Volatile profiles of aromatic and non-aromatic rice cultivars using SPME/GC–MS

Rice (Oryza sativa L.) is enjoyed by many people as a staple food because of its flavour and texture. Some cultivars, like scented rice, are preferred over others due to their distinctive aroma and flavour. The volatile profile of rice has been explored by other investigators, some of whom have also determined a corresponding aroma using GC/olfactometry. However, little research has been done to determine if different aromatic rice cultivars produce different flavour volatiles that would make them more desirable than others when cooked. In this study, seven aromatic and two non-aromatic cultivars were examined for their volatile profiles both before and after storage using solid phase microextraction (SPME) fibres in conjunction with gas chromatography/mass spectrometer (GC–MS). Ninety-three volatile compounds were identified, 64 of which had not been previously reported in rice. Differences were found in the volatile compounds of aromatic and non-aromatic rice besides 2-acetyl-1-pyrroline (2-AP). Most of the volatile compounds were present in freshly harvested rice and rice following storage, with very few new compounds being identified only after storage. Dellrose, an aromatic cultivar, and Cocodrie, a non-aromatic cultivar, had the most complex volatile profiles (over 64 volatiles). Sixteen compounds were found only in the aromatic cultivars, and some volatiles were found to be unique to specific aromatic cultivars. However, no distinctive pattern was observed that would identify a cultivar as being derived from Basmati, Khao Dawk Mali 105 (i.e. jasmine), or other sources of aroma. This study showed that there is a great diversity of volatiles in both aromatic and non-aromatic rice cultivars and, with further research, this may lead to a better understanding of the combination of compounds that gives a cultivar a unique flavour.     

Changes to physicochemical properties and aroma of irradiated rice

Gamma-irradiation at dosages of 0.2-2.0 kGy controlled insects in packaged aromatic milled rice (KDML-105). However, it induced changes in physicochemical properties of the rice. Decreases in some pasting parameters, increases in water absorption and total solids in cooking water, and decreased cooked rice hardness showed that starch granules of milled rice were changed by irradiation. Alterations of the granular structure of starch were seen by scanning electron microscopy. These changes affected the texture of the cooked rice. In addition to an increase in yellowness (b-value) and an increase in lipid oxidation (TBA, thiobarbituric acid) and a decrease in volatile compounds (ACPY, 2-acetyl-1-pyrroline), irradiation contributed to changes in the colour and aroma of irradiated cooked rice. Gamma dosage had a significant positive correlation (P<0.01) with the b-value, pasting properties and a negative correlation with cooked rice hardness and ACPY content. Panelists responded to these changes with less perception of sensory qualities. Maximum doses of less than 1.0 kGy should be used to disinfest aromatic rice although when considered strictly on aroma, less than 0.5 kGy would be more suitable.     

The use of spray drying to microencapsulate 2-acetyl-1-pyrroline, a major flavour component of aromatic rice

Summary Different ratios of gum acacia and maltodextrins were used to investigate the appropriate wall materials for encapsulation, by spray drying, of 2‐acetyl‐1‐pyrroline (ACPY). This compound, which is the major flavour component of aromatic rice, was extracted from pandan (Pandanus amaryllifolius) leaves by steam distillation. The amounts of ACPY before and after spray drying encapsulation were not significantly different (P < 0.05). Better retention of ACPY was obtained by encapsulation. In its liquid form ACPY degraded quickly as 63% reduction occurred in a basic solution after 7 days; however, only 30% reduction was found in acidic solution after 35 days of storage. After 72 days of storage, the amount of ACPY in encapsulated powders made with differing amounts of gum acacia and maltodextrin decayed as follows: ratios of gum acacia:maltodextrin of 70:30, 60:40, 50:50, 40:60, 30:70 and 0:100 gave the following amounts of degradation of 27.7, 33.4, 43.2, 35.7, 30.6 and 32.6% respectively. Encapsulation in 70:30 gum acacia:maltodextrin gave the best retention of ACPY.     

