EFFECT OF BREAK TEMPERATURE AND HOLDING TIME ON PECTIN AND PECTIC ENZYMES IN TOMATO PULP

SUMMARY –The effect of break temperature and holding time on chemical and physical properties of canned tomato pulp and on the activity of polygalacturonase (PG) and pectin esterase (PE) was investigated. Samples preheated above 200°F were slightly higher in pH value and lower in titratable acidity than those preheated at 160°F and 140°F. The gross viscosity and serum viscosity of the canned tomato pulp increased as break temperature increased. A slight increase in serum viscosity was also observed when holding time was lengthened. The effect of break temperature on serum viscosity was much greater than that of holding time. The total pectin content of the tomato pulp as well as that of the serum increased as the break temperature increased. The same observation holds true for the effect of holding time on the total pectin content of the tomato pulp and tomato serum. This was explained by the inactivation of pectic enzymes at higher break temperature and longer holding periods. The level of PE and PG activity in the frozen tomato pulp decreased as break temperature and holding time increased. No PE activity was detected in samples preheated at 180°F for 15 sec. Samples preheated at 220°F for 15 sec showed no PG activity, while those preheated at 200°F for 15–87 sec still show some PG activity with a retention of about 3.54–5.68%. PG in tomatoes may be inactivated by giving the macerated fruits a hot break temperature higher than 200°F. The critical conditions for inactivation of PE (180°F for 15 sec) and of PG (220°F for 15 sec) found in the course of this investigation are supported by the data obtained on pectin analysis and serum viscosity.     

Calcium and Oxalate Ions Effect on the Texture of Canned Apricots

SUMMARY– Softening of canned apricots was accompanied by increase in soluble pectin and syrup viscosity. Calcium ions have the ability to decrease, to some extent, the movement of pectic material from the fruit to the syrup. This might be explained by the ability of calcium ions to make a bridge between polygalacturonic acid units, thus producing larger molecules which bind the cells together at the middle lamella. Added oxalate ions removed calcium from pectin in the cell wall, causing an increase in water-soluble pectin in the syrup and softening of texture. The mineral contents of canned apricots from three growing areas were determined by flame spectrophotometry. Low potassium in the fruit seems to be related to low pH in the cell sap, causing hydrolysis of pectic materials through hydrolysis ion catalysis and softening during heat processing and storage.     

Application of high hydrostatic pressure and ultrasound-assisted extractions as a novel approach for pectin and polyphenols recovery from tomato peel waste

In this study, high hydrostatic pressure extraction (HHPE) and ultrasound-assisted extraction (UAE) were used for the improvement of pectin and polyphenol recovery from tomato peel waste.HHPE enhanced pectin recovery by 15% after 45 min of recycling, in comparison with the conventional extraction (CE) for 180 min. Similar mass fractions of anhydrouronic acid, total sugars and total phenols were obtained by using both methods. FTIR and ¹H NMR data confirmed that chemical composition of pectin obtained by HHPE and CE is identical, therefore it was concluded that the faster HHPE method can be used for its further isolation.Although depectinized residues subjected to UAE in 70% ethanol for 15 min contained two times lower values of total phenols (1625.7 mg/100 g) than pectinized samples (3643.9 mg/100 g), their quantities are not negligible, considering the fact that they are generated after HHPE. At the end of UAE, the residues were exploited as a source of fatty acids, among which lauric, palmitic and stearic acids are dominant.In conclusion, by shortening the extraction time using HHPE and UAE, it is possible to efficiently produce two valuable functional ingredients, pectin and polyphenols, and at the same time to reduce peel waste from tomato canning industry, which presents an environmental problem.Industrial relevanceUtilizing HHPE and UAE as novel and emerging technologies, and combining them with traditional ones (Soxhlet) is given the solution for sequential isolation of pectin, polyphenols and fatty acids from tomato peel waste, generated by canning factory.Shortening of extraction time using HHPE and UAE, it is possible to replace the conventional techniques, and achieve efficient production of pectin and polyphenols.Overall, the extraction methodology proposed in this work could provide two valuable benefits, i.e. the producers could find mode for decreasing of disposal costs of waste and consumer would take opportunity that isolated compounds could be reintroduced into food.     

