Polyphenol oxidase,total phenolics and ascorbic acid changes during storage of minimally processed ‘California Wonder’ and ‘Quadrato d'Asti’ sweet peppers

A growing sector of ‘minimally processed’ vegetables market is represented by sweet peppers, whose quality may be affected by enzymatic activities. Among these, polyphenol oxidase leads to browning reactions, which is a major cause of quality loss. This research aimed at assessing the changes in PPO activity, total phenolics and ascorbic acid throughout a 30-days cold storage in minimally processed green (cv. ‘California Wonder’), yellow and red (cv. ‘Quadrato d'Asti’) sweet peppers. At day 0 PPO was active in red and yellow fruits but not in green ones, where it started to show relevant activity from the 3rd week of storage. At the end of the storage period (day 30), PPO activity was 1.36, 0.94 and 0.61 U/g d.m. in yellow, red and green peppers, respectively. Total phenols content was highest in green peppers, followed by red and yellow ones. In green fruits it increased up to the 3rd week of storage, decreasing afterwards, whilst in red and yellow fruits phenols content progressively declined after the 2nd week. Yellow fruits showed the highest ascorbic acid content, followed by red and green ones.Results confirm that green peppers ‘California Wonder’ are more suitable to minimal processing than yellow and red fruits.     

MRI ‘texture’ analysis of MR images of apples during ripening and storage

Images obtained by magnetic resonance imaging (MRI) of the apple varieties Idared, Redspur and Topaz during ripening and storage were analysed by texture analysis (TA) to determine the correlation between TA parameters and firmness, soluble solids content (SSC) and titratable acids. All varieties differ significantly in SSC, acidity and the firmness of fruits. Three sagital T2w slices measured at 4.7 T (resolution 256×256 pixels) were analysed numerically using the software MaZda 2.11 and the statistical package S-PLUS 4.5. A significant correlation was found between acidity and TA parameters such as sum average, sum variance and sum entropy. The dynamics of TA parameters during the periods of maturation and storage were described by polynomial functions.The following distinctive TA parameters were found: skewness and kurtosis (among histogram-based parameters), variance of absolute gradient (among gradient-based parameters), grey level nonuniformity (among run length matrix-based parameters) and especially some co-occurrence matrix-derived parameters such as correlation, sum average, sum variance and sum entropy (within 1-, 3-, and 5-pixel neighbourhoods). The TA parameter correlation obtained from MR images can be used for characterising fruit ripening.     

Changes in phytochemical compositions,antioxidant and α-glucosidase inhibitory activities during the processing of tartary buckwheat tea

This study focused on the evaluation of changes in phytochemical compositions, antioxidant and α-glucosidase inhibitory activities during the processing of tartary buckwheat tea. Soak-treating tartary buckwheat significantly decreased the contents of total starch and rutin, whereas significantly increased the contents of quercetin, kaempferol, total flavonoid, and total phenolic compounds. In steam-treating soaked tartary buckwheat for 40–60 min, the contents of total starch, protein, crude fat, isoquercitrin, quercetin, kaempferol, total flavonoid and total phenolic compounds significantly decreased, whereas the content of rutin significantly increased. The reaction of rutin degrading might be catalyzed in soaking processing, and a catalytic reverse shift reaction of rutin-synthesizing might take place in steaming processing. The process of drying and roasting significantly decreased the contents of total starch, rutin, total flavonoid, and total phenolic compounds. The total phenolic content of collected tartary buckwheat materials positively correlated with the antioxidant and α-glucosidase inhibition activities.     

