Changes in texture qualities and pectin characteristics of fermented minced pepper during natural and inoculated fermentation process

Texture qualities and pectin characteristics in fermented minced pepper (FMP) prepared by natural fermentation (NF) and inoculated fermentation (IF) were analysed during fermentation. The results showed variation in texture qualities and pectin characteristics was similar during NF and IF process. The hardness, cell wall material, sodium carbonate-soluble pectin (SSP) and chelate-soluble pectin (CSP) content, and CSP esterification degree decreased, while water-soluble pectin (WSP) content significantly (P < 0.05) increased after fermentation. The rhamnose (Rha) molar ratio in three pectins increased, but arabinose (Ara) and galactose (Gal) molar ratios in most pectins decreased after fermentation. Changes in Ara/Gal and (Gal + Ara)/Rha ratios represented the backbone and branched chains of rhamnogalacturonan-I in three pectins depolymerised during fermentation. The decrease of molecular weight (M_w) in CSP was more obvious than that in WSP and SSP, and it was extensively depolymerised into low-M_w pectin after fermentation. Pearson's correlation analysis showed FMP hardness was extremely (P < 0.01) positively correlated with CSP content and significantly (P < 0.05) positively correlated with SSP content and CSP M_w. Hence, CSP was the main pectin to affect texture compared with WSP and SSP, and its characteristics played a crucial role for regulating FMP texture during NF and IF process.     

Changes in firmness,cell wall composition and cell wall hydrolases of grapes stored in high oxygen atmospheres

To investigate the effects of high oxygen (O₂) atmospheres on the firmness of ‘Kyoho’ grapes (Vitis vinifera L. X V. labrusca L.), changes in cell wall constituents and hydrolase activities were examined during 60 days of controlled atmosphere storage in air (control), 40% O₂ + 30% CO₂ or 80% O₂ (high O₂) at 0 °C and 95% relative humidity. Grapes stored in high O₂ retained greater firmness than grapes stored in air. The cell wall contents of high O₂-stored fruits contained less water-soluble pectin (WSP), more Na₂CO₃ soluble pectin (SSP) and higher hemicelluloses than air-stored fruits. The levels of cellulose and CDTA-soluble pectin (CSP) did not significantly change. The effects of high O₂ on enzyme activity were dramatic for polygalacturonase and β-galactosidase, moderate for cellulase, and very low for pectinesterase. No pectate lyase was detected. Taken together, WSP, SSP and hemicelluloses appeared to have major structural roles in retaining the firmness and preventing the deterioration of fruits kept in high O₂.     

The effect of calcium dips combined with mild heating of whole kiwifruit for fruit slices quality maintenance

The effect of moderate heat treatment combined with calcium dips on the quality of minimally processed kiwifruit was studied. Whole fruits were treated for 25 min at 45 °C by dipping in deionised water or CaCl₂ solutions (1%, 2% and 3% (w/v)) and cooled to 4 °C. Twenty-four hours later fruits were peeled, sanitized, cut into slices and packed. The firmness of kiwifruit slices’ was subsequently evaluated during 8 days of storage. Calcium content, pectinmethylesterase activity and heat shock proteins accumulation were also investigated. Heat treatment conducted in water induced a firming effect and avoid softening of fruit slices while calcium dips had a marginal effect on this parameter. A calcium loss was observed due to dip treatment, but this effect was minimized when treatment was conducted in 3% CaCl₂ solution. The firming effect provided is due to the activation of pectinmethylesterase and the presence of calcium in treatment solution reduces or inhibits enzyme activation. Under the tested conditions, no heat shock proteins de novo synthesis was detected.     

Microstructure changes of sodium carbonate-soluble pectin of peach by AFM during controlled atmosphere storage

Yellow peaches (Prunus persicu L. Batsch.) were stored under controlled atmospheres (CA) of 2% O₂ + 5% CO₂, 5% O₂ + 10% CO₂, 2% O₂ + 10% CO₂, 5% O₂ + 5% CO₂, and normal atmosphere at 2 °C, to investigate the effects of different concentrations of O₂ and CO₂ on the structure of a single sodium carbonate-soluble pectin (SSP) molecule. The microstructure changes, including aggregates and branches, were studied by atomic force microscopy (AFM) at initially, on the 15th and 45th day. The microstructure of SSP molecules and polymers showed that aggregates separated gradually with the storage time. The degradation took place in the linear backbone as well as in side chains. The degradation of SSP molecules was inhibited by lower O₂ and higher CO₂ concentrations. Almost all of the chains were composed of four basic units with widths of 11.719, 15.625, 19.531 and 17.578 nm, which can be visualized and calculated exactly by AFM. This indicated that parallel linkage or intertwist between the basic units was a fundamental characteristic of SSP molecules.     

Using hydrocolloids to decrease oil absorption in banana chips

The aim of this research was to investigate the influence of hydrocolloids (alginate, CMC and pectin) on the oil absorption in fried banana chips. The control banana chips (no hydrocolloid treatment) had oil content as high as 40 g/100 g sample, whereas the sample blanched in 0.5 g CaCl₂/100 ml water and following with immersion in 1 g alginate/100 ml water exhibited a small decrease of oil uptake (p ≤ 0.05) to 38 g/100 g sample. The others which treated with 0.5 g CaCl₂/100 ml and 1 g pectin/100 ml water, and with 0.25 g CaCl₂/100 ml water and 1 g CMC/100 ml water absorbed much less oil (p ≤ 0.05), approximately 23 g/100 g sample. Besides, pectin-treated chips had higher sensory scores in all attributed than CMC-treated sample. These resulted showed that pectin was the most effective hydrocolloid for low fat fried banana chip production. Scanning electron microscope photographs indicted that coating banana chips with pectin was effective in protecting the cellular structure of the banana tissue from damage during deep-fat frying.     

Effect of high pressure/high temperature processing on cell wall pectic substances in relation to firmness of carrot tissue

Thermal processing for food preservation results in undesired softening of fruits and vegetables. To explore the potential of high pressure sterilization in food processing, the effects of combined high pressure/high temperature (HP/HT) treatments on carrot pectic polysaccharides and the related textural properties were investigated and compared with that of samples thermally processed at atmospheric pressure. Disks of fresh carrot (Daucus carota var. Yukon) tissue were subjected to three different treatments (80 °C–0.1 MPa, 100 °C–0.1 MPa and 80 °C–600 MPa) for varying time intervals. Subsequently, the residual texture and microstructural changes of the carrots were evaluated. Alcohol-insoluble residues were prepared from the samples and sequentially fractionated with water, cyclohexane-trans-1,2-diamine tetra-acetic acid (CDTA) and Na₂CO₃ solutions. Thermal treatments at 0.1 MPa caused extensive tissue softening. This was marked by increased cell separation, an increase in water soluble pectin (WSP) paralleled by a decrease in chelator (CSP) and sodium carbonate (NSP) soluble pectin. HP/HT treated carrots showed minimal softening and negligible changes in intercellular adhesion. This was accompanied by a significant reduction in the degree of methyl esterification of pectin, low WSP in contrast to the high CSP and NSP fractions, minor changes in the different pectin fractions during treatment, and a substantial amount of pectin in the fractionation residue. There was a clear difference between HP/HT and thermally processed carrot pectin; HP/HT showing pronounced texture preservation.     

Freezing of strawberries by immersion in CaCl2 solutions

The present investigation studied the freezing of strawberries by immersion in CaCl₂ solutions, analysing drip loss, pectin content and the degree of esterification of the pectins, total and cell-wall bonded calcium contents, the ratio bonded calcium/total calcium, and textural parameters. In addition, the effect of immersion in pectin methylesterase (PME) solutions prior to immersion freezing (IF) was analysed. The firmness of thawed fruit decreased by approximately 74% with respect to fresh strawberries, and neither IF-CA (freezing by immersion in CaCl₂ solution) nor PME–IF-CA (immersion in PME solution + freezing by immersion in CaCl₂ solution) provided significant benefit in maintaining firmness when compared to slow freezing (SF). However, IF provided a significant benefit in reducing drip loss of thawed strawberries when compared to SF, but pre-treatment with PME did not provide any additional benefit.     