Extraction and characterization of pectin from pomelo peel and its impact on nutritional properties of carrot jam during storage

Pectin was extracted using 0.1 N HCl at 90 °C for 120 min at pH 1.5 and 2.0 from pomelo peel and characterized in this study. Influence of various concentrations of extracted pomelo peel pectin on physicochemical, bioactive compounds, color, and sensory attributes of carrot jam during storage was also studied. Pectin extracted at pH 2.0 had higher ash content, equivalent weight, and total anhydrouronic acid content than that extracted at pH 1.0. Extracted pomelo peel pectin was categorized as high‐methoxyl pectin based on the degree of esterification. The β‐carotene and total phenol content were increased in jam after 90 days of storage. Ascorbic acid content decreased with increasing storage period. Jam prepared using commercial pectin had higher ΔE values than jam prepared using pomelo peel pectin. Physico‐chemical properties were influenced by pectin concentrations and storage time. Overall acceptability was similar for all samples on the basis of sensory evaluation. The results showed that pomelo peel might be used as a rich source of pectin and pomelo peel pectin could be used as an alternative to commercial pectins for carrot jam preparation.

Practical applications

Pectin is one of the main ingredients for jam and jelly making. Citrus fruits are main sources of pectin. Usually pomelo peels are discarded as waste materials. However, it could be a good source of pectin. In this article, pectin was extracted from pomelo peel and its application was observed as carrot jam during storage. Therefore, it can be concluded that extraction of pectin from pomelo peel might be used as an alternative to commercial pectin for carrot jam preparation.     

Changes in pectin methylesterification and accumulation of methanol during production of diced tomatoes

The degree of methylesterification (DM) of the pectins in tomatoes affects the firmness of diced products and the consistency of juices. We examined the changes in DM that occur during commercial production of diced tomatoes packed in tomato juice. Ripe processing tomatoes contained low amounts of free methanol (<20 μg g fresh weight⁻¹) and had a high degree of pectin methylesterification (60%). During production of diced tomatoes, the level of free methanol increased while the degree of pectin methylesterification decreased. Diced tomatoes canned in tomato juice contained about 200 μg methanol g fresh weight⁻¹, and had a DM of about 35% in the dice and less than 25% in the juice. Similar results were obtained for aseptically processed bulk packed tomatoes. Low-temperature blanching of canned diced tomatoes caused additional pectin de-esterification in the diced tomatoes and improved firmness. Heating of the diced tomatoes prior to mixing with topping juice, first to temperatures that maximally activate PME then to temperatures that inactivate PME and other enzymes, is proposed as a way to both improve dice firmness and preserve the consistency of the topping juice.     

Structural Characteristics of Pumpkin Pectin Extracted by Microwave Heating

Abstract: To improve extraction yield of pumpkin pectin, microwave heating was adopted in this study. Using hot acid extraction, pumpkin pectin yield decreased from 5.7% to 1.0% as pH increased from pH 1.0 to 2.0. At pH 2.5, no pectin was recovered from pumpkin flesh powder. After a pretreatment at pH 1.0 and 25 °C for 1 h, pumpkin powder was microwave‐extracted at 120 °C for 3 min resulting in 10.5% of pectin yield. However, premicrowave treatment at 60 °C for 20 min did not improve extraction yield. When microwave heating at 80 °C for 10 min was applied after premicrowave treatment, final pectin yield increased to 11.3%. When pH was adjusted to 2.0, the yield dropped to 7.7% under the same extraction conditions. Molecular shape and properties as well as chemical composition of pumpkin pectin were significantly affected depending on extraction methods. Galacturonic acid content (51% to 58%) of pumpkin pectin was lower than that detected in commercial acid‐extracted citrus pectin, while higher content of neutral sugars and acetyl esters existed in pumpkin pectin structure. Molecular weight (M_w) and intrinsic viscosity (η_w) determined for microwave‐extracted pumpkin pectins were substantially lower than acid‐extracted pectin, whereas polydispersity was greater. However, microwave‐extracted pectin at pH 2.0 had more than 5 times greater M_w than did the pectin extracted at pH 1.0. The η_w of microwave‐extracted pectin produced at pH 2.0 was almost twice that of other microwave‐extracted pectins, which were comparable to that of acid‐extracted pectin. These results indicate that extraction yield of pumpkin pectin would be improved by microwave extraction and different pectin structure and properties can be obtained compared to acid extraction. Practical Application: Pumpkin is a promising alternative source for pectin material. Pumpkin pectin has a unique chemical structure and physical properties, presumably providing different functional properties compared to conventional commercial pectin sources. Depending on the conditions to produce pumpkin pectin, diverse molecular structures can be obtained and utilized in various food applications.     

Analyses of tomato peel and seed byproducts and their use as a source of carotenoids

Commercial tomato canning yields two different byproducts. One is the material that results from peeling tomatoes, while the other results from removing the seeds. The peel byproduct contained 100.8 g protein, 256.4 g ash and 299.4 g acid detergent fiber kg^?1. Ash content was high because the peel byproduct contained 83.8 g kg^?1 sodium as a result of using a sodium hydroxide solution to peel the tomatoes. The seed byproduct contained 202.3 g protein, 51.8 g ash, and 537.9 g acid detergent fiber kg^?1. An amino acid analysis of seeds indicated that approximately 60% of the protein results from amino acids. Both byproducts were analyzed for carotenoid content. The lycopene content of peel byproduct was 734 µg g^?1 of dry material. Significant amounts of lutein, β‐carotene, and cis‐β‐carotene were also present. Seed byproduct contained 130 µg lycopene kg^?1 of dry matter. The content of other carotenoids was approximately half of that present in the peels. Peel and seed byproducts were included at 75 g kg^?1 in hen diets to determine the transfer of carotenoids to the yolk. When fed at this concentration, the lycopene content of dry egg yolk was approximately 0.9 µg g^?1. Approximately 0.1% of the lycopene in peel byproduct and approximately 0.7% of the lycopene in the seed byproduct was transferred from the feed to the yolk. Lycopene appears more similar to carotene than to oxycarotenoids in its transfer to the yolk. Copyright © 2005 Society of Chemical Industry     

Structural Collapse and Volatile Retention During Heating and Rehumidification of Freeze-Dried Tomato Juice

The effects of temperature, moisture content, and pectin addition on the “collapse” of freeze-dried tomato juice cake and retention of volatiles were investigated. High temperatures and high moisture contents induce collapse and the loss of volatiles, which was measured with ¹⁴C-labelled butyl acetate. The addition of pectin, which enhances the viscosity of the tomato juice, increases its “collapse” temperature after freeze-drying and the retention of volatiles.     

Physiochemical Properties,Microstructure, and Probiotic Survivability of Nonfat Goats’ Milk Yogurt Using Heat‐Treated Whey Protein Concentrate as Fat Replacer

There is a market demand for nonfat fermented goats’ milk products. A nonfat goats’ milk yogurt containing probiotics (Lactobacillus acidophilus, and Bifidobacterium spp.) was developed using heat‐treated whey protein concentrate (HWPC) as a fat replacer and pectin as a thickening agent. Yogurts containing untreated whey protein concentrate (WPC) and pectin, and the one with only pectin were also prepared. Skim cows’ milk yogurt with pectin was also made as a control. The yogurts were analyzed for chemical composition, water holding capacity (syneresis), microstructure, changes in pH and viscosity, mold, yeast and coliform counts, and probiotic survivability during storage at 4 °C for 10 wk. The results showed that the nonfat goats’ milk yogurt made with 1.2% HWPC (WPC solution heated at 85 °C for 30 min at pH 8.5) and 0.35% pectin had significantly higher viscosity (P < 0.01) than any of the other yogurts and lower syneresis than the goats’ yogurt with only pectin (P < 0.01). Viscosity and pH of all the yogurt samples did not change much throughout storage. Bifidobacterium spp. remained stable and was above 10⁶CFU g^‐1 during the 10‐wk storage. However, the population of Lactobacillus acidophilus dropped to below 10⁶CFU g^‐1 after 2 wk of storage. Microstructure analysis of the nonfat goats’ milk yogurt by scanning electron microscopy revealed that HWPC interacted with casein micelles to form a relatively compact network in the yogurt gel. The results indicated that HWPC could be used as a fat replacer for improving the consistency of nonfat goats’ milk yogurt and other similar products.     

FREEZE PEELING IMPROVES QUALITY OF TOMATOES

SUMMARY— A process of peeling tomatoes using low temperature-short time freezing was perfected. Liquid nitrogen (BP-196°C was used as the refrigerant for freezing the skin and only a thin layer of cells just beneath the skin. The fruit was immediately thawed, after which the skin was quickly and easily removed from the fruit. Liquid nitrogen-peeled samples were evaluated for loss of peel and trim, as well as lycopene and carotene in the peeling process and these losses compared with samples peeled in boiling water. The losses in peel and trim were reduced by approximately 50%, and significantly less lycopene was lost by nitrogen peeling. The peel and trim of fall tomatoes had a greater amount of lycopene and carotene than spring tomatoes. The nitrogen-peeled samples were canned without additives, with sodium chloride and with calcium chloride added and compared with samples peeled with boiling water. There was a decrease in the percentage of broken fruit in the canned tomatoes peeled by liquid nitrogen. Titratable acidity and °Brix were higher and pH was lower in these samples. Color of the homogenized canned product was not statistically different; however, the nitrogen-peeled tomatoes had a better visual color. The calcium chloride added-nitrogen-peeled samples possessed a higher degree of firmness than the comparably treated boiling-water-peeled samples, indicating that the nitrogen-peeled tomatoes utilized the added calcium to a greater extent in firming.     

Role of pectic polysaccharides in structural integrity of apple cell wall material

Texture modulating properties of aqueous dispersions of apple cell wall material differed from those of tomato or kiwifruit, particularly under high shear. It was previously hypothesized that this may be due to the fact that the apple cell wall showed less in vivo solubilization of pectic polysaccharides during ripening compared to tomato or kiwifruit. However, in vitro solubilization of the pectic polysaccharide content of apple CWM by endo-polygalacturonase and/or extraction with 0.05 M sodium carbonate, did not affect the loss in wall integrity shown by tomato or kiwifruit CWMs under shear. In addition, the pectin-depleted residue after Na₂CO₃ extraction possessed better water retaining and viscosity generating properties than the original cell wall material. Following treatment of apple CWM with cellulase, the viscosity of suspensions decreased, emphasising the role that the cellulose–hemicellulose network plays in the water-retaining capacity of the cell wall. Residue from CWM after cellulase treatment consisted of ∼85% pectic polysaccharides. Surprisingly, the integrity of these “cellulose-free” walls was maintained after shear. It is concluded that differences in structural properties of the CWMs of apple compared to kiwifruit or tomato are not simply related to pectin solubilization but to a fundamental difference in the architecture of the apple cell wall.     

Effect of Fertilization, Postharvest Handling and Blanching Temperature on the Drained Weight of Canned Summer Squash

There was no apparent effect on drained weight or firmness when three rates of calcium fertilization and two rates of potassium fertilization were applied to a test planting from which two harvests of raw summer squash were canned. However, high Ca (L₂) decreased dry matter and increased structural carbohydrates and tissue Ca in the canned product. Precooling increased drained weight and dry matter, but drastically reduced firmness of the canned product. Noncooled canned squash had lower drained weights and pH, but greater firmness and higher water soluble pectin and cellulose content. Blanching at 99°C increased drained weight; blanching at 88°C decreased drained weight, but increased calgonsoluble pectin content.     

Evaluation of Lye and Steam Peeling Using Four Processing Tomato Cultivars

Fruit of four eastern tomato cultivars (cvs) were peeled using either high pressure steam or a lye bath under commercial conditions. Percent yield of whole fruit and finished product quality were determined. Yield of 5 sec steam-peeled fruit was 4.1% greater than lye-peeled fruit; no cvs differences were detected. Quantity of blossom-end peel was not affected by peel treatment, but differences among cvs were shown. Steam-peeled tomatoes averaged 6.2 cm² and lye-peeled < 1 cm² total peel/can. There were no differences among treatments or cvs in sensory color scores. Differences in surface bL/a values among cvs at the equator region of fruit were found. Although recovery was greater for steam-peeled than for lye-peeled fruit, canned product quality was better for lye-peeled fruit.     

