An overview of effects of gamma radiation on the biological, physicochemical and nutritional parameters of oilseeds and oils.

PURPOSE: Gamma irradiation is a non-thermal method for prolonging the shelf-life of foods and it is a possible alternative technology for oilseeds. After harvest, the development of pests and microorganisms, as well as the reactions caused by enzymes reason numerous problems in the oilseeds. Gamma radiation is one of the methods that could inhibit undesired microorganisms, but it can also change the physicochemical and nutritive characteristics of oils. CONCLUSION: This paper is a brief review of recent publications on the effects of gamma radiation on the biological, physicochemical and nutritional parameters of oils. Overall, gamma radiation is a safe and environmentally friendly method that improves the quality, stability and safety characteristics of oilseeds and oils. In the future, there may also be many health reasons to produce oils using gamma radiation. Investigation of other radiation techniques such as x-rays and electron beams have a good potential once the specific doses that would free them from pests and contaminants have been identified while conserving the benefits without altering their sensory properties.

Nano-delivery systems for encapsulation of phenolic compounds from pomegranate peel.

Pomegranate fruit is getting more attention due to its positive health effects, and pomegranate peel (PP) is its main byproduct. PP has the potential to be converted from environmentally polluting waste to wealth due to its rich phenolic compounds such as ellagitannins, proanthocyanidins, and flavonoids with antioxidant, antimicrobial, and health effects. These phenolics are susceptible to environmental conditions such as heat, light, and pH as well as in vivo conditions of gastrointestinal secretions. Some phenolics of PP, e.g., ellagitannins could interfere with food ingredients and thus reduce their beneficial effects. Also, ellagitannins could form complexes with salivary glycoproteins, then a feeling of astringency taste. In this article, nano-delivery systems such as nanoparticles, nanoemulsions, and vesicular nanocarriers, designed and fabricated for PP bioactive compounds in recent years have been reviewed. Among them, lipid-based nano carriers i.e., solid lipid nanoparticles, nanostructured lipid carriers, and vesicular nanocarriers have low toxicity, large-scale production feasibility, easy synthesis, and high biocompatibility. So, it seems that the extraction and purification of bioactives from pomegranate wastes and nanoencapsulating them with cost effective and generally recognized as safe (GRAS) materials can be a bright prospect in enhancing the quality, safety, shelf life and health benefits of pomegranate products.

Properties of Pectin Extracted from Vietnamese Mango Peels.

This study was carried out to investigate the properties of pectin extracted from Vietnamese mango peels that have been discarded as waste. Three different mango cultivars named Hoa Loc, Ghep and Cat Chu at three different maturities were studied. Pectin extracted from immature, ripe and overripe stages ranged from 18.4 to 31.7 g/100 g dry weight (DW); the highest yields were obtained from the ripe fruits. Ghep peels contained the highest pectin amounts which ranged from 24.2 to 31.7 g/100 g DW, followed by Cat Chu (19.2 to 26.5 g/100 g DW) and Hoa Loc peels (18.4 to 24.1 g/100 g DW). Except for degree of esterification and emulsion capacity, other properties of the extracted pectin including water holding capacity, solubility and emulsion stability were significantly affected by the fruit maturation. Varieties, solubility, degree of esterification, emulsion activity and emulsion stability of the pectin isolated from the three cultivars ranged from 77.4% to 86.0%; 50.3% to 55.8%; 11.8% to 34.3% and 28.5% to 94.5%, respectively. Fourier-transform infrared results showed that almost all collected pectin samples could be classified as the high methoxyl pectin. Rheology data indicated viscosity of the isolated pectin was strongly dependent on temperatures.

Effect of roasting and microwave pre-treatments of Nigella sativa L. seeds on lipase activity and the quality of the oil.

The present research studied the thermal pre-treatment of non-soaked and soaked black seed (BS) by microwave radiation (1-3.5 min) in comparison with conventional roasting (2-8 min, 180 °C). As BS was treated for a longer time, a significant increase (p < 0.05) was observed in total chlorophylls, carotenoids and phenolic contents in the extracted oils. The oils obtained from the soaked seeds (to 8%) had significantly higher oil quality properties. The optimum extraction conditions were: irradiation time of 3.5 min and BS moisture content of 8%, which resulted in an extraction yield of 35.76%, 10643.730 caffeic acid equivalents/100 g, PV of 9.63 meq O2/kg and 18.88 h of Rancimat oxidative stability. The microwave pre-treatment was more effective than conventional roasting in reducing lipase activity. Based on the results obtained, it was advisable to treat BS with microwaves and soak them before extracting the oil in a cold press at room temperature.

Quality properties of puffed corn snacks incorporated with sesame seed powder.

Puffed corn snacks are tasty and affordable cereal-based food products which have a relatively poor nutritional quality. Sesame seed is a rich source of essential amino and fatty acids, phenolic compounds, tocopherols, and antioxidants. In this study, puffed corn snacks were produced by incorporating sesame powder at 0% (control sample), 5%, 10%, and 15% levels in its formulation and stored at room temperature (24°C) for 60 days. Fatty acid composition, tocopherol, sesamin and sesamolin, phenolic compounds, peroxide value (PV), acidity (AV), and sensory evaluation of the samples were determined. The results indicate that oleic acid content increased and palmitic acid decreased significantly (p < .05) in all the samples at 10% and 15% inclusion levels. The content of phenolic compounds, γ-tocopherols, sesamin, and sesamolin had significant increases in all the formulated samples. PV results indicated that the formulated samples had a higher stability when the ratio of sesame powder was increased, while the AV values showed a significant increase during storage. Incorporation of 10% sesame powder in the snack formulation had a positive effect on the stability, sensory, and nutritional quality of the product. This approach can be used to modify nutritional quality of this food product and introduce to food market as a relatively healthy snack.

Addition of calcium compounds to reduce soluble oxalate in a high oxalate food system.

Spinach (Spinacia oleracea L.) is often used as a base vegetable to make green juices that are promoted as healthy dietary alternatives. Spinach is known to contain significant amounts of oxalates, which are toxic and, if consumed regularly, can lead to the development of kidney stones. This research investigates adding 50-500mg increments of calcium carbonate, calcium chloride, calcium citrate and calcium sulphate to 100g of raw homogenates of spinach to determine whether calcium would combine with the soluble oxalate present in the spinach. Calcium chloride was the most effective additive while calcium carbonate was the least effective. The formation of insoluble oxalate after incubation at 25°C for 30min is a simple practical step that can be incorporated into the juicing process. This would make the juice considerably safer to consume on a regular basis.

Oxalate Content of the Herb Good-King-Henry, Blitum Bonus-Henricus.

The total, soluble and insoluble oxalate contents of the leaves, stems and buds of Good-King-Henry (Blitum Bonus-Henricus) were extracted and measured using HPLC chromatography. The large, mature leaves contained 42% more total oxalate than in the small leaves and the soluble oxalate content of the large leaves was 33% higher than the smaller leaves. Cooking the mixed leaves, stems and buds in boiling water for two minutes significantly (p < 0.05) reduced the total oxalate when compared to the raw plant parts. Pesto sauce made from mixed leaves contained 257 mg total oxalate/100 g fresh weight; this was largely made up of insoluble oxalates (85% of the total oxalate content). Soup made from mixed leaves contained lower levels of total oxalates (44.26 ± 0.49 mg total oxalate/100 g fresh weight) and insoluble oxalate made up 49% of the oxalate contents. The levels of oxalates in the Good-King-Henry leaves were high, suggesting that the leaves should be consumed occasionally as a delicacy because of their unique taste rather than as a significant part of the diet. However, the products made from Good-King-Henry leaves indicated that larger amounts could be consumed as the oxalate levels were reduced by dilution and processing.

Effect of Kimchi Fermentation on Oxalate Levels in Silver Beet (Beta vulgaris var. cicla).

Total, soluble and insoluble oxalates were extracted and analyzed by high performance liquid chromatography (HPLC) following the preparation of kimchi using silver beet (Beta vulgaris var. cicla) stems and leaves. As silver beet contains high oxalate concentrations and consumption of high levels can cause the development of kidney stones in some people, the reduction of oxalate during preparation and fermentation of kimchi was investigated. The silver beet stems and leaves were soaked in a 10% brine solution for 11 h and then washed in cold tap water. The total, soluble and insoluble oxalate contents of the silver beet leaves were reduced by soaking in brine, from 4275.81 ± 165.48 mg/100 g to 3709.49 ± 216.51 mg/100 g fresh weight (FW). Fermenting the kimchi for 5 days at 19.3 ± 0.8 °C in 5 L ceramic jars with a water airtight seal resulted in a mean 38.50% reduction in total oxalate content and a mean 22.86% reduction in soluble oxalates. The total calcium content was essentially the same before and after the fermentation of the kimchi (mean 296.1 mg/100 g FW). The study showed that fermentation of kimchi significantly (p < 0.05) reduced the total oxalate concentration in the initial mix from 609.32 ± 15.69 to 374.71 ± 7.94 mg/100 g FW in the final mix which led to a 72.3% reduction in the amount of calcium bound to insoluble oxalate.

Total, Soluble and Insoluble Oxalate Contents of Ripe Green and Golden Kiwifruit.

Three bulk samples of two different cultivars of kiwifruit, green (Actinidia deliciosa L.) and golden (Actinidia chinensis L.) were bought ripe, ready to eat from a local market. The aim of the study was to determine the oxalate composition of each of the three fractions of kiwifruit, namely skin, pulp and seeds. The pulp consisted of 90.4% of the edible portion of the two cultivars while the skin and seeds made up a mean of 8.0% and 1.6% respectively. Total oxalate was extracted with 2.0 M HCL at 21 °C for 15 min and soluble oxalates extracted at 21 °C in water for 15 min from each fraction. The total and soluble oxalate compositions of each fraction were determined using ion exchange HPLC chromatography. The pulp of golden kiwifruit contained lower amounts of total oxalates (15.7 vs. 19.3 mg/100 g FW) and higher amounts of soluble oxalates (8.5 vs. 7.6 mg/100 g FW) when compared to the green cultivar. The skin of the green cultivar contained lower levels of insoluble oxalates (36.9 vs. 43.6 mg/100 g FW), while the seeds of the green cultivar contained higher levels of insoluble oxalates 106.7 vs. 84.7 mg/100 g FW.

Mineral Analysis of Pine Nuts (Pinus spp.) Grown in New Zealand.

Mineral analysis of seven Pinus species grown in different regions of New Zealand; Armand pine (Pinus armandii Franch), Swiss stone pine (Pinus cembra L.), Mexican pinyon (Pinus cembroides Zucc. var. bicolor Little), Coulter pine (Pinus coulteri D. Don), Johann's pine (Pinus johannis M.F. Robert), Italian stone pine (Pinus pinea L.) and Torrey pine (Pinus torreyana Parry ex Carrière), was carried out using an inductively coupled plasma optical emission spectrophotometer (ICP-OES) analysis. Fourteen different minerals (Al, B, Ca, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, S and Zn) were identified in all seven varieties, except that no Al or Na was found in Pinus coulteri D. Don. New Zealand grown pine nuts are a good source of Cu, Mg, Mn, P and Zn, meeting or exceeding the recommended RDI for these minerals (based on an intake of 50 g nuts/day) while they supplied between 39%-89% of the New Zealand RDI for Fe. Compared to other commonly eaten tree-nuts New Zealand grown pine nuts are an excellent source of essential minerals.

Mineral analysis of mono-floral New Zealand honey.

The levels of 18 different minerals in ten locally produced mono-floral honeys (clover, honeydew, kamahi, manuka, nodding thistle, rata, rewarewa, tawari, thyme and viper's bugloss honey) were determined, as well as moisture content, pH, conductivity and colour. The most abundant minerals were potassium, phosphorus and calcium, ranging between 34.8-3640, 29.5-255 and 7.21-94.3mg/kg, respectively. Potassium made up 73% of the total mineral content. There was a large range of mean total mineral contents, with honeydew honey having the highest level (4060mg/kg) and viper's bugloss honey the lowest (126mg/kg). Honeydew had more than twice the mean total mineral contents than kamahi, the next highest. The heavy metal contents (Cd, Pb and Zn) of the mono-floral honey types investigated were very low. A strong positive relationship between mean conductivity and total mineral content (r(2)=0.973), and pH and total mineral content (r(2)=0.776) was observed in this study.

Oxalate content of silver beet leaves (Beta vulgaris var. cicla) at different stages of maturation and the effect of cooking with different milk sources.

The work presented here indicates that people who have a tendency to develop kidney stones should avoid consuming regrowth and developed silver beet (Beta vulgaris var. cicla) leaves. Soluble oxalate contents of leaves range from 58% of the total oxalate for the mature leaves up to 89% for the regrowth tissue, with regrowth tissue containing the highest levels of soluble oxalate at 7267+/-307 mg/100 g of dry matter (DM). Leaves cooked in milk contained significantly (p<0.05) lower levels of soluble oxalate compared to the leaves that were cooked in water. Leaves cooked in low fat milk contained significantly lower levels (p<0.05) of soluble oxalate (1.9%) than leaves cooked in standard milk (5.3%) or cream (6.3%). To maximize the reduction of soluble oxalate during the cooking of high oxalate foods such as spinach and silver beet, a low fat milk cooking medium with neutral pH should be utilized.

Release of antioxidant components from tomatoes determined by an in vitro digestion method.

Tomatoes are an important source of antioxidant compounds, such as lycopene, phenolics and ascorbic acid. The main objective of this study was to determine the accessibility (availability for absorption) of the antioxidant compounds (total phenolics, total flavonoids, lycopene, ascorbic acid) and the antioxidant activity in fresh tomatoes of three cultivars (Excell, Tradiro and Flavourine) grown in New Zealand. The tomatoes were subjected to an in vitro digestion method, in which the pH, temperature, enzymes and chemical conditions were maintained according to human gastrointestinal conditions. The results showed that a high amount of the total phenolics and total flavonoids (71-77%) were released from tomatoes during digestion. However, only 3.2-4.5% of the total lycopene was released. No ascorbic acid could be detected after completion of in vitro digestion, probably due to degradation. After completion of digestion, the in vitro digestion extracts were found to have 45-50% antioxidant activity compared with the total antioxidant activity of fresh tomatoes (as measured by the 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid diammonium salt radical decolourization assay). This study shows that the antioxidant components of tomatoes were affected by the in vitro digestion conditions depending on the type of compound. This in vitro digestion method gives an estimate of the release of antioxidant components in tomato, which may predict their in vivo behaviour.

An investigation of the antioxidant properties and colour of glasshouse grown tomatoes.

The colour and the antioxidant content of five different cultivars of tomatoes (Lycopersicon esculentum L.), grown in glasshouses using commercial hydroponic techniques, were measured in freshly harvested tomatoes and after 2 and 5 days of storage in the dark at 15 degrees C. The two cocktail cultivars of tomatoes, Aranca and Flavourine, were the smallest tomatoes but they contained higher dry matter contents compared with the three standard salad cultivars, Excell, Celero and Dutch Chaser. There were significant differences (P < 0.001) in lycopene (the major carotenoid), ascorbic acid and total antioxidant activity in the whole fruit of the five different cultivars evaluated at harvest, while the total phenolic contents were very similar. The lycopene levels of all the cultivars increased significantly (P < 0.001) after storage for 2 and 5 days at 15 degrees C. Overall, the total phenolic content of all the cultivars did not change appreciably after storage at 15 degrees C while the levels of ascorbic acid fell by 12.6% when stored for 5 days in the dark. There was a significant difference (P < 0.001) in the total antioxidant activity between the five different cultivars when freshly harvested; the highest levels of total antioxidant activity were observed in the two cocktail cultivars, Aranca and Flavourine. Antioxidant activity showed different patterns of change depending on cultivar. An increase in the total antioxidant values could be seen in cultivars Dutch chaser and Excell, after storage for 5 days at 15 degrees C. The total antioxidant activity values of Flavourine and Celero fell on storage while the values for stored Aranca were very similar to the values when freshly harvested. The skin colour, as shown by Commission Internationale l'Eclairage (CIE) L*a*b* values of each cultivar were markedly different at harvest even though each cultivar was harvested at the same maturity. The a* value of each cultivar increased significantly (P < 0.001) when they were stored in the dark, for either 2 or 5 days, at 15 degrees C. Regression analysis showed that overall there was no significant relationship (R(2) = 0.14) between the lycopene content and the a* value of all the tomatoes; however, when examined individually, the two cocktail tomatoes Aranca and Flavourine showed strong correlation-R(2) = 0.96 and R(2) = 0.97, respectively. Overall, the (a*/b*)(2) was the most reliable indicator of lycopene concentration (R(2) = 0.96) in the tomatoes examined in this study.

