模拟胃液条件下苹果多酚对亚硝酸盐的清除作用

在模拟人体胃液的条件下,以亚硝酸盐清除率为指标,比较苹果多酚、茶多酚及VC对亚硝酸盐的清除效果,同时研究苹果多酚不同作用时间对亚硝酸盐清除效果的影响。结果表明：在模拟胃液条件下：苹果多酚、茶多酚及VC均能不同程度地清除亚硝酸盐,且在低质量分数下,清除率随质量分数增加呈对数曲线上升,增加到一定质量分数后清除率变化不大;在低质量分数(0.01%～0.02%)下,苹果多酚的清除率略低于茶多酚,质量分数≥0.03%时,苹果多酚的清除率要高于茶多酚;苹果多酚的清除能力最高可达(98.2±1.3)%,而茶多酚(94.7±0.2)%,VC为(88.6±1.0)%;苹果多酚和茶多酚复配使用的清除效果明显优于单独使用,清除率可达(92.6±0.3)%;苹果多酚和VC复配使用的清除效果优于单独使用,清除率可达(65.7±0.3)%;苹果多酚、茶多酚及VC复配使用时的清除率可达(90.7±0.3)%,比苹果多酚和茶多酚混合使用的效果差,但优于苹果多酚和VC的复配效果;苹果多酚对亚硝酸盐的清除率随作用时间延长而上升,当作用时间达到2h时清除率最高,可达(98.7±0.2)%,时间继续延长,清除率有下降趋势。因此,苹果多酚作为一种天然提取物,在胃酸条件下对亚硝酸盐具有良好的清除作用。     

流动注射化学发光测定苹果多酚抗氧化活性

用流动注射化学发光法测定苹果多酚的体外抗氧化作用。将苹果多酚提取液加入3种化学发光体系,测量其发光强度,根据系统化学发光被抑制的程度评价苹果多酚对活性氧自由基的清除能力,并以抗坏血酸(VC)为阳性对照。结果表明,苹果多酚对三种活性氧自由基(O2-·、·OH、H2O2)的清除能力远强于VC;对H2O2和·OH的清除能力相当,强于对O2-·的清除能力。结果显示苹果多酚具有很好的抗氧化能力。     

Combined treatment of high pressure and heat on killing spores of Alicyclobacillus acidoterrestris in apple juice concentrate

Alicyclobacillus acidoterrestris, a thermoacidophilic and spore-forming bacterium, has been isolated from spoiled acidic juices and is considered to be one of the important target microorganisms in quality control of acidic canned foods. Combined high pressure and heat treatment showed an effectiveness to control A. acidoterrestris spores. However, the effectiveness of the combined treatment may change upon the apple juice concentration. Therefore, the objective of this study was to evaluate different levels of apple juice concentrate for reduction of Alicyclobacillus spores by high pressure and heat. Spores of A. acidoterrestris were inoculated into three different concentrations of apple juice (17.5, 35, and 70 degrees Brix), and subjected to three high-pressure treatments (207, 414, and 621 MPa) at four different temperatures (22, 45, 71, and 90 degrees C). High-pressure treatment (207, 414, and 621 MPa) at 22degrees C did not reduce the level of spores regardless of the apple juice concentration (P > 0.05). In diluted apple juice (17.5 degrees Brix), the combined treatment of high pressure and heat resulted in spore reductions of about 2 log at 45 degrees C, and more than 5 log at higher temperatures (71 and 90 degrees C) in a high-pressure and temperature-dependent manner. For apple juice with a higher concentration (30 degrees Brix), high-pressure treatment showed no effect at 45 degrees C but resulted in about 2 and 4 log reduction at 71 and 90 degrees C, respectively. However, for apple juice concentrate (70 degrees Brix), treatment with heat or high pressure alone, or their combinations showed no inactivation against spores of A. acidoterrestris. It is likely that differences in the water availability explain the greater resistance of spores to high-pressure inactivation in the juice concentrates than in diluted juices. Our results demonstrate that the effect of high pressure combined with heat against spores of A. acidoterrestris was highly dependent on the apple juice concentration.     