柚皮果胶的提取方法比较及其粘流性能研究

比较了从江永柚皮中提取果胶的不同方法。研究了柚皮果胶溶液的粘流性能,测定了果胶的特性粘度并由此计算出果胶的分子量。结果表明:盐酸逆流萃取法为从柚皮中提取果胶的较好方法,果胶溶液的粘流活化能约为17.14kJ/mol(依赖于果胶浓度大小),采用逆流萃取法提取的果胶特性粘度为4.492ml/g,果胶分子量为7.17×104。     

Characterization of polyphenol oxidase from Uapaca kirkiana fruit

Polyphenol oxidase (PPO), the enzyme responsible for the postharvest spoilage of fruits, was extracted and purified from Uapaca kirkiana peel and pulp by ammonium sulfate precipitation and dialysis. Further purification of peel PPO was carried out by gel filtration chromatography. Optimum pH values were 7 and 8 for peel and pulp PPO, respectively. The optimum temperatures for peel and pulp PPO were 45 and 35 °C, respectively. Inhibition studies of the PPO enzyme were performed using citric acid, sodium azide, sodium metabisulfite and thiourea. The most effective inhibitors were sodium azide and citric acid for both peel and pulp PPO. V_max and K_m values were 13.63 units min^?1 and 4.923 mmol L^?1, respectively, for peel PPO and 14.03 units min^?1 and 5.43 mmol L^?1, respectively, for pulp PPO. Three isoenzymes of Uapaca kirkiana PPO were detected by polyacrylamide gel electrophoresis. One of the isoenzymes could be identified as having a molecular weight of 26 625 Da. Copyright © 2005 Society of Chemical Industry     

干装苹果罐头减压预抽辅助碱性钙处理工艺优化

为控制干装苹果罐头果肉组织软化,以秦冠苹果为原料,通过单因素试验考察Ca2＋质量浓度、预抽真空度和预抽液pH值对不同钙形态（水溶性钙、氯化钠溶性钙、醋酸溶性钙、盐酸溶性钙）含量、细胞壁组分（水溶性果胶、螯合剂溶性果胶、碳酸钠溶性果胶、半纤维素）含量的影响。在此基础上,采用Box-Behnken试验设计方法和Design-Expert 8.0数据分析软件,以氯化钠溶性钙含量和螯合剂溶性果胶含量为响应值优化干装苹果罐头减压预抽辅助碱性钙处理工艺。结果表明,氯化钠溶性钙含量和螯合剂溶性果胶含量在干装苹果罐头果肉组织中的含量最高,且各因素对二者的影响显著;当Ca2＋质量浓度2.0 g/L、预抽真空度0.08 MPa、预抽液pH 2.8时,干装苹果罐头氯化钠溶性钙含量为55.26 mg/kg,螯合剂溶性果胶含量为17.45 mg/g,与预测值的相对误差较小。该研究为调控干装苹果罐头果肉组织软化和指导生产实践提供部分理论依据。     

Husk Tomato (Physalis ixocarpa Brot.) Waste as a Promising Source of Pectin: Extraction and Physicochemical Characterization

Husk tomato (Physalis ixocarpa Brot. var. Rendidora) waste was evaluated as a source of specialized pectin, and pectin extracted from this waste was characterized physicochemically. Fruit was blanched for 10 or 15 min and extracted in 0.1 N HCl for 15 to 25 min. Extracted pectin was subjected to physicochemical analysis. For all extraction conditions, the percentage of anhydrogalacturonic acid exceeded 60%, indicating that husk tomato was a good source of pectin. The degree of esterification of pectin molecules was 63% to 91%. The amount of extracted pectin decreased with increasing extraction time. The apparent viscosity of husk tomato pectin showed the characteristic behavior of pseudoplastic fluids. Neutral sugars were identified, and the amounts of 6 sugars (fucose, rhamnose, arabinose, galactose, glucose, and xylose) were quantified. Sugars identified in husk tomato pectin and present in the Rhamnogalacturonan I region, arabinose, galactose, and rhamnose suggest a highly branched structure, which will influence its future applications. Molecular weight values were 542 to 699 kDa, exceeding molecular weight values reported for commercial citrus pectins from 134 to 480 kDa. The extraction process significantly (P < 0.05) influenced the physicochemical properties of pectin. Up to 19.8% from the total amount of pectin in the husk tomato was extracted by 10 min of blanching and 20 min of a more heat treatment. Our findings indicate that husk tomato can be a good alternative source of pectin having highly distinctive physicochemical characteristics.     