Influence of CMC‐ and guar gum‐based silver nanoparticle coatings combined with low temperature on major aroma volatile components and the sensory quality of kinnow (Citrus reticulata)

Aroma profile and organoleptic quality of CMC‐ and guar gum‐based silver nanoparticle‐coated kinnow (Citrus reticulata cv. Blanco) was evaluated for 120 days at 4 °C and 10 °C, 85–95% relative humidity. Loss in three major aroma‐active volatile compounds (limonene, linalool and γ‐terpinene) was determined after every 15 days by GC‐MS. Sensory quality of coated and uncoated fruit stored at 10 °C was declined during storage. Twenty five volatile aroma compounds were identified in fresh kinnow juice. Guar gum‐Ag coatings and 4 °C storage has significantly reduced losses of limonene, linalool and γ‐terpinene contents from 91 to 23%, 99 to 10% and 97 to 29% respectively as compared to uncoated fruit stored at 10 °C. Study suggests that CMC‐ and guar gum‐based silver nanoparticle‐coated kinnow stored at 4 °C has preserved the fruit aroma and sensory quality for 120 days.     

葡萄酒香气化学研究进展

葡萄酒的整体香气主要取决于气味物质之间以及气味物质与非芳香基质成分的复杂反应。对葡萄与葡萄酒香气的化学研究,主要集中于对风味起作用的挥发性芳香物质的复杂性,以及不同葡萄品种、种植区和年份引起的变化。本文对葡萄酒中香气成分的种类、影响因素、分析方法及其应用进行综述。     

CONTROLLED ATMOSPHERE STORAGE AND EDIBLE COATING EFFECTS ON STORAGE LIFE AND QUALITY OF TOMATOES

Tomatoes at pink stage maturities were coated with Semperfresh^TM edible fruit coating which is composed of sucrose esters of fatty acids, sodium carboxymethyl cellulose and mono-diglycerides of fatty acids. One group of coated and uncoated tomatoes were stored at 23 × 2C under air atmosphere, another group was stored at 12C under air atmosphere and third group was stored at 12C, 93–95% RH in a controlled atmosphere (CA) containing 3% CO₂, 3% O₂ and 94% N₂. Samples of tomatoes were analyzed for firmness, weight loss, titratable acidity, pH, soluble solids, sugars, ascorbic acid and lycopene to examine changes in quality during storage. Semperfresh^TM edible fruit coating was found to be significantly effective at both storage temperatures (23 × 2C and 12C) in air to delay changes in firmness, titratable acidity, pH, soluble solids, sugars, ascorbic acid and lycopene. Semperfresh^TM fruit coating reduced fruit weight loss as compared to fruit without coating but the difference between coated and uncoated tomatoes was not significant. Shelf-life of pink tomatoes was increased 3 days at 23 × 2C and 6 days at 12C in air by coating. CA storage delayed compositional changes in tomatoes significantly as compared to air storage of coated and uncoated tomatoes. CA storage also had a significant potential for reducing weight loss and microbial spoilage. Tomatoes were stored 40 days in CA. Coated and uncoated tomatoes exhibited the same results in CA.     

Aroma characterisation and UV elicitation of purple basil from different plant tissue cultures

Exposure to stressful environmental conditions can induce severe metabolic variations in basil (Ocimum basilicum) aroma. The aromatic profiles of Dark Opal and Red Rubim varieties (in vivo plants, in vitro shoots, callus, and suspension cultures) were investigated for the first time. The established calli represented the most interesting miniaturised aromatic plant systems, as they were able to emit many typical basil volatiles with very low amounts of phenylpropanoids (1–2%). The hydrocarbon monoterpenes and oxygenated volatiles emitted from calli of both varieties were greatly and conversely affected by UV-C and UV-B, in comparison with the non-irradiated samples. As calli of both varieties still maintained very low levels of phenylpropanoids even after UV elicitation, they might be regarded not only as efficient in vitro plant models to study volatile compounds under UV stress conditions, but also as safe aromatic biomass in comparison with in vivo basil plants.     