Physical and antibacterial properties of edible films formulated with apple skin polyphenols

Fruit and vegetable skins have polyphenolic compounds, terpenes, and phenols with antimicrobial and antioxidant activity. These flavoring plant essential oil components are generally regarded as safe. Edible films made from fruits or vegetables containing apple skin polyphenols have the potential to be used commercially to protect food against contamination by pathogenic bacteria. The main objective of this study was to evaluate physical properties as well as antimicrobial activities against Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella enterica of apple skin polyphenols at 0% to 10% (w/w) concentrations in apple puree film-forming solutions formulated into edible films. Commercial apple skin polyphenol powder had a water activity of 0.44 and high total soluble phenolic compounds and antioxidant capacity (995.3 mg chlorogenic acid/100 g and 14.4 mg Trolox/g, respectively). Antimicrobial activities of edible film containing apple skin polyphenols were determined by the overlay method. Apple edible film with apple skin polyphenols was highly effective against L. monocytogenes. The minimum concentration need to inactive L. monocytogenes was 1.5%. However, apple skin polyphenols did not show any antimicrobial effect against E. coli O157:H7 and S. enterica even at 10% level. The presence of apple skin polyphenols reduced water vapor permeability of films. Apple skin polyphenols increased elongation of films and darkened the color of films. The results of the present study show that apple skin polyphenols can be used to prepare apple-based antimicrobial edible films with good physical properties for food applications by direct contact.     

Thermoaciduric Clostridium pasteurianum spoilage of shelf-stable apple juice

Clostridium pasteurianum BB, a saccharolytic and spore-forming obligate anaerobe, was isolated and identified from shelf-stable apple juice that was responsible for multiple large spoilage outbreaks. The growth and sporulation conditions of C. pasteurianum were atypical compared with those previously published. C. pasteurianum spores were heat resistant in apple juice at pH 3.80, with D-values at 80, 85, and 90°C being 34.4, 15.9, and 4.4 min, respectively, and a z-value of 11°C. The survival curves for thermal inactivation obeyed linear first-order kinetics. Apple juice with varying pH values was used to determine the effect of pH on germination capability of C. pasteurianum spores. The spores were found to be able to germinate at pH as low as 4.3 in pH-adjusted apple juice at low contamination levels. It was confirmed by PCR that C. pasteurianum isolated from spoiled apple juice did not contain the genes for botulinum toxins B and E, which were more commonly found in neurotoxigenic butyric clostridia. Control of finished-juice pH to below 4.0 in combination with mild heating was proposed to prevent potential spoilage of shelf-stable apple juice made with spore-contaminated apple juice concentrate.     

Effect of pH,heat, and light treatments on the antioxidant activity of sweet potato leaf polyphenols

In the present study, the antioxidant activity of sweet potato leaf polyphenols was measured, and the effect of different pH values (3.0, 5.0, 7.0, and 8.0), temperatures (55, 65, 80, and 100°C), and light treatments on sweet potato leaf-polyphenols was investigated. Results showed that the O₂^? scavenging activity of sweet potato leaf polyphenols from cultivar Jishu No. 04150 was 5.84 and 6.20 times of that of tea polyphenols and grape seed polyphenols, respectively, at the concentration of 20 μg/mL. The oxygen radical absorbance capacity was 1.28 and 1.27 times of that of tea polyphenols and grape seed polyphenols, respectively. Sweet potato leaf polyphenols dissolved in pH 5–7 solutions showed higher retention rates of antioxidant activity. Heat treatment at 50 and 65°C and light treatment had little effects on sweet potato leaf polyphenols. In conclusion, sweet potato leaf polyphenols possessed high antioxidant activity and processing stability, having the potential to be a new type of natural antioxidant.     