Bioavailability of soluble oxalate from spinach eaten with and without milk products.

Leafy vegetables such as spinach (Spinacia oleracea) are known to contain moderate amounts of soluble and insoluble oxalates. Frozen commercially available spinach in New Zealand contains 736.6+/-20.4 mg/100g wet matter (WM) soluble oxalate and 220.1+/-96.5mg/100g WM insoluble oxalate. The frozen spinach contained 90mg total calcium/100g WM, 76.7%of this calcium was unavailable as it was bound to oxalate as insoluble oxalate. The oxalate/calcium (mEq) ratio of the frozen spinach was 4.73. When frozen convenience food is grilled there is no opportunity for the soluble oxalates to be leached out into the cooking water and discarded. Soluble oxalates, when consumed, have the ability to bind to calcium in the spinach and any calcium in foods consumed with the spinach, reducing the absorption of soluble oxalate. In this experiment 10 volunteers ingested 100g grilled spinach alone or with 100g additions of cottage cheese, sour cream and sour cream with Calci-Trim milk (180 g) and finally, with 20g olive oil. The availability of oxalate in the spinach was determined by measuring the oxalate output in the urine over a 6-hour and 24-hour period after intake of the test meal. The mean bioavailability of soluble oxalate in the grilled spinach was 0.75+/-0.48% over a 6-hour period after intake and was 1.93+/-0.85% measured over a 24-hour period. Addition of sour cream and Calci-Trim milk reduced the availability of the oxalate in the spinach significantly (P<0.05) in both the 6-hour and 24-hour collection periods.

Oxalate content and calcium binding capacity of tea and herbal teas.

Thirty-two commercially available teas consisting of green, oolong and black teas were bought from supermarkets in Christchurch, New Zealand in June 2001. Fifteen herbal teas were also purchased at the same time. The soluble oxalate content of the infusate made from each of the teas was determined using high pressure liquid chromatography. The mean soluble oxalate contents of black tea in tea bags and loose tea leaves were 4.68 and 5.11 mg/g tea, respectively, while green teas and oolong tea had lower oxalate contents, ranging from 0.23 to 1.15 mg/g tea. The soluble oxalate content of the herbal teas ranged from not detected to 3.00 mg/g tea. A regular tea drinker consuming six cups of tea/day would have an intake of between 26.46 and 98.58 mg soluble oxalate/day from loose black tea, 17.88 and 93.66 mg soluble oxalate/day from black tea in tea bags and a maximum of 18.0 mg/day from herbal teas. The oxalate intake from the regular daily consumption of black teas is modest when compared to the amounts of soluble oxalate that can be found in common foods. However, oxalate in black teas has the potential to bind to a significant proportion of calcium in the milk, which is commonly consumed with the black teas.

Cholesterol oxides: their occurrence and methods to prevent their generation in foods.

Eight cholesterol oxides are commonly found in foods with high cholesterol content, such as meat, egg yolk and full fat dairy products. Factors known to increase the production of cholesterol oxides in foods are heat, light, radiation, oxygen, moisture, low pH, certain pro-oxidising agents and the storage of food at room temperature. Processes, such as pre-cooking, freeze-drying, dehydration and irradiation, have all been reported to result in increased production of cholesterol oxides in meats. As prepared consumer foods are becoming increasingly popular, the consumption of higher levels of cholesterol oxides in foods is inevitable. An understanding of the mechanisms involved in the generation of cholesterol oxides may assist in their reduction in foods and possibly reduce the impact of these compounds on human health.