Study of the suitability of HRMAS NMR for metabolic profiling of tomatoes: Application to tissue differentiation and fruit ripening

The feasibility of HRMAS NMR as an efficient technique for metabolic studies of tomato fruit and tomato tissues is described. A good-taste tomato variety from Almería (Spain) (commercial name Zayno) was chosen for this study. Fruits of three different ripening stages (green, turning and red) were selected, based on their external appearance. NMR data of whole fruits were obtained through ¹H HRMAS NMR spectra of tomato purée. Flesh, peel and seeds from mature red fruits were separately analysed. ¹H HRMAS NMR spectra showed resolutions similar to that of solution ¹H NMR with the advantages of minimal sample manipulation and possibility of analysing polar and non-polar compounds simultaneously. Seeds could be clearly distinguished by visual comparison of the spectra. Tryacylglycerols, in which linoleic (47%) and oleic (28%) acyl chains preponderate, were the major components of seeds. By contrast, signals of fructose, glucose, citric acid, and the amino acids GABA, glutamine and glutamate dominated the spectra of flesh, peel and tomato purée. Principal components analysis, performed on the covariance matrix, revealed a clear separation between peel and flesh. Apart form the presence of the cutin biopolymer, peel showed a specific accumulation of sugar and sugar moieties related to pectin degradation, as well as glycosylated metabolites. Chemometric analysis also allowed the metabolic trajectory from green to red mature stages to be visualised. However, sample heterogeneity in the analysis of the whole fruit proved to be an important issue. The source of such heterogeneity was assigned to the presence of tissues of different hardness in the small amount of sample used. The presence of two clusters of samples at the turning stage indicated that the levels of certain metabolites could diverge significantly in fruits with almost identical appearance.     

微切变-助剂互作技术辅助提取柑橘皮果胶的工艺研究

目的建立并优化微切变-助剂互作技术提取橘皮果胶的工艺方法。方法采用固态氯化钠为助剂,雪峰蜜橘为主要原料,以果胶的提取率为评价指标,采用单因素和正交实验探索果胶的最优提取工艺,包括Na Cl助剂量、浸提时间、料液比、提取液pH 4个单因素。结果最优工艺条件为:助剂添加量2.5%(m:m)、浸提时间80 min、料液比1:20(m:V,g:mL)、提取液pH为2,此条件下果胶提取率为23.16%,比对照组提高了48.18%,且提取总时长由242 min缩短到102 min。结论以氯化钠为助剂的微切变-助剂互作技术高效省时、安全可靠,为柑橘副产物的高附加值综合利用提供了理论参考。     

Improvement of Flavor and Viscosity in Hot and Cold Break Tomato Juice and Sauce by Peel Removal

Tomatoes are typically not peeled before being made into juice but the peels contain enzymes that affect the odor, flavor, and viscosity of the juice. The peels are removed in the finisher, but their presence during the break process may affect quality. Juice was processed from peeled and unpeeled tomatoes using hot or cold break. The juices were pasteurized by high temperature short time (HTST), low temperature long time (LTLT), or with a retort. The control samples were treated with 10% calcium chloride to stop enzymatic activity in the juice. Sauce was made from juice and the tomato products were analyzed for volatiles, color, viscosity, and by sensory. Cold break juice made with peel contained higher levels of some lipoxygenase‐, carotenoid‐, and amino acid–derived volatiles, than the juice made without peel. Because of the lack of enzyme activity, hot break juices had lower levels of these volatiles and there was no significant difference between hot break juices made with and without peel. CaCl₂‐treated and HTST juice had higher levels of most of the volatiles than LTLT, including the lipoxygenase‐derived volatiles. The presence of peel produced a significant decrease in the viscosity of the cold break juice and sauce. There was no significant difference in the hue angle, total soluble solids, pH, titratable acidity, and vitamin C for most of the treatments. The texture, flavor, and overall liking of cold break juice made without peel were preferred over cold break juice made with peel whereas the color was less preferred. Between the sauces no significant differences in preference were obtained.