Improving quality of cumin powder through cryogenic grinding technology

Cumin (Cuminum cyminum L.) seeds contain numerous phytochemicals. A study was conducted to evaluate the effect of cryogenic grinding over traditional grinding method of cumin seeds so as to determine the optimum grinding condition for high quality cumin powder. Effect of cryogenic grinding at varying temperatures (?30 to 10 °C and ambient), feed rates (5 to 7 kg/hr), and sieve size (0.8 to 1.5 mm) were evaluated with respect to mean particle size, grinding time, and volatile oil content. It was found that cryogenic grinding retained 62.56% more volatile oil as compared to ambient grinding. On the basis of retention of volatile oil, the premium quality cumin powder was obtained at grinding temperature ?30 °C with a feed rate of 7 kg/hr and sieve size of 0.8 mm. The storage study of cryo‐ground cumin powder confirmed that refrigerated storage had advantage over ambient storage in terms of freshness and volatile oil for longer periods. Cryo‐ground cumin powder retained 3.3% volatile oil which contained 29.61% cuminaldehyde and 5.36% γ‐terpinene along with other compounds.

Practical applications

• Cryo‐ground cumin powder retained more volatile oil which improves the quality of ground cumin powder.
• Cryo‐ground cumin powder has higher market value thus, more profit to processors and high quality product to consumer.
• The study revealed the importance of cryogenic grinding of valuable spices to retain its freshness and organoleptic qualities.

     

Volatile compounds and changes in flavour‐related enzymes during cold storage of high‐intensity pulsed electric field‐ and heat‐processed tomato juices

BACKGROUND: The effects of high‐intensity pulsed electric field (HIPEF) processing (35 kV cm^?1 for 1500 µs, using 4 µs bipolar pulses at 100 Hz) on the production of volatile compounds and flavour‐related enzymes in tomato juice were investigated and compared with those of thermal processing (90 °C for 30 or 60 s). RESULTS: Tomato juice treated by HIPEF showed lower residual lipoxygenase (LOX) activity (70.2%) than juice heated at 90 °C for 60 s (80.1%) or 30 s (93.2%). In contrast, hydroperoxide lyase (HPL) was almost completely inactivated when the juice was subjected to 90 °C for 60 s, whereas roughly 50% of the control tomato juice was depleted after HIPEF treatment or thermal processing at 90 °C for 30 s. A slight decrease was observed in the initial LOX activity of treated and untreated samples during storage, whereas initial HPL activity was strongly affected over time. CONCLUSION: HIPEF‐treated juice exhibited higher levels of compounds contributing to tomato aroma than untreated and heat‐treated juices throughout storage. Thus HIPEF processing can preserve flavour quality and stability of tomato juice compared with conventional thermal treatments. Copyright © 2010 Society of Chemical Industry     

Lipid stability in powdered infant formula stored at ambient temperatures

Lipid stability of standard infant formula was evaluated at ambient temperatures, namely 25, 30 and 37 °C, during 3 months. Lipids were thoroughly analysed to evaluate changes in fatty acid composition and trans fatty acid isomers, non‐volatile oxidation compounds including oxidised, dimeric and polymeric triacylglycerols, and tocopherol. No significant changes in either of the parameters examined were found in total lipids extracted from infant formula along the storage period. However, the minor free oil fractions (about 7.5% of total lipids) showed a significant increase in oxidation compounds and marked decrease in tocopherol levels during storage at all temperatures. Samples stored at 37 °C for 3 months were rancid and, accordingly, contained the highest oxidation level in the free oil fraction, whereas total lipids extracted were apparently not oxidised. Results showed the necessity of analysing separately the free oil fraction in infant formulae to obtain a clear picture of the oxidation status.     

Volatile compounds of black cumin seeds (Nigella sativa L.) from microwave-heating and conventional roasting

The volatile compounds in raw, conventionally roasted and microwave roasted black cumin (Nigella sativa L.) seeds at 0.45 kW for 2, 4, and 8 min, were analyzed by headspace-SPME gas chromatography-mass spectrometry. Among the 38 volatile compounds identified, the major compounds were thymoquinone and p-cymene in all samples. The levels of these compounds decreased with roasting. However, concentrations of pyrazines and furans increased significantly as a result of roasting and these compounds may affect the flavor of roasted black cumin seeds. Methyl pyrazine and 2,5-dimethylpyrazine were major pyrazines, formed at high concentration in seeds roasted for 8 min and in conventional roasting.     

Nanoencapsulation of black seed oil by coaxial electrospraying: characterisation,oxidative stability and in vitro gastrointestinal digestion

In this study, black seed oil-loaded zein nanoparticles were produced via coaxial electrospraying. Nanoparticles obtained under optimised conditions had a uniform morphology with a mean diameter of 136 nm and a core–shell structure verified by confocal laser scanning microscope. The encapsulation efficiency of the oil in nanoparticles ranged from 65.3 to 97.2%. The peroxide value of oil in nanoparticles with high encapsulation efficiency was approximately three times lower than unencapsulated oil when stored at 60 °C for 55 days. The totox value of the encapsulated oil in nanoparticles stored at 25 °C was lower than the critical totox value of 30. The amount of thymoquinone released from encapsulated oil was low at the end of the gastric digestion, but the bioaccessibility of thymoquinone from encapsulated oil increased during intestinal digestion compared with free oil. These results demonstrated the successful nanoencapsulation of black seed oil with the improved oxidative stability due to the coaxial structures formed. Black seed oil-loaded zein particles may have the potential to expand the use of black seed oil as a functional ingredient for food systems.     

Changes in antioxidant concentration of virgin olive oil during thermal oxidation

The concentration of α-tocopherol, hydroxytyrosol derivatives and tyrosol derivatives was measured in samples of virgin olive oil during thermal oxidation at 60 and 100 °C. Hydroxytyrosol derivatives are the first antioxidants that are lost during thermal oxidation (until a peroxide value of 20–30 meq/kg). Tyrosol derivatives seem to be the most stable compounds, while α-tocopherol has an intermediate rate of loss at low peroxide values and is destroyed at peroxide values from 20 to 50 meq/kg. This means that hydroxytyrosol derivatives are the first compounds to be oxidized, providing therefore oxidative stability to the oil. α-Tocopherol seems to be oxidized after a significant decrease on hydroxytyrosol derivatives content. Tyrosol derivatives are the antioxidants that decrease with the lowest rate, providing the oil with the less antioxidant activity.     

Fatty acid profile, thymoquinone content, oxidative stability, and antioxidant properties of cold-pressed black cumin seed oils

Six different batches of cold-pressed black cumin seed oils (BCSO) were evaluated for their fatty acid profiles, thymoquinone contents, oxidative stability, and antioxidant properties. Linoleic, oleic, and palmitic acids were the major fatty acids in the tested oils. The cold-pressed BCSO samples differed in their oxidative stability measured as the oxidative stability index (OSI). The greatest OSI was about 155 h, and the lowest OSI was proximately 76 h, reflecting a 2-fold difference in their oxidative stability. These BCSO contained significant level of phenolic components with a concentration ranging from 1.02 to 1.40 mg gallic acid equivalents/g oil. In addition, BCSO contained about 3.48-8.73 mg/g thymoquinone and trace amount of dithymoquinone. Electron spin resonance (ESR) analysis showed that cold-pressed BCSO contained natural antioxidants and was able to suppress radical mediated lipid peroxidation in fish oil. The methanol extracts of BCSO could directly react with and quench DPPH radicals, which further confirmed the antioxidant property of these BCSO. The results from the present study suggest that cold-pressed black cumin seed oil may serve as an excellent dietary source of thymoquinone and natural antioxidants.     

Effect of black tea, garlic and onion on corn oil stability and fatty acid composition under accelerated oxidation

Fresh black tea, garlic bulbs and onion skin were macerated in refined corn oil to evaluate their antioxidant properties and the effect of heat on oil stability and fatty acid composition in accelerated oxidation experiments at 55 ° and 140 °C. At the lowest temperature control and onion treatments showed an induction time of 3 days with maximum peroxide values of 62 and 45 meq kg^?1, respectively. Addition of black tea and garlic increased oil stability with peroxide values of 5 meq kg^?1, without appreciable changes in the fatty acid composition. Heating at 140 °C for 48 h produced an accelerated deterioration of corn oil in all treatments. A reduction of polyunsaturated fatty acids of about 40% was observed, with high concentrations of non‐eluted materials which contained thermo‐oxidized substances. It was found that natural extract of black tea and garlic were effective to preserve corn oil under accelerated oxidation at 55 °C which simulates oil behaviour during storage, but cannot reduce the rate of oxidation at frying temperatures.     

Effect of plant extracts on the oxidative stability of sunflower oil and emulsion

The antioxidative activities of six plant extracts (catnip, hyssop, lemon balm, oregano, sage and thyme) were evaluated in sunflower oil and its 20% oil-in-water emulsion in the dark at 60°C. The oxidation process was followed by measuring the formation of primary (conjugated diene hydroperoxides) and secondary (volatile compounds) oxidation products. Sage extracts (600 and 1200 ppm) effectively inhibited the formation of conjugated dienes and volatile compounds (hexanal and pentanal) in oil and emulsion and showed the highest antioxidative activity compared with 300 ppm BHT. Thyme and lemon balm extracts inhibited hexanal generation more than formation of conjugated dienes in both oil and emulsion. Oregano extract was more active in oil than in emulsion. Catnip and hyssop extracts (600 ppm) showed prooxidative action to sunflower oil at 60°C. These two extracts increased the formation of conjugated dienes compared with the control oil. In emulsions, catnip extract (600 ppm) was active and significantly inhibited the formation of conjugated dienes more than BHT (300 ppm) during additional incubation.     

Effect of combined application of plant extract and vacuum packaged treatment on the quality of hot smoked rainbow trout

The effect of plant extract (bay leaf, rosemary, black cumin seed and lemon oil) treatment on the shelf life of vacuum-packaged fish was studied. Hot smoked rainbow trout was treated with 1 % plant extracts, and their shelf lives were compared with those of control (only vacuum packaged) samples. Samples were stored at 2 °C and sensory evaluation as well as chemical and microbiological analyses were conducted weekly. The control group was spoiled after four weeks of storage. In contrast the addition of plant extracts decreased microbiological activity. The results obtained from this study showed that the shelf life of hot smoked trout stored in cold storage (+2 °C), as determined by overall acceptability of all data, was 6 weeks for rosemary, black cumin seed, and lemon oil treatment plus vacuum packaged fish and 7 weeks for bay leaf oil treatment plus vacuum packaged smoked fish.     

Antioxidant activity and phenolic content of phenolic rich fractions obtained from black cumin (Nigella sativa) seedcake

The antioxidant activities of crude methanolic extract (CME) and its fractions using ethyl acetate (EAF), hexane (HF) and water (WF) of black cumin seedcake were investigated. DPPH radical scavenging activity, β-carotene–linoleate bleaching, and inhibition of corn oil oxidation were used to evaluate the antioxidant capacity. The total phenolics were found to be 78.8, 27.8, 32.1 and 12.1 mg gallic acid equivalents (GAE)/g in EAF, CME, WF and HF, respectively. The CME and EAF exhibited the highest DPPH followed by WF and HF. The extract/fractions showed high effect on reducing the oxidation of β-carotene. The effect of extract/fractions on the oxidative stability of corn oil at 70 °C was tested in the dark and compared with butylated hydroxyanisole (BHA). The oil peroxide and anisidine values were generally lower with addition of PRFs in comparison to a control. The predominant phenolic compounds identified by HPLC–DAD in CME and WF of black cumin seedcake were hydroxybenzoic, syringic and p-cumaric acids.     

Effects of storage conditions on oxidative stability of soybean oil

Soybean oil in the presence or absence of 200 µg g^?1 tert‐butyl hydroquinone (TBHQ) was subjected to accelerated oxidative storage at 60 °C for 10 days or stored at room temperature for 12 months. Tocopherol contents of the oil decreased, whereas the headspace volatiles and peroxide values (PV) increased as the storage time increased. During accelerated storage, TBHQ was effective in retarding the formation of hydroperoxides and headspace volatiles in the oil. TBHQ also protected tocopherols, especially α‐tocopherol, from oxidation. During long‐term room‐temperature (LTRT) storage, the changes in PV between the oils with and without TBHQ were similar, but the oil with TBHQ had lower headspace volatile contents than that without TBHQ. Headspace volatile analysis was more suitable than PV measurement for predicting the oxidative stability of soybean oil during LTRT storage. The contents of hexanal or (E)‐2‐heptenal in the oil at 1–5 days of accelerated storage could be used to predict those of the corresponding compound in the oil at 0–4 weeks of LTRT storage. Copyright © 2005 Society of Chemical Industry     

Impact of chitosan and oregano extract on the physicochemical properties of microencapsulated fish oil stored at different temperature

Fish oil is an excellent source of omega-3 fatty acids and is easily susceptible to oxidation. Microencapsulation is a commonly employed technique to protect fish oil against oxidation. In the present study, the potential of chitosan in combination with bovine gelatin and maltodextrin as wall material for microencapsulation of fish oil by spray drying was evaluated. To improve the oxidative stability of the fish oil microencapsulates, oregano (Origanum vulgare L) extract was added at 0.50 g/100 g of emulsion. The spray-dried powder showed a moisture content of 2.8 – 3.2 g/100 g of spray-dried powder. The powder contained spherical microparticles with different sizes as indicated by scanning electron microscope images. Encapsulation efficiency of microencapsulates ranged between 68.94% and 81.88%. Differential scanning calorimetry and Fourier-transformed infrared spectroscopy analysis of microencapsulates revealed the possible structural stabilization of core and wall material. The oxidative stability of fish oil microencapsulates were monitored under three different temperature (60°C, 28 ± 2°C, and 4°C). Incorporation of oregano extract minimized the generation of secondary and tertiary oxidation products as indicated by lower peroxide value and thiobarbituric acid reactive substance values compared to control. Overall, the results suggested that combination of chitosan along with bovine gelatin and maltodextrin as wall material improved the surface morphology of the microparticle and encapsulation efficiency, whereas incorporation of oregano extract in fish oil before spray drying enhanced the oxidative stability during storage.     

Blending of corn oil with black cumin (Nigella sativa) and coriander (Coriandrum sativum) seed oils: Impact on functionality, stability and radical scavenging activity

Blends (10% and 20%, w/w) of black cumin seed oil (BCSO) and coriander seed oil (CSO) with corn oil (CO) were formulated. Oxidative stability (OS) and radical scavenging activity (RSA) of CO and blends stored under oxidative conditions (60 °C) for 15 days were studied. By increasing the proportion of BCSO and CSO in CO, levels of polyunsaturated fatty acids (PUFA) decreased, while monounsaturated fatty acids (MUFA) content increased. Progression of oxidation was followed by measuring peroxide value (PV), conjugated dienes (CD) and conjugated trienes (CT). Inverse relationships were noted between PV and OS at termination of storage. Levels of CD and CT in CO, and blends, increased with increase in time. CO:BCSO and CO:CSO blends gave 12-22% and 26-36% inhibition of DPPH radicals, respectively. Oxidative stability of oil blends were better than CO, most likely as a consequence of changes in fatty acids and tocopherols’ profile, and minor bioactive lipids (e.g., sterols and phenolics) found in coriander and black cumin oils.     

Volatile Compounds and Chemical Changes in Ultrapasteurized Milk Packaged in Polyethylene Terephthalate Containers

The volatile compounds profile and chemical stability of ultrapasteurized 2% milk bottled in amber polyethylene terephthalate (PET) were studied along with its shelf life of 60 d at 5 °C. Identification of volatile compounds using a solid‐phase microextraction (SPME) technique with gas chromatography‐mass spectrometry was performed in situ in the commercial product. Chemical stability was determined by measuring dissolved oxygen, free sulfhydryl groups, ascorbic acid, and headspace oxygen. The classes of volatile compounds identified were ketones, aldehydes, hydrocarbons, fatty acids, alcohol, and miscellaneous compounds. Volatile compounds found consistently during the storage period were 2‐heptanone, methoxy‐phenyl‐oxime, decane, 1‐ethyl‐2,4‐dimethyl‐benzene, D‐limonene, 2‐nonanone, octanoic acid, dodecane, and 4‐(1,1,3,3, ‐tetramethylbutyl) phenol. Possible products of lipid oxidation, such as hexanal, octanal, and nonanal, were also positively identified. Chemical stability of PET‐bottled milk was demonstrated by the insignificant changes in pH or TA, with the exception of ascorbic acid concentration, which degraded in the product at 60 d of refrigerated storage. Sensory evaluation of the milk samples revealed that there is no noticeable oxidized or rancid off‐flavor at 60 d of storage.     

Oxidative stability of potato chips: effect of frying oil type,temperature and antioxidants

The effect of type of frying oil and temperature on the oxidative stability of potato chips during storage was studied. Cottonseed oil, soybean oil, olive kernel oil and palmolein were used as frying media. The chips were packaged in metallized cellophane bags and incubated at 63 °C. At definite time intervals the absorbed oil was extracted and analyzed for peroxide value, Totox number and conjugated diene content. Olive kernel oil and palmolein absorbed into the chips showed better stability, whereas soybean oil presented the higher oxidation rate. Frying temperature (170, 180 or 190 °C) did not affect the oxidation rate during storage, with the exception of conjugated diene formation which was greater for chips fried at 190 °C. Ground oregano or oregano extract, obtained by petroleum ether extraction, were added to the chips as antioxidants. Both retarded significantly the oxidation rate of the oil absorbed into the chips, with results comparable to tertiary butylhydroquinone (TBHQ) during storage at 63 °C for 7 days; however TBHQ proved significantly more effective after that time. © 1999 Society of Chemical Industry     

Quality predictive models for bovine liver during storage and changes in volatile flavors

Protein and fat oxidation are important factors that influence the quality of bovine liver. The objectives of this study were to investigate the degree of oxidation changes in bovine livers during 90d at different temperatures (?20°C, ?10°C, 0°C, 10°C, and 20°C), and to develop Arrhenius models to predict its degree of oxidation.Carbonyl, thiobarbituric acid (TBA), peroxide value (POV) as oxidation attributes of bovine liver during storage were measured at different time and the changes were kinetically modeled using the Arrhenius equation. The activation energies of carbonyl, (TBA) and (POV) were 27.48, 55.48, and 58.94 KJ/mol, respectively. The determination coefficients (R₂) were above 0.97 for all. In addition, volatile compounds in bovine liver and consumer acceptance of bovine liver pate with bovine liver as the final product were also measured. Among the volatile compounds, The content of aldehydes and ketones in bovine livers stored at different temperatures increased significantly (p < 0.05). Consumer acceptance of bovine liver indicates that consumers prefer bovine liver paste made from bovine liver stored at lower temperatures (below 0°C).     

Characterization of volatiles from cultured dairy spreads during storage by dynamic headspace GC/MS

The effect of storage time and storage temperature on the formation of volatile compounds in dairy spreads was investigated. Dairy spreads were stored for 10 weeks at -18, 5 and 20 °C, respectively, and analyzed after 0, 38, 54 and 67 days of storage. By means of a dynamic headspace GC/MS method using Tenax traps the dairy spreads were analyzed for volatile aromatic compounds. 61 components were identified and their relative content was followed during the storage period. Among these were four alcohols, 17 aldehydes, four esters, ten alkanes, 11 ketones and six lactones. A general increase in the concentration of most of the volatile compounds during storage was found. The content of volatile compounds in dairy spreads stored at -18 °C was nearly constant or showed a rather low increase in the content during the storage period. Storage at higher temperatures (5 and 20 °C) resulted in an increase in the content of most of the volatiles after 40 days of storage. The profiles obtained were subjected to multivariate data analysis to determine the volatiles potentially responsible for oxidized off-flavors in dairy spread. The volatiles were divided into three groups: one correlated with storage temperature and 5 °C, one with storage time and 20 °C and the last with storage time alone. Most of the volatiles were found in the highest concentration after storage at 20 °C, but the content of some volatiles was highest after storage at 5 °C.     

Comparison of microwave irradiation and conventional thermal heating on volatile profiles and degree of oxidation in corn oil

Volatile profiles and degree of oxidation in corn oils after microwave treatment for 50 min were compared to oils with conventional heating at 180°C for 4 h. Oil microwaved for 10 and 50 min showed a similar degree of oxidation compared to the oil heated at 180°C for 1 and 3 h, respectively, based on the primary and secondary oxidation products. However, the total volatile contents of 50 min-microwaved oil were significantly lower than that of corn oil heated for 1 h at 180°C (P < 0.05). Microwave treatment accelerated the rates of lipid oxidation by 4.6 times compared to 180°C thermal oxidation. Relatively short treatment with microwave irradiation may not provide sufficient time to generate volatiles from oil. Microwaved corn oil for 50 min had higher contents of hexanal and t-2-heptenal and lower contents of 2,4-decadienal and nonanal than the oils heated at 180°C for 3 h. Reactive oxygen species may be involved in volatile formation in microwave-irradiated oils.     

Effect of an Ethanol Extract from Summer Savory (Saturejae hortensisL) on the Stability of Sunflower Oil at Frying Temperature

The effect of the ethanol extract from Saturejae hortensis L on the oxidative and thermal processes occurring in sunflower oil during its high-temperature treatment (180°C) was investigated. The changes during simulated deep fat frying were monitored by determination of the oxidation stability at 100°C, as well as by determination of unchanged triacylglycerols. It was established that the addition of 1 and 5 g kg^-1 ethanol extract from S hortensis L leads to a decrease in the oxidative and thermal changes in the oil. The ethanol extract from S hortensis L improved the oxidative stability of sunflower oil even after 50 h at 180°C and it inhibited the oxidative processes more than the thermal processes under these conditions. © 1997 SCI.