Sweetness and texture perception in mixed pectin gels with 30% sugar and a designed rheology

Pure low-methoxyl (LM) pectin and mixtures of LM and high-methoxyl (HM) pectin in different ratios were used to produce gels with control over the rheological parameter storage modulus (G′). The gels either had similar pectin concentrations and different G′ values, or different pectin concentrations and similar G′ values. All gels were prepared with 30 g/100 g sugar, in the presence of 0.1 g/100 g CaCl₂, at pH 3.5; these are conditions that favour gel formation of both LM and HM pectin.The gels were compared for their sensory characteristics; specifically sweetness, sourness, thickness, and glueyness. Sweetness was found to increase with increasing storage modulus (G′) in pectin gels of similar pectin concentration, but different G′ values. Gels with higher proportions of LM pectin were perceived as sweeter than those with low LM pectin ratios. These gels also had increasing loss modulus (G″), and increasing differences between G′ and G″, which indicates that diffusion has a bearing on the perception of sweetness in pectin gels. Thickness and glueyness were mostly determined by total pectin concentration. Thickness also increased with increasing LM pectin concentration while glueyness increased with increasing HM pectin concentration.     

Texture improvement of fermented minced pepper under vacuum impregnation with pectin methylesterase and CaCl2 during fermentation

Fermented minced pepper (FMP) usually suffers from the deterioration of texture quality during fermentation, which can affect sensory and consumer acceptance. In this study, vacuum impregnation (VI) with CaCl₂, pectin methylesterase (PME) and CaCl₂ and PME (PME + CaCl₂ + VI) were compared to improve the texture quality of FMP. FMP treated with PME + CaCl₂ + VI showed the relatively intact cells structure after fermentation. In that case, its firmness maintained high level, while water-soluble pectin (WSP) content was minimum after fermentation. Meanwhile, the molar ratio of most monosaccharides of WSP in PME + CaCl₂ + VI treated FMP decreased, while rhamnose (Rha) molar ratio significantly (p < 0.05) increased after fermentation. The high Rha content represents the stability of rhamnogalacturonan-I linear skeleton of WSP. The negative effect on molecular weight of WSP was delayed by PME + CaCl₂ + VI treatment, and its peak area and value increased after fermentation. Atomic force microscope images indicated that PME + CaCl₂ + VI treatment could retain the long chain and branch structures, and inhibit the degradation of WSP net-like structure at some extent. Hence, PME + CaCl₂ + VI treatment was effective to improve the texture of FMP and inhibit the solubilisation of WSP via the formation of cross-linked pectin chains between Ca²⁺ and demethylesterified pectin.     

Changes in firmness, pectin content and nanostructure of two crisp peach cultivars after storage

To investigate the fundamental of firmness changes of crisp peaches, firmness and pectin contents of two peach (Prunus persica L. Batsch) cultivars (‘Cangfangzaosheng’ and ‘Songsenzaosheng’) stored at 2 °C, 8 °C and 15 °C were investigated. Sodium carbonate-soluble pectin (SSP) extracted showed the highest correlation (positive) with firmness among the three kinds of pectins (water-soluble pectin, chelate-soluble pectin and SSP). The qualitative and quantitative information about SSP nanostructures were determined by atomic force microscopy (AFM). The widths of the peach SSPs were very consistent. The SSP chain widths of both peach cultivars were similar and were composed of several basic units. Schematic models of the changes of the chain widths were proposed. The results indicate that the firmness of peach was closely related with the contents and nanostructural characteristics of SSP, which might be hydrolyzed by enzymes in fruit flesh.     

Study on the efficiency of ethylene scavengers on the maintenance of postharvest quality of tomato fruit

The objectives of this study were to achieve the best level of each ethylene scavenger and evaluate the effect of selected levels of treatments on some quality traits of tomato during storage. Tomato fruits were subjected to four levels of treatments: palladium-promoted nano zeolite, KMnO₄-promoted nano zeolite, 1-MCP, CaCl₂, salicylic acid (SA) and UV-C. The sampling was done at 0, 7th, 14th, 21st, 28th and 35th days of cold storage. The results showed that palladium-promoted nano zeolite 5%, KMnO₄-promoted nano zeolite 20%, 1-MCP 30 ppm, CaCl₂ 2%, SA 1% and UV-C 15 min levels had the most ethylene scavenging function. Effectiveness of the treatments in ethylene scavenging was in the order: palladium?>?KMnO₄?>?1-MCP?>?SA?=?CaCl₂?>?UV-C. The palladium-promoted nano zeolite 5% had more positive effects on phenol content, polygalacturonase activity, lycopene content, fruit firmness and weight loss, and UV-C 15 min had effect on decay severity as compared to the other treatments. Overall, palladium-promoted nano zeolite 5% could be considered not only as favorable tool in tomato shelf life extension but also in preservation of quality characteristics of tomato fruits during storage. Moreover, the UV-C 15 min treatment could be an effective method for reducing decay severity and maintaining postharvest quality of tomato fruits.     

Quality aspects of fresh‐cut ‘long‐storage tomato’ as affected by package,calcium chloride and storage time

In this research, some quality changes during storage at 4 °C were assessed in fresh‐cut fruits of a ‘long‐storage tomato’ landrace, packaged in biocompostable materials (PLA Ingeo tray/NatureFlex? film) or in conventional plastics (PET tray + polypropylene film). The effects of dipping in CaCl₂ on the shelf‐life extension were also assessed. Plants were cultivated both off‐season (greenhouse) and in‐season (open field). CO₂ and O₂ concentration, fruit weight loss, firmness, colour, microbial load were measured at 0, 4, 7, 12 days of storage. Headspace gas changes and fruit weight loss were minimised in conventional package. BIO package prevented water condensation, led to max 5% weight loss and made fruits less susceptible to spoilage. Dipping in CaCl₂ induced better firmness, especially in biopackage. Off‐season fruits had overall lower quality than in‐season fruits; however, these may contribute to extend the production season, with interesting marketing implications for the agri‐food industry.     

PECTIC SUBSTANCES AND FIRMNESS OF CUCUMBER PICKLES AS INFLUENCED BY CACL2, NACL AND BRINE STORAGE1

The effects of brine treatments (CaCl₂ and NaCl) and storage on pectic substances and texture of cucumber pickles were examined. Firmness of cucumber pickles was closely associated with the solubility characteristics and degree of esterification (DE) of pectic substances. Brining, storage, time of CaCl₂ addition and concentration of NaCl and CaCl₂ were all observed to influence the characteristics of pectic substances. Important to preventing softening was maintenance of pectic substances not extractable (NXP) by conventional methods, i.e., by water (WSP), the chelator sodium hex-ametaphosphate (CSP), and dilute alkali (OHSP). Erosion of NXP consistently resulted in increased levels of CSP and reduced firmness. Reducing the amount of demethylation of pectins was also associated with maintaining firmness. Although the DE declined rapidly during brining, tissues from treatments that enhanced firmness had pectic substances with the highest DE. CaCl₂ added to brine at the beginning of fermentation was most effective in preventing the demethylation of pectins and solubilization of NXP. In contrast, delayed addition of CaCl₂ and storage in low NaCl concentration (5% or less) caused greater pectin demethylation, erosion of NXP with concomitant increases in CSP and tissue softening.     

Firmness and Cell Wall Characteristics of Pasteurized Jalapeño Pepper Rings Affected by Calcium Chloride and Acetic Acid

Pepper rings packed in brine containing CaCl₂ were firmer, had higher bound calcium, chelator soluble pectin and pectin DE, and less water-soluble pectin (WSP) than peppers packed in brine containing no CaCl₂. Pepper rings packed in low acid brines (1% and 1.2% acetic acid) were firmer and had less WSP than those packed in high acid brine. Those samples (4% acetic acid) resulted in softening and pectin solubilization, but CaCl₂ resulted in less softening. Monosaccharide composition of cell walls was not affected by CaCl₂ or acetic acid. Firmness retention in CaCl₂ treated samples was probably due to greater association between calcium ions and pectic substances, which resisted acid hydrolysis.     

Can calcium chloride injection facilitate the ageing-derived improvement in the quality of meat from culled dairy cows?

This study investigated whether the positive effects of ageing on tenderness of meat from culled dairy cows can be facilitated by CaCl₂. Injections of 250 mM CaCl₂ solution (10% wt/wt) were performed on Longissimus dorsi samples from 32 7-yrs old cows. Samples were vacuum packaged and aged for 0, 1, 3, 5 and 7 days. Ageing alone produced lighter and less red meat with lower shear force, higher myofibrillar fragmentation and tenderness scores but also elevated lipid oxidation. For most traits investigated, CaCl₂-injected meat exhibited similar ageing effects, but drip loss increased with age. The CaCl₂-injected meat had a lower shear force and myofibrillar fragmentation increased more rapidly, but drip loss, off-flavour scores, colour stability and oxidative stability were inferior to untreated meat. Overall, it was found possible to accelerate tenderisation of such meat with CaCl₂, but only at the cost of adverse effects in some other quality traits.     

Changes in quality attributes throughout storage of strawberry juice processed by high-intensity pulsed electric fields or heat treatments

The effects of high-intensity pulsed electric field (HIPEF) processing (35 kV/cm for 1700 μs applying 4-μs pulses at 100 Hz in bipolar mode) on color, viscosity and PME and PG activities in strawberry juice were studied and compared to those of heat treatments (90 °C for 60 s or 30 s) through 63 days of storage. L^∗ and viscosity values of the HIPEF-processed juices were higher than those found in the thermally treated. In addition, HIPEF-treated juice exhibited lower 5-(hydroxymethyl)-2-furfural (HMF) concentration and browning index than heat-treated juices throughout storage. On the other hand, HIPEF-treated juice maintained low residual pectin methylesterase (PME) activity (13.1%) for 63 days, whereas in the case of the thermally treated, 22.2 and 48.8% was retained after 60 s and 30 s, respectively. Strawberry juice treated by HIPEF achieved lower residual polygalacturonase (PG) activity (73.3%) than those of heat-processed at 90 °C for 60 s (76.2%) or 30 s (96.8%). Thus, HIPEF could be a feasible alternative to thermal processing to minimize browning and viscosity loss in strawberry juice during storage.     

Effect of edible coatings on enzymes,cell-membrane integrity,and cell-wall constituents in relation to brittleness and firmness of Huanghua pears (Pyrus pyrifolia Nakai,cv. Huanghua) during storage

To investigate the effects of edible coatings, such as shellac and Semperfresh™ (sucrose-polyester based coating) on the brittleness and firmness of Huanghua pears (Pyrus pyrifolia Nakai, cv. Huanghua), the changes in the cell-membrane permeability and cell-wall constituents, such as total pectin (TP), Na₂CO₃-soluble pectin (NSP), CDTA-soluble pectin (CSP), water-soluble pectin (WSP), hemicellulose and cellulose were periodically measured, for up to 60 days of cold storage (4 °C) after harvesting. The activities of peroxidase (POD), pectinesterase (PE), polygalacturonase (PG), and cellulose were also assayed. The data suggested that high POD activity and low activity of cell-wall-degrading enzymes, such as PE, PG, and cellulase in the coated pears were associated with a high integrity of the cell membrane and few changes in the cell-wall constituents, which contributed to high levels of brittleness and firmness in the pears during storage; further, the shellac coating provided a better effect than Semperfresh coating.     

Kinetic of the hydrolysis of pectin galacturonic acid chains and quantification by ionic chromatography

These experiments were designed to develop a rapid, repeatable and accurate analysis method for the quantification of galacturonic acid of pectins. Different pectin hydrolysis procedures (chemical and enzymatic) were carried out with H₂SO₄, TFA and HCl at different acid concentrations (0.2, 1 and 2 M) and temperatures (80 and 100 °C). Enzymatic and combined chemical and enzymatic hydrolysis of pectin were also studied. A acid hydrolysis under drastic conditions (100 °C) is insufficient for complete hydrolysis and results in low recovery of galacturonic acid residues. Mild chemical hydrolysis (0.2, 1 and 2 M H₂SO₄ 72 h at 80 °C) is also insufficient for complete depolymerization. Its main advantage is cleavage of the galacturonic acid chains into oligomeric forms without any degradation within 72 h of hydrolysis. However, enzymatic hydrolysis with VL9 for 2 h at 50 °C and combined chemical and enzymatic hydrolysis (0.2 M TFA at 80 °C for 72 h and VL9) give high recovery of this acid. Analysis of the liberated sugar residue by HPAEC allows us to determine the galacturonic acid composition of this polysaccharide accurately with high selectivity and sensitivity in one assay without the need for derivatization.     

In vitro study of the interaction between pectinase and chelate-soluble pectin in postharvest apricot fruits

Firmness is one of the most important quality attributes of apricot fruits and is associated with chelate-soluble pectin (CSP). To elucidate the changes in CSP during postharvest, in vitro investigation of pectinase effects on CSP of apricot fruits was applied to simulate the in vivo changes in CSP fraction during postharvest. It was found that effects of pectinase (40 U/mg) treatment were similar to those of storage time on CSP nanostructures from the results of atomic force microscopy. Relative frequency of widths less than 31.25 nm was 3.6 % for control group, while it was 16.2, 52.0 and 65.5 %, respectively, for 1:10,000 (pectinase/CSP), 1:1,000 and 1:100 pectinase-treated groups. Most of the CSP lengths were 0.5–1 μm, while it was 0–1 μm for pectinase-treated groups. Pectinase treatment had some similar effects on CSP fraction as storage time.