The effect of pH on the thermal resistance of Clostridium sporogenes (PA 3679) in asparagus purée acidified with citric acid and glucono-delta-lactone.

The influence of type of acid, pH and temperature on heat resistance of Clostridium sporogenes (PA 3679) spores were investigated in white asparagus pureé acidified with citric acid and glucono-delta-lactone (GDL). The pH values studied were: 4.5, 4.8, 5.1 and 5.4 at temperatures of 110, 115, 118 and 121 degrees C. The addition of citric acid and GDL to reduce pH significantly diminished heat resistance of the spores. The two acids investigated differed in their effect on heat resistance at the various pH-levels. The most pronounced effect was observed at the lower heat treatment temperatures investigated. The z values ranged from 10.24 to 13.09 degrees C in the asparagus purée with acids added and with significant differences between the two acids and the various pH levels.     

A STUDY OF PRESTORAGE HEAT TREATMENT EFFECT ON APPLE TEXTURE: DESTRUCTIVE AND NONDESTRUCTIVE MEASUREMENTS

Effects of prestorage heat treatment on the texture of three apple cultivars: 'Gloster,'Golden Delicious' and 'Jonagold' (Malus domestica Borkh.) were studied before and after heat treatments at different time-temperature combinations. Changes of apple firmness, extractable juice content, background color, soluble solids concentration (SSC) and pH values were determined after 4 months cold storage (2C, 95% RH). Prestorage heat treatment can inhibit 'Golden Delicious' softening during cold storage but less effective for 'Jonagold' apples. Severe internal browning was found for heat treated 'Gloster' apples after cold storage. Heat treatments had no benefit on apple juiciness maintenance. Heat treated apples showed more physiological disorders compared with the nontreated apples after 4 months cold storage. The effect of prestorage heat treatment seems to be cultivar dependent.     

EFFECT of HEAT TREATMENT ON FIRMNESS of APPLES and APPLE SLICES

Effects of heat treatment on firmness of apples (Golden Delicious, McIntosh and Delicious) and apple slices were studied. Heat treatment (45C, for 1.75 h) of Golden Delicious and Delicious apples significantly increased their firmness, but no significant increase was observed for the McIntosh cultivar. After storage for 7 days at 2C, the treated apples were firmer than those stored at 10, 18, and 25C. Apple slices prepared from the heat treated apples were also firmer at 21 days storage than those prepared from nontreated apples: differences ranging from 12% for McIntosh to 48% for Delicious. This beneficial firming effect of heat treatment might have application in producing high quality minimally processed slices from Golden Delicious and Delicious apple cultivars.     

The potential application of vanillin in preventing yeast spoilage of soft drinks and fruit juices

The preservative effect of vanillin, the major constituent of vanilla beans, was studied in an apple juice and peach-flavored soft drink. Vanillin activity was tested against Saccharomyces cerevisiae and Candida parapsilosis at 8 and 25 degrees C over an 8-week storage period. Initial results in laboratory media indicated minimum inhibitory concentration values of 17 and 9 mM vanillin for the two yeast strains. Concentrations of 20 and 10 mM vanillin, respectively, were required to achieve complete inhibition of both yeast strains inoculated at a level of approximately 10(4) CFU/ml in the apple juice and peach-flavored soft drink over the 8-week storage at 25 degrees C. These effective levels were reduced to 5 and 1 mM, when the storage temperature was reduced to 8 degrees C. A biocidal effect against both yeasts was observed within 96 h to 8 weeks, with vanillin concentrations of 5 to 40 mM depending on the beverage and the storage temperatures used. The increased activity of vanillin in the peach-flavored soft drink (pH 3.1) in comparison to the apple juice (pH 3.5) is probably a result of the lower intrinsic pH of the former; however, variation in vitamin and mineral levels or the presence of other phenolic compounds between the two drinks might also have contributed to the observed differences. Furthermore, the increased activity at the lower temperature could be linked to the combination of the increased membrane fluidity and the membrane-perturbing action of vanillin. We conclude that vanillin has the potential to preserve fruit juices and soft drinks that are low in both lipid and protein content against S. cerevisiae and C. parapsilosis.     