Changes in quality attributes of pulsed light and thermally treated mixed fruit beverages during refrigerated storage (4 °C) condition

The effect of batch pulsed light (PL) irradiation (3000 J cm⁻²) on the shelf-life of the beverage blend comprising apple ber (Indian jujube), carambola (star fruit), and black table grapes was investigated. The equivalent thermally treated beverage (90 °C|5 min) exhibited greater stability from microbial and enzymatic spoilage but retained 27% less antioxidants and 14% less vitamin C than PL-treated juice. Thermally and PL-treated blends possessed sensory scores of 5.8 and 7.2, respectively. The beverage's microbial shelf-life (population ≤ 6-log₁₀ cfu/mL) was extended to 45 days at 4 °C after the PL treatment. The PL exposure did not alter the pH and soluble solids during storage. The PL-treated juice, after 45 days, was placed on par with the freshly prepared juice by the sensory panel. The PL-treated juice preserved 61% more antioxidants, 38.8% more phenolics, and 68.2% more vitamin C than the thermally pasteurized beverage after 45 days of refrigerated storage.Industrial relevanceWhile the fruit processing industry demands microbial safety and enzymatic stability, today's consumer demands juices of high nutritional quality. This study utilizes under-explored fruits like apple ber (Indian jujube) and carambola (star fruit) to make a shelf-stable mixed fruit beverage. This study will help the industry understand the potential of PL treatment in accomplishing microbial safety, enzymatic stability, and nutritional quality, along with the utilization of under-explored fruits.     

Performance of hydroxypropyl methylcellulose (HPMC)-lipid edible coatings with antifungal food additives during cold storage of ‘Clemenules’ mandarins

The performance of edible composite coatings containing hydroxypropyl methylcellulose (HPMC), hydrophobic components (beeswax and shellac), and food preservatives as antifungal ingredients was evaluated on ‘Clemenules’ clementine mandarins. Tested preservatives included potassium sorbate (PS), sodium benzoate (SB), sodium propionate (SP), and their mixtures. Intact fruit or fruit artificially inoculated with Penicillium digitatum or Penicillium italicum, the causal agents of citrus postharvest green (GM) and blue (BM) molds, respectively, were coated and stored up to 30 d at 5 °C plus 7 d at 20 °C of shelf-life. During cold storage, all HPMC-lipid coatings containing food additives significantly reduced the development of both GM and BM, although the performance was better against GM. When coated fruit were transferred to 20 °C, all coatings lost effectiveness. SB + PS-based coating was the most effective to reduce disease severity. All the coatings effectively reduced weight loss and maintained rind firmness of coated ‘Clemenules’ mandarins. The coatings did not adversely affect the ethanol content of the juice, sensory flavor, and fruit appearance. Although the internal gas concentration of coated fruit was modified, the coatings did not induce off-flavor.     

Changes in the bacterial communities of vacuum-packaged pork during chilled storage analyzed by PCR–DGGE

In this study, PCR-denaturing gradient gel electrophoresis (DGGE) was used to investigate the bacterial communities of vacuum-packaged pork during chilled storage. Eight kinds of lactic acid bacteria (LAB) were identified from the strains isolated from MRS plates by PCR–DGGE of the V3 region, and Lactobacillus sakei was the representative isolate at the end of the monitoring. By means of the direct meat analysis of PCR–DGGE, LAB increased gradually and Carnobacterium sp./Car. divergens, Lactobacillus sakei and Lactococcus sp./Lc. piscium, became the predominant bacteria at the end of the storage. The results of Lactobacillus-specific PCR and DGGE showed that different Lactobacillus populations were present at different storage periods and Lb. sakei became the predominant bacteria in the end. In conclusion, the PCR–DGGE technique as a culture-independent method is applicable to monitoring bacterial population dynamics in vacuum-packaged pork.     

Changes in the bacterial communities of vacuum-packaged pork during chilled storage analyzed by PCR–DGGE

In this study, PCR-denaturing gradient gel electrophoresis (DGGE) was used to investigate the bacterial communities of vacuum-packaged pork during chilled storage. Eight kinds of lactic acid bacteria (LAB) were identified from the strains isolated from MRS plates by PCR–DGGE of the V3 region, and Lactobacillus sakei was the representative isolate at the end of the monitoring. By means of the direct meat analysis of PCR–DGGE, LAB increased gradually and Carnobacterium sp./Car. divergens, Lactobacillus sakei and Lactococcus sp./Lc. piscium, became the predominant bacteria at the end of the storage. The results of Lactobacillus-specific PCR and DGGE showed that different Lactobacillus populations were present at different storage periods and Lb. sakei became the predominant bacteria in the end. In conclusion, the PCR–DGGE technique as a culture-independent method is applicable to monitoring bacterial population dynamics in vacuum-packaged pork.     

Quantification of main phenolic compounds in sweet and bitter orange peel using CE–MS/MS

The food and agricultural products processing industries generate substantial quantities of phenolics-rich subproducts, which could be valuable natural sources of polyphenols. In oranges, the peel represents roughly 30% of the fruit mass and the highest concentrations of flavonoids in citrus fruit occur in peel. In this work we have carried out the characterisation and quantification of citrus flavonoids in methanolic extracts of bitter and sweet orange peels using CE–ESI–IT–MS. Naringin (m/z 579.2) and neohesperidin (m/z 609.2) are the major polyphenols in bitter orange peels and narirutin (m/z 579.2) and hesperidin (m/z 609.2) in sweet orange peels. The proposed method allowed the unmistakable identification, using MS/MS experiments, and also the quantification of naringin (5.1 ± 0.4 mg/g), neohesperidin (7.9 ± 0.8 mg/g), narirutin (26.9 ± 2.1 mg/g) and hesperidin (35.2 ± 3.6 mg/g) in bitter and sweet orange peels. CE coupled to MS detection can provides structure-selective information about the analytes. In this work we have developed a CE–ESI–IT–MS method for the analysis and quantification of main phenolic compounds in orange peels.     

Changes in tannin solubility and microstructure of high hydrostatic pressure–treated persimmon cubes during storage at 4 °C

Condensed tannins are important bioactive compounds largely present in persimmon (Diospyros kaki L.f.). The aim of this work was to study the effect of the structural changes occurred during refrigerated storage in persimmon cubes treated with high hydrostatic pressure (HHP) on the solubility and location of tannins, and some physicochemical properties. Persimmon cubes were submitted to 200 MPa for 3 and 6 min at 37 °C and stored at 4 °C for 28 days. The microstructural study was carried out by low-temperature scanning electron microscopy, light microscopy and transmission electron microscopy. The physicochemical properties studied were total soluble tannins (TST), total soluble solids (TSS), pH, lightness, firmness and cohesiveness. Microstructural studies showed that HHP treatment causes cell wall and membrane disruption in persimmon tissue. Retraction of the tonoplast and loss of cell turgor were greater as the storage time increased. Precipitated tannins inside and outside the cells and a progressive separation of adjacent cells during the storage time could be observed. Significant (P < 0.05) decreases in TST, TSS and lightness as well as a significant (P < 0.05) increase in pH took place in HHP-treated samples after 7 days of storage. Samples treated for 3 min showed higher firmness than the rest of the samples during the whole storage period, whereas HHP-treated samples showed higher cohesiveness than the control samples. The effects of HHP treatments and later storage at 4 °C on microstructure, tannin solubility and extractability, and some physicochemical properties of persimmon cubes depend on the treatment conditions and the storage time. HHP treatment might decrease persimmon astringency as well as increase bioactive compounds accessibility.     

Changes in β-carotene bioaccessibility and concentration during processing of carrot puree

The effect of some process and product factors (addition of olive oil, high pressure homogenisation, subsequent thermal or high pressure pasteurisation) on β-carotene bioaccessibility and isomerisation of carrot puree was investigated. High pressure homogenisation could improve β-carotene bioaccessibility by disrupting cells, but only at a pressure higher than 50 MPa. Softening of the cell walls during a subsequent thermal pasteurisation resulted in a further increase in β-carotene bioaccessibility. Unfortunately, the high temperature also induced formation of some undesirable cis-isomers. As cell walls are probably strengthened by high pressure, high pressure pasteurisation could not positively affect the amount of bioaccessible β-carotene. Moreover, the high pressure process induced β-carotene oxidation. A positive effect of olive oil on β-carotene bioaccessibility could only be noticed in combination with a thermal pasteurisation process when β-carotene was solubilised in the oil droplets. Under high pressure however, oil can be crystallised which hinders the solubilisation of β-carotene.     

Changes in physico‐chemical and rheological properties of rice during flaking

Hydration, solubility, pasting and rheological properties of roasted‐parboiled rice and flakes were examined in comparison to raw rice. There was an increase in the hydration capacity, swelling power and solubility during roasting‐parboiling of rice as a result of gelatinization of its starch. Flaking caused further increase due to damage of starch by application of mechanical force. The changes were higher in flakes from roller‐flaker as compared to those from edge‐runner. Pasting characteristics of flour slurries in Rapid Visco Analyzer showed a typical profile for pregelatinized products viz. a higher initial viscosity but a lower peak viscosity for roasted‐parboiled rice and flaked rice than for raw rice. The viscosity curves and flow curves of the products over a wide range of shear rate indicated a non‐Newtonian, pseudoplastic behaviour for all the samples. All samples showed typical hysteresis loop in their viscosity curves indicating their thixotropic nature. Flakes from roller‐flaker exhibited lower viscosity but more thixotrophy indicating higher starch breakdown in them than in edge‐runner flakes, which seemed to have more of heat damaged starch.     

Efficiency of pre-process anoxia treatment on quality of fresh-cut pineapples cv. ‘Phulae’ during storage

The aim of this study was to investigate the competency of pre-process anoxia treatment on physicochemical quality of fresh-cut pineapples cv. ‘Phulae’ during storage. The fruits were kept in anoxia atmosphere (N₂) for 16 h before processing. The fruits were processed immediately after treatment (G1) and after storage at 13 °C for 6 days (G2). Anoxia treatment delayed the weight loss and had no effect on the L* value of both G1 and G2 fresh-cut pineapples. The yellowness (b*) value of G1 fresh-cut pineapple was maintained by anoxia. The PPO activity of anoxia-treated G1 and G2 fresh-cut pineapples was lower than that of untreated fresh-cut fruits (control). Total sugars contents of both G1 and G2 anoxia-treated fresh-cut pineapples trended to be higher than that of control samples. Anoxia had no influence on the total ascorbic acid content during storage. The increases in total bacteria and yeast of both G1 and G2 fresh-cut pineapples were retarded by anoxia. In conclusion, anoxia is a feasible alternative to maintaining quality and delaying microbial increases in fresh-cut pineapples during storage.     

Furosine and Nε-carboxymethyl-lysine in cooked meat product (kavurma): Effects of salt and fat levels during storage

The aim of the study was to determine the effects of different salt (1%, 1.5% and 2%) and fat (10%, 15% and 20%) levels on the content of furosine and N^ε-carboxymethyl-lysine (CML) of kavurma (an uncured-cooked meat product) during the storage time (6 months at 4 °C under vacuum packaging). The increasing salt levels caused an increase in TBARS value. Kavurma with 10% fat showed the lowest mean value for TBARS. The furosine content increased with increasing storage time. At the end of storage, however, furosine content was not affected by the salt level. Kavurma with 20% fat had a higher mean furosine content than 10% fat level at 6th months. The salt level had no significant effect on CML in kavurma, while the interaction of fat level x storage time was significant. After 4 and 6 months of storage, CML content was not affected by the fat level.     

Relationship between the kinetics of β-carotene degradation and formation of norisoprenoids in the storage of dried sweet potato chips

The effects of storage temperature (10; 20; 30; 40 °C), water activity (0.13; 0.30; 0.51; 0.76) and oxygen level (0%; 2.5%; 10%; 21%) on the degradation of carotenoids and formation of volatile compounds during storage of dried sweet potato chips were evaluated. A kinetic model was developed for degradation of trans-β-carotene and it showed that breakdown followed first order kinetics with an activation energy of 64.2 kJ mol⁻¹. The difference between experimental data under laboratory or field conditions fitted and data predicted by the model was less than 10% for trans-β-carotene, or for total carotenoids. The formation of the volatile compounds, β-ionone; 5,6-epoxy-β-ionone; dihydroactinidiolide; β-cyclocitral, was measured by SPME-GC-MS and was clearly related to the degradation of trans-β-carotene. It is also suggested that carotenoid degradation in dried sweet potato was by autoxidation because of the trend in β-carotene degradation rate in relation to water activity or oxygen level.