hydrolyzed aluminum flocs. The thermal stability also improved in the impregnated–thermally modified samples, as confirmed by the TG results.

     

Effectiveness of antibrowning agents applied by vacuum impregnation on minimally processed pear

Different isotonic solutions containing antibrowning compounds (EDTA, 4-hexylresorcinol, citrate and ascorbate), combined or not with calcium lactate, were applied to minimally processed (MP) pear samples (cv. Blanquilla) by using the vacuum impregnation (VI) technique in order to reduce enzymatic browning. Vacuum impregnated samples were packaged and colour, mechanical properties, development of respiration gases and volatiles in the package headspace and microbial counts were monitored throughout storage at 4 °C. VI treatments with ascorbate solutions and calcium lactate were the most effective to extending the shelf life of MP pear. These treatments caused fewer changes in colour, mechanical properties and volatile composition and slowed microbial growth. Calcium lactate led to a better preservation in terms of mechanical parameters but had minor effects on colour development during cold storage.     

真空浸渍辅助L-半胱氨酸对鲜切马铃薯多酚氧化酶活性的抑制作用

为研究真空浸渍辅助L-半胱氨酸(L-cysteine,L-cys)处理对鲜切马铃薯多酚氧化酶(Polyphenoloxidase,PPO)活性的抑制作用,首先通过单因素试验,考察真空时间(t_1)、浸渍时间(t_2)、L-cys浓度对PPO活性的影响效果,然后采用响应面Box-Behnken中心组合法分析了各个响应因素之间的交互作用对PPO活性的影响,并建立了回归方程预测模型。结果表明,各单因素对PPO活性均有显著的抑制作用,最佳条件分别是:t_1为12 min、t_2为4 min和L-cys浓度为1.2 g/kg。响应面分析法得到的优化条件参数是t_1为740 s,t_2为250 s及L-cys浓度为1.06 g/Kg时对PPO活性的抑制效果最佳。在此条件下所得PPO活性为99.75 U,与理论值97.2539 U的相对误差在2.5%左右。证明此模型具有较好的拟合度,可以预测抑制鲜切马铃薯PPO活性的最佳真空浸渍条件。     

Microstructure and vacuum impregnation response of citrus peels

Vacuum impregnation (VI) technique represents a good choice for developing high quality peel products or food ingredients, taking advantage of their interesting composition, increasing their sweetness and improving their sensory acceptance. Vacuum impregnation response of citrus peels (orange, mandarin, lemon, grapefruit) were analysed using different isotonic solutions. Sample deformation and impregnation levels in line with pressure changes have been determined. Peel microstructure has also been analysed (by Cryo-SEM) before and after the VI process. Results reflect a high capacity of impregnation (45–70% of initial sample volume) and swelling (12–33% of initial sample volume) of the peels. The great porosity of the albedo zone is responsible for this behaviour. In this zone, the great intercellular spaces can be flooded by an external solution, and this makes the citrus peels highly suitable to obtain new products with improved functionality and sensory acceptance.     

Free fatty acid content of Manchego-type cheese salted by brine vacuum impregnation

A new salting method based on the brine vacuum impregnation of porous products was tested in Manchego-type cheese in order to assess its effect on cheese lipolysis during ripening. This new salting method would allow a faster salt diffusion and a more homogeneous initial salt distribution, and would reduce the disposal of brine. Salt-in-moisture content was evaluated in three different cheese zones during a 90-day ripening period in order to monitor salt penetration in the cheese. Lipolysis was evaluated by means of gas chromatography of individual free fatty acids in the medium and internal zones of both cheeses salted by the conventional and the new salting procedures. Free fatty acid concentration regularly increased during ripening. Short-chain free fatty acid content was higher in the internal zone of conventionally salted cheeses than in the internal and medium zones of vacuum impregnated cheeses from the first month after manufacturing, probably due to the low initial salt concentration achieved in the inner zone of conventionally salted cheeses, which can enhance both bacterial and indigenous lipase activity. Panelists considered that conventionally salted cheeses presented a more intense aroma than vacuum impregnated cheeses, though no differences in global flavor intensity were observed.     

Quality and antioxidant capacity of fresh‐cut apple wedges enriched with honey by vacuum impregnation

The effect of vacuum impregnation (VI) of fresh‐cut apple wedges with honey, in presence and absence of a browning inhibitor on physicochemical, sensory and antioxidant properties over 7 days of storage at 2–4 °C was studied. Infusion of wedges with honey resulted in very little weight change indicating loss of internal water and ingress of honey carbohydrates into the wedges, hence the correlation coefficients with soluble solids content (r = ?0.91) and dry matter (r = ?0.77). Water infused samples showed the highest water uptake resulting in an increase in weight of 30%. Browning (P < 0.001) and firmness (P < 0.001) of apple wedges were the quality parameters most affected by VI. Samples dipped in browning inhibitor prior AS1 showed slightly better performance than undipped wedges with regard to browning and firmness. Total phenol content and antioxidant activity were significantly (P < 0.001) lower for honey infused apple wedges.     

Natural colorant enrichment of apple tissue with black carrot concentrate using vacuum impregnation

Coloured apple discs containing black carrot concentrate (BCC), calcium lactate and lactic acid were formulated and produced as a new functional fresh fruit product using vacuum impregnation. Sensory test was conducted to select the most preferred impregnation formulation containing an addition of 0.0%, 0.4%, 0.8% and 1.2% BCC, 1.5%, 3.0% and 4.5% calcium lactate and 2.0%, 3.0% and 4.0% lactic acid. Results indicated that the formulation with the addition of 3% Ca‐lactate, 3% lactic acid and 0.8% BCC within 0.2 m mannitol solution was significantly preferred. The optimum vacuum pressure (211 mm Hg), vacuum time (3 min) and restoration time (20 min) according to highest colorant transfer, while the minimum cellular disruption occurs were estimated using response surface methodology. The use of Ca‐lactate and BCC contributed the treated apple to resemble untreated apple properties in terms of texture, total phenolic, total flavonoid contents and antioxidant capacity.     

Experimental determination of the dynamics of vacuum impregnation of apples

ABSTRACT:  Vacuum impregnation (VI) is a food processing method by which air and native solution are removed from porous spaces within a food and replaced by an external solution. In this study, an experimental device based on a previous design was built, including some modifications, in order to investigate the dynamics of the VI process. The device measured the net force exerted by a food sample submitted to the VI process using a load cell. The influence of the vacuum level and sample geometry was well quantified by the experimental procedure and the modified equipment using apple samples (Fuji var.) as a food model. The results indicated that the experimental device proposed in this study, together with the suggested procedure, is a useful tool to investigate the dynamics of VI processes. It is robust and versatile, and has the advantage of not requiring the determination of the water evaporated during the VI process in a separate experiment, which represents an increase in the accuracy of the results.