Changes in Apple Juice Flavor Compounds During Processing

Apple juice flavor fractions were collected at several stages during a commercial process. Replicated experiments were designed to collect samples from untreated pulp, from enzyme treated pulp, after pectinase treatment, after microfiltration (MF), and after pasteurization. Additional juice heating experiments were carried out. Six apple juice flavor compounds were identified based on to retention times and reported studies. The flavor profile changed at the different stages of the production line. Temperatures used (～57.2°C) for enzyme activation and MF tended to increase flavor compounds in apple juice except iso-butyl acetate. The higher temperatures used (～85°C) for pasteurization decreased all flavor compounds except propyl butyrate which increased. Results indicate apple juice may contain heat activated precursors of identified flavor compounds.     

Apple volatiles monitoring and control in microwave drying

Apple volatiles were online monitored with a zNose™ during microwave drying. The samples were first dried at three fixed temperatures of 60 °C, 70 °C, and 80 °C. Four typical volatile peaks were recorded every 4 min for all the three replicates. Apple samples could be dried in a shorter time at high temperatures but were more susceptible to burning. A fuzzy logic controller was then designed and employed to control the drying process. The controller used online detected apple volatiles and burning signals as variables and tried to retain apple volatiles, avoid burning, shorten drying time, and save energy. Based on the temperature curve achieved under fuzzy logic control, a simple linear control method was further developed where zNose™ online assistance could be omitted. Color and sensory evaluation by an untrained taste panel were performed after rehydration. With the new control strategies, apple color and overall appearance were intact and less time and energy were consumed.     

Effect of heat treatment on physiochemical,colour, antioxidant and microstructural characteristics of apples during storage

Changes in qualities of ‘Red Fuji’ and ‘Golden Delicious’ apples in response to different heat treatments (45 and 60 °C) following cold storage were investigated. Quality indices including firmness, titratable acidity, total phenolic content, antioxidant capacity, colour parameters and microstructure were measured. Results indicated heat treatment at both temperatures for 3‐h hastened loss of titratable acidity in ‘Red Fuji’ and ‘Golden Delicious’ apples, but maintained firmness in both cultivars. However, heat treatment at lower temperature (45 °C) best maintained total phenolic compounds and antioxidant capacity in ‘Red Fuji’ apples throughout storage, whereas there was no difference between heat treatments in ‘Golden Delicious’ apples. Examination by scanning electron microscope (SEM) revealed that the effect of heat treatment at different temperatures on ‘Red Fuji’ and ‘Golden Delicious’ apples was structurally different. Apple tissue that had been heat treated at elevated temperature (60 °C) for 3 h was associated with fractured cell walls and collapse of cells.     

苹果汁中维生素C热降解动力学研究

为了探索温度对苹果汁中维生素C降解的影响以及维生素C的降解动力学规律,采用可逆的一级反应模型,对加热温度30、40、50、60、70℃条件下苹果汁中还原型维生素C(AA)和氧化型维生素C(DHA)含量的变化及降解动力学进行了研究,结果表明:60℃的AA反应速率最大,DHA反应速率基本随着温度升高而增大;温度升高,可逆反应速率常数增大,其它降解途径速率常数变化不明显;AA无氧氧化速率与温度有一定关系,50℃的AA无氧氧化速率最大,70℃的AA无氧氧化速率最小;AA和DHA热降解反应活化能均低于一般化学反应活化能,说明苹果汁中维生素C热稳定性较差。维生素C的降解主要是有氧氧化反应,苹果汁中维生素C无氧降解速率比有氧降解速率慢;温度升高,苹果汁中维生素C有氧降解速度加快,无氧降解速度变化不明显。在苹果汁加工工艺中应尽量隔绝氧气,采用高温(70℃)短时热处理。对成品苹果汁应采用低温贮藏。     

Modeling the combined effects of pH, temperature and ascorbic acid concentration on the heat resistance of Alicyclobacillus acidoterrestis

In this study, thermal inactivation parameters (D- and z-values) of Alicyclobacillus acidoterrestris spores in McIlvaine buffers at different pH, apple juice and apple nectar produced with and without ascorbic acid addition were determined. The effects of pH, temperature and ascorbic acid concentration on D-values of A. acidoterrestris spores were also investigated using response surface methodology. A second order polynomial equation was used to describe the relationship between pH, temperature, ascorbic acid concentration and the D-values of A. acidoterrestris spores. Temperature was the most important factor on D-values, and its effect was three times higher than those of pH. Although the statistically significant, heat resistance of A. acidoterrestris spores was not so influenced from the ascorbic acid within the concentration studied. D-values in apple juice and apple nectars were higher than those in buffers as heating medium at similar pH. The D-values ranged from 11.1 (90 °C) to 0.7 min (100 °C) in apple juice, 14.1 (90 °C) to 1.0 min (100 °C) in apple nectar produced with ascorbic acid addition, and 14.4 (90 °C) to 1.2 min (100 °C) in apple nectar produced without ascorbic acid addition. However, no significant difference in z-values was observed among spores in the juices and buffers at different pH, and it was between 8.2 and 9.2 °C. The results indicated that the spores of A. acidoterrestris may survive in fruit juices and nectars after pasteurization treatment commonly applied in the food industry.     

Examination of bacteriophage as a biocontrol method for salmonella on fresh-cut fruit: a model study

The preparation and distribution of fresh-cut produce is a rapidly developing industry that provides the consumer with convenient and nutritious food. However, fresh-cut fruits and vegetables may represent an increased food safety concern because of the absence or damage of peel and rind, which normally help reduce colonization of uncut produce with pathogenic bacteria. In this study, we found that Salmonella Enteritidis populations can (i) survive on fresh-cut melons and apples stored at 5 degrees C, (ii) increase up to 2 log units on fresh-cut fruits stored at 10 degrees C, and (iii) increase up to 5 log units at 20 degrees C during a storage period of 168 h. In addition, we examined the effect of lytic, Salmonella-specific phages on reducing Salmonella numbers in experimentally contaminated fresh-cut melons and apples stored at various temperatures. We found that the phage mixture reduced Salmonella populations by approximately 3.5 logs on honeydew melon slices stored at 5 and 10 degrees C and by approximately 2.5 logs on slices stored at 20 degrees C, which is greater than the maximal amount achieved using chemical sanitizers. However, the phages did not significantly reduce Salmonella populations on the apple slices at any of the three temperatures. The titer of the phage preparation remained relatively stable on melon slices, whereas on apple slices the titer decreased to nondetectable levels in 48 h at all temperatures tested. Inactivation of phages, possibly by the acidic pH of apple slices (pH 4.2 versus pH 5.8 for melon slices), may have contributed to their inability to reduce Salmonella contamination in the apple slices. Higher phage concentrations and/or the use of low-pH-tolerant phage mutants may be required to increase the efficacy of the phage treatment in reducing Salmonella contamination of fresh-cut produce with a low pH.     

Influence of pH on heat resistance of spores of Bacillus coagulans in buffer and homogenized foods

The influence of pH of heating menstruum (McIlvaine buffer) on the heat resistance of Bacillus coagulans spores has been investigated and compared with the heat resistance in homogenized tomato and asparagus at pH 7 and 4 at a wide range of temperatures. Spores were less heat resistant in all menstrua at acid pH. The magnitude of this effect was greatest at the lowest heating temperatures tested. z values in buffer increased from 8.9 degrees C at pH 7 to 10.5 degrees C at pH 4. pH of menstrua was the main influencing factor, but media composition also influenced heat resistance: at pH 7 heat resistance was similar in all menstrua (D111 degrees C = 1.6 min) but at pH 4 the heat resistance in homogenized foods (D111 degrees C = 0.26 min in tomato and D111 degrees C = 0.28 min in asparagus) was lower than in buffer (D111 degrees C = 0.49 min). The reduced influence of the acidification of media on the heat resistance of B. coagulans at higher temperatures should be taken into account when a rise in the temperature of treatment for canned vegetables is considered to shorten duration of heat processes.     

Thermal inactivation of stationary-phase and acid-adapted Escherichia coli O157:H7, Salmonella, and Listeria monocytogenes in fruit juices

The heat resistance of stationary-phase and acid-adapted Escherichia coli O157:H7, Salmonella enterica (serotypes Typhimurium, Enteritidis, Gaminara, Rubislaw, and Hartford), and Listeria monocytogenes was evaluated in single-strength apple. orange, and white grape juices adjusted to pH 3.9. The heat resistance increased significantly (P < 0.05) after acid adaptation. Salmonella had an overall lower heat resistance than the other pathogens. Acid-adapted E. coli O157:H7 presented the highest heat resistance in all juices at the temperatures tested, with lower z-values than Salmonella and L. monocytogenes. The heat resistance (D(60 degrees C)-values) of all three pathogens, assessed in tryptic soy broth adjusted to different pH values, increased above pH 4.0. From the results obtained in this study, one example of a treatment that will inactivate 5 logs of vegetative pathogens was calculated as 3 s at 71.1 degrees C (z-value of 5.3 degrees C). Normal processing conditions calculated for hot-filled, shelf-stable juices achieve a lethality in excess of 50,000 D for all three pathogens.     

3种天然抗氧化剂对栀子果油氧化稳定性的影响

采用Schaal烘箱法,以过氧化值为指标,研究了3种天然抗氧化剂(维生素E、茶多酚、迷迭香提取物)以及2种增效剂(V_C和柠檬酸)对栀子果油氧化稳定性的影响。结果表明:3种天然抗氧化剂均能不同程度提高栀子果油的氧化稳定性,其中迷迭香提取物的效果最佳;柠檬酸和V_C对迷迭香提取物均表现出良好的抗氧化协同作用,且V_C对迷迭香提取物的协同作用明显优于柠檬酸;添加0.06%迷迭香提取物+0.02%V_C复合抗氧化剂的栀子果油的氧化稳定性明显优于添加0.005%TBHQ的栀子果油。     

Influence of ultra-high pressure homogenisation on antioxidant capacity,polyphenol and vitamin content of clear apple juice

Ultra-high pressure homogenisation (UHPH) is a recently developed technology and is still under study to evaluate its effect on different aspects of its application to food products. The aim of this research work was to evaluate the effect of UHPH treatments on quality characteristics of apple juice such as antioxidant capacity, polyphenol composition, vitamin C and provitamin A contents, in comparison with raw (R) and pasteurised (PA) apple juice. Several UHPH treatments that include combinations of pressure (100, 200 and 300 MPa) and inlet temperatures (4 and 20 °C) were assayed. Apple juice was pasteurised at 90 °C for 4 min. Antioxidant capacity was analysed using the oxygen radical antioxidant capacity (ORAC), 2,2-diphenyl-1-picrylhydrazyl (DPPH), trolox equivalent antioxidant capacity (TEAC), ferric reducing antioxidant power (FRAP) assay while total phenolic content was determined by the Folin–Ciocalteau assay. According to the FRAP and DPPH assays, UHPH processing did not change apple juice antioxidant capacity. However, significant differences were detected between samples analysed by TEAC and ORAC assays. In spite of these differences, high correlation values were found between the four antioxidant capacity assays, and also with total polyphenol content. The analysis and quantification of individual phenols by HPLC/DAD analytical technique reflects that UHPH-treatment prevented degradation of these compounds. Vitamin C concentrations did not change in UHPH treated samples, retaining the same value as in raw juice. However, significant losses were observed for provitamin A content, but lower than in PA samples.