Alginate coating as carrier of oligofructose and inulin and to maintain the quality of fresh-cut apples

The aim of this study was to apply an edible coating containing prebiotics such as oligofructose and inulin to fresh-cut apple wedges. An assessment of the quality, sensory, polyphenol, and volatile attributes of coated and uncoated fresh-cut apple wedges was also undertaken. Fructan analysis showed that all prebiotics remained stable over the 14-d storage period and an intake of 100 g of apple supplies 1 to 3 g of prebiotics. Browning index, firmness, acidity remained stable throughout the 14 d compared to the control while applying prebiotic coatings resulted in an increase in soluble solids. Sensory and visual assessment indicated acceptable quality of apple wedges coated with prebiotics. HPLC analysis showed that levels of polyphenolic compounds were more stable in coated apple wedges (without prebiotic inclusions) than in uncoated control apples. No difference was found between O(2) and CO(2) headspace concentration of coated and uncoated samples. Significant differences (P < 0.001) were found for headspace volatile production between the samples. Most coated samples showed lower volatile production in the headspace than uncoated samples.     

Extraction and in vitro antioxidant capacity evaluation of phenolic compounds from pigmented aromatic rice (<Emphasis Type="Italic">Oryzae sativa</Emphasis> L.) cultivars

The aroma generating volatile components profile and in vitro antioxidant capacities of different aromatic rice cultivars was determined by GC–MS analysis and in terms of DPPH scavenging activity, lipid peroxidation inhibition, phosphomolybdenum reduction and reducing power assay. The total phenolic content including both free and bound forms in the analyzed aromatic rice cultivars, Mushki budgi (1.62 mg GAE/g), Mushki kandi (1.63 mg GAE/g) and Kamad (1.60 mg GAE/g) were found double the amount as compared to non-aromatic Koshkari (0.86 mg GAE/g) cultivar. The aromatic rice cultivars had also shown higher total flavonoid content and antioxidant activity than non-aromatic rice cultivar (Koshkari). The GC–MS results indicated 21-aromatic compounds present in sufficient quantities in aromatic cultivars and some of them were unique to these cultivars. Among the compounds identified, aldehydes were found in higher quantity followed by alkanes, ketones and esters. Among the aromatic rice cultivars, Mushki budgi and Mushki kandi were found possessing higher quantity of flavoring components such as benzaldehyde, a carcinostatic agent. The cultivars Mushki budgi and Mushki kandi indicated positive correlation of TPC, TFC and the in vitro antioxidant components largely, while the less aromatic Kamad, correlate with only two components viz DPPH and lipid peroxidation.     

Efficiency of dietary sodium alginate coating incorporated with lycopene in preserving rainbow trout

The main aim of this study was to investigate the effect of alginate coating without or with lycopene at levels of 0.5, 1, 1.5, and 3% on the quality of rainbow trout stored under refrigerated conditions for 16 days. Samples coated with alginate with or without lycopene showed significantly lower free fatty acid (FFA) and total volatile basic nitrogen (TVB-N) values compared to uncoated (control) filets, particularly after day 4. Moreover, significant differences (p < 0.05) were observed between the coated samples containing lycopene and samples not containing lycopene on the last day. In relation with pH, none of the treatments resulted in significant differences. In regard to oxidation parameters, the effect of alginate-lycopene coatings was only seen on day 16 of storage. In general, although alginate-lycopene coating had no significant effect on the reduction of thiobarbituric acid and peroxide values, it succeeded in decreasing the TVB-N and FFA values.     

Development of a single kernel analysis method for detection of 2-acetyl-1-pyrroline in aromatic rice germplasm

Because of the high demand for aromatic rice cultivars that command a premium, it is important to have efficient methods for determining 2-acetyl-1-pyrroline (2-AP), the aromatic compound found in rice, that can be used in breeding efforts and to detect aromatic/non-aromatic blended rice in the marketplace. Solