Quality and Antioxidant Properties of Cold-Pressed Oil from Blanched and Microwave-Pretreated Pomegranate Seed

Blanching-Induced Changes in Polyphenol Oxidase, Antioxidants and Phenolic Profile of Mangosteen Pericarp

Research background

Anthocyanin pigments in mangosteen pericarp can serve as natural colourants; however, their stability is compromised by enzymatic browning caused by polyphenol oxidase (PPO). Thus, this study aims to investigate how hot water and steam blanching affect the PPO activity, phenolic profile and antioxidant properties of mangosteen pericarp.

Experimental approach

Fresh mangosteen pericarp was blanched in hot water or steam at 100 °C for 0, 30, 60, 90 and 120 s and the residual PPO activity, total phenolic content (TPC), total anthocyanins, antioxidant activity, browning index and colour properties were evaluated. Additionally, the phenolic compounds were identified using liquid chromatography-mass spectrometry (LC-MS).

Results and conclusions

Zero-order reaction kinetics (R2>0.800) showed that residual PPO activity was significantly (p<0.05) reduced in both blanched and steamed mangosteen pericarp. As expected, PPO was inactivated more rapidly in hot water (t 1/2=59.0 s) than in steam blanching (t 1/2=121.1 s). However, the principal component analysis (PCA) showed that steam blanching for 90 s was the most efficient method, preserving the highest levels of antioxidant capacity, expressed as Trolox equivalents (TE; 9135 µmol/g), Fe(III)-reducing power, expressed as TE, (9729 µmol/g), total anthocyanins (3.03 mg/g), and TPC, expressed as gallic acid equivalents (1057 mg/g). Overall, steam blanching for 90 s was the most efficient method because it best preserved the phenolic compounds and is also a cost-effective method compared to hot water, which needs to be replaced after a few applications.

Novelty and scientific contribution

This is the first study to report the effects of blanching on the anthocyanins mainly present in mangosteen pericarp, in particular cyanidin-3-O-sophoroside (C3S) and cyanidin-3-O-glucoside (C3G), using high-performance liquid chromatography (HPLC) and LC-MS. This study makes a significant scientific contribution to the food industry by providing suitable blanching methods to preserve the quality of bioactive compounds, especially anthocyanins in mangosteen pericarp, which can be used as a natural colourant.

Pomegranate seeds: a comprehensive review of traditional uses, chemical composition, and pharmacological properties

Pomegranate seeds (PS) are the dried seeds derived from pomegranate fruit, accounting for approximately 20% of the fruit's total weight, and are a by-product of pomegranate juice extraction. These seeds hold significance in traditional medicine among Uyghurs and Tibetan cultures, featuring diverse clinical applications within traditional Chinese medicine. These applications include management of gastric coldness and acidity, abdominal distension, liver and gallbladder fever, and pediatric enteritis. PS demonstrates properties such as stomach tonicity, qi regulation, analgesia, and anti-inflammatory effects. Extensive research underscores the richness of PS in various phytochemical compounds and metabolites, notably unsaturated fatty acids (particularly linolenic acid and linoleic acid), phenolic compounds tocopherols, proteins, and volatile oils. Notably, among these bioactive compounds, punicic acid (PA), found within PS, demonstrates potential in the prevention and treatment of cancers, diabetes, obesity, and other ailments. Despite extensive literature on pomegranate as a botanical entity, a comprehensive review focusing specifically on the chemical composition and pharmacological effects of PS remains elusive. Therefore, this review aimed to consolidate knowledge regarding the medicinal properties of PS, summarizing its chemical composition, traditional uses, and pharmacological effects in treating various diseases, thereby laying a foundation for the advancement and application of PS in the field of pharmacology.

Oven-Roasting Effects the Fatty Acid Composition, Antioxidant Properties, and Oxidative Stability of Pomegranate (Punica granatum L.) Seed Oil

In this study, we investigated the effect of roasting conditions and time on the physicochemical properties of pomegranate seed oil. We analyzed the fatty acid, total phenolic, flavonoid, tocopherol, and phytosterol contents of pomegranate seed oil extracted under four conditions: raw, heated at 160°C for 15 min, heated at 160°C for 20 min, and heated at 180°C for 10 min, which included three that were well-established to enhance nutritional and flavor properties. Furthermore, the oxidative stability was evaluated based on the acid value, peroxide value, and induction period. Roasting significantly decreased the contents of punicic acid, polyunsaturated fatty acids, tocopherol, and phytosterol and the 2,2-diphenyl-1-picrylhydrazyl radical scavenging capacity (P<0.05) of the oil. Conversely, saturated fatty acids, monounsaturated fatty acids, acid value, peroxide value, total phenolic and flavonoid contents, and induction period were significantly increased (P<0.05). Our results suggest that the roasting conditions were nutritionally and oxidatively stable, thereby enhancing the roasting process and providing a database for essential roasting treatments for pomegranate seed oil.

Isolation, Characterization and IgE Binding of Two 2S Albumins of Pomegranate Seeds

Literature reports suggest that the presence of proteins in pomegranate seeds is responsible for sensitization and IgE-mediated allergic reactions. The objective of this study was the analysis of a pomegranate seed extract and the isolation and characterization of proteins contained in high amounts. The extract characterization showed a protein profile with main bands at about 18 kDa and below 10 kDa upon SDS-PAGE, and molecules were recognized by specific IgEs upon immunoblotting. Then, two new 2S albumins, a monomeric and a heterodimeric one, were isolated by using classical biochemical methods. They were identified via direct protein sequencing and mass spectrometry, and their primary structure was analyzed and compared with homologous allergenic proteins via bioinformatics. In an Italian population of 703 suspected allergic patients, analyzed by using the FABER® test, the frequency of sensitization to the monomeric and heterodimeric 2S albumins was 1.7% and 0.28%, respectively. This study reports for the first time the isolation and characterization of two 2S albumins from pomegranate seeds. The clinical relevance of these molecules needs further investigation, for instance in populations having different exposures and allergy profiles.

Thermal processing of pomegranate seed oils underscores their antioxidant stability and nutritional value: Comparison of pomegranate seed oil with sesame seed oil

In the present study, the oxidative stability and antioxidant activity of seed oils were investigated in three Iranian pomegranate cultivars, Shirin Khafr, Torsh Sabz, and Rabab, along with the sesame (Sesamum indicume L. cv Dezful) seed oil. Punicic acid was the primary fatty acid in the pomegranate seed oils, with contents ranging from 75.5 to 80.9% (w/w). The tocopherol levels in pomegranate seed oils ranged from 1439 to 2053 mg/kg, whereas the phenolics ranged from 130 to 199.3 mg/kg, respectively. Comparatively, in the seed oil of sesame "Dezful," these substances' contents were 1053 and 79 mg/kg, respectively. Contrary to common perception, the seed oil of the three pomegranate cultivars cultivated in Iran had high oxidative stability and antioxidative activity during the 32 h of thermal processing at 170°C. The oxidation stability assayed by peroxide value, p-anisidine value, and TOTOX index revealed that the pomegranate seed oils had a much higher resistance to the oxidation process than the sesame oil. The content of tocopherols increased during thermal processing due to the regeneration phenomenon. Tocopherols are not always free and may form a matrix with themselves or other compounds. Changes in the antioxidant activity during the thermal processing assessed by DPPH free radical scavenging power and by the FRAP test were consistent with those for the antioxidants. Therefore, these oils can be added to other edible oils as a natural antioxidant to improve their oxidative stability.

Analysis of the Volatile Flavor Compounds of Pomegranate Seeds at Different Processing Temperatures by GC-IMS

This study sought to reveal the mechanism of flavor generation when pomegranate seeds are processed, as well as the contribution of volatile organic components (VOCs) to flavor formation. Gas chromatography–ion mobility spectrometry (GC-IMS), combined with relative odor activity (ROAV) and statistical methods, was used for the analysis. The results showed that 54 compounds were identified from 70 peaks that appeared in the GC-IMS spectrum. Then, the ROAV results showed 17 key volatile components in processing pomegranate seeds, and 7 flavor components with large differential contributions were screened out using statistical methods. These included γ-butyrolactone, (E)-3-penten-2-one (dimer), pentanal, 1-propanethiol, octanal, and ethyl valerate (monomer). It is suggested that lipid oxidation and the Maillard reaction may be the main mechanisms of flavor formation during the processing of pomegranate seeds. Furthermore, this study lays the experimental and theoretical foundations for further research on the development of flavor products from pomegranate seeds.

Evaluation of dry microwave and hot water blanching on physicochemical, textural, functional and organoleptic properties of Indian gooseberry (Phyllanthus emblica)

Indian gooseberry (Phyllanthus emblica) is a seasonal and highly nutritious fruit with shorter shelf-life and astringent taste limiting its utilization. The enzymatic browning and flavor loss are major concerns which makes pre-processing a crucial step for further processing. In this context, dry microwave blanching (MWB) was explored as an alternative to hot-water (HW) blanching to reduce its nutrition losses particularly ascorbic acid (AA) and makes it easier for removal of seed kernel. This study focused on the effect of MW power level (200–500 W) and blanching time (50–100 s) on AA content, color attributes (L*, a*, b*), and enzymatic inhibition in Indian gooseberry. The optimized MWB conditions were 294 W MW power with 70 s blanching time providing satisfactory enzymatic inhibition (75.47%), and retention of AA (417.70 mg/100 g pulp) and color attributes (L*: 58.42, a*: 4.57, b*: 26.23). As compared to HWB (80 °C, 5 min), MWB showed least AA degradation, higher total phenolic content and softening percent with less total color difference owing to its shorter processing time and dry blanching. Quantitative descriptive analysis (QDA) demonstrated that raw and MW blanched Indian gooseberries are the most accepted, followed by HW blanched samples. MWB showed better nutrient retention than HWB with easier seed removal showed the application of MW radiation for blanching of other fruits.

Optimization of Enzyme-Assisted Mechanical Extraction Process of Hodgsonia heteroclita Oilseeds and Physical, Chemical, and Nutritional Properties of the Oils

Hodgsonia heteroclita subsp. Indochinensis W.J.de Wlide & Duyfjes (or Making in Thai) is a neglected and underutilized crop (NUC) with high fat containing nuts. In this study, the enzyme-assisted mechanical extraction of H. heteroclita seed oil was investigated using response surface methodology (RSM) to predict the optimal fat extraction conditions. The most efficient enzyme used in the experiment was a mixture of Flavourzyme^® and Viscozyme^® (1:1, w/w). The predicted maximum oil yield was 46.44%, using the following extraction conditions: 2.98% (w/w) enzyme loading, 48 °C incubation temperature and 76 min of incubation time. H. heteroclita seed oil obtained from heat and enzymatic pretreatments exhibited the highest lightness and viscosity. The chemical properties of this seed oil, including water and volatile compounds (≤0.2% w/w), acid value (≤4.0 mg KOH/g), peroxide value (≤15 mEq of active oxygen/kg) and soap content (≤0.005% w/w), were within the acceptable levels specified by the Codex Alimentarius (2019). H. heteroclita seed oil obtained from heat and enzymatic pretreatments contained the highest content of δ-tocopherol (88.29 mg/100 g) and omega-6 fatty acids (48.19 g/100 g). This study is the first to report on the enzyme-assisted mechanical extraction of H. heteroclita oilseeds as a promising plant material for vegetable oil production.

Effect of some Cultivation Factors and Extraction Methods on Terminalia Catappa L. Seed Oil

Terminalia catappa L. is a common tropic tree for shade and ornament in many countries. Recently, Terminalia catappa L. seed oil has been considered as a new oleaginous seed for dietary and biofuel production. In this study, ripe Terminalia catappa L. fruits originated in Vietnam were collected and seed oil extracted. In our experiment conditions, the effect of tree location, tree age, and annual harvest time on seed weight and seed oil content was investigated. As results, the seeds at the eastern site of the ground obtained not only the biggest size (3.607 g) but also contained the highest oil mass percentage (56.38%). The suitable annual harvesting time for the good seed quality was from March to April. In addition, the Terminalia catappa L. seeds for oil extraction began being harvested in the fourth year with 55.88% oil content compared to 55.99% of the five and six-year-old and trees. After seed drying, the seed oil was extracted by five different methods including cold screw pressing, hot screw pressing, hydraulic pressing, and solvent extracting, and combining method (cold screw pressing then solvent extraction of oil cake). Among the physical methods, cold screw pressing observed the highest oil yield of 77.32%, and the good oil quality was obtained with low free fatty acid (0.550% oleic acid), low acid value (1.080 mg KOH/g oil), and low peroxide value (1.240 meq O2/kg oil). However, the combination of cold screw pressing and cake oil extracting by solvent increased the oil yield by 14.61%. The saponification values fluctuated between 196 to 197 mg KOH/g oil, while the iodine values were in the range of 77.00 and 79.89 g I2/kg oil.

Micro-Encapsulation and Characterization of Anthocyanin-Rich Raspberry Juice Powder for Potential Applications in the Food Industry

Raspberry juice obtained from fresh raspberry fruits was encapsulated separately using gum Arabic (GA), maltodextrin (MT), and waxy starch (WS) (1:10, w/v) and freeze-dried to develop raspberry juice powders (RBJP). The powders were characterised based on their physicochemical and phytochemical composition and their rheological and antioxidative properties, which significantly varied among the carriers. GA- and MT-encapsulated RBJP exhibited a better colour, higher yield, oil holding capacity, total anthocyanin content, and antioxidant properties. WS-encapsulated powder showed a better water holding capacity and total phenolic content; however, the powder was characterised by low solubility, total soluble solids, and redness. Hygroscopicity and titratable acidity did not significantly (p > 0.05) vary among the powders. Cyanidin diglucoside, the main anthocyanin compound identified in the RBJP, was significantly higher in MT (2549.89 µg/g) compared to GA (1935.45 µg/g) and WS (1458.81 µg/g). The RBJP produced using MT and GA showed irregular-shaped and non-spherical particles, which were less agglomerated and relatively larger, while the WS powder exhibited more uniform, spherical particles, which agglomerated together. An X-ray diffraction analysis showed that GA and MT powders had an amorphous structure with minimum crystallinity, while RBJP from WS was crystalline. It can be concluded that GA and MT produced RBJP with quality attributes relevant to the food industry.

Assessing the concentration of conjugated fatty acids within pomegranate seed oil using quantitative nuclear magnetic resonance (qNMR)

INTRODUCTION

Pomegranate seed is rich in oil, and seed oil of pomegranate consists of conjugated fatty acids with different percentages.

OBJECTIVES

The current contribution covers how to determine percentages of different isomeric conjugated fatty acids.

METHODS

The percentages of these isomers are analysed by quantitative nuclear magnetic resonance (qNMR) using benzoic acid as an internal reference chemical with a well-defined amount. Linear mathematical equations are developed for the quantitative analysis of fatty acids found in pomegranate seed oil.

RESULTS

The developed approach is utilised for the pomegranate seed oils prepared in the laboratory and tested for commercial samples. Among the oils derived at the laboratory, the Yeni Hicaz pomegranate cultivar seeds yielded the highest fraction of punicic acid. Among the acids, punicic acid was the one with the highest fraction, while linolenic acid was the one with the lowest percentage.

CONCLUSIONS

These results are important in identifying pomegranate seed oils. Among the commercial samples tested with the current approach, only one of them showed similar content analysis as in the laboratory-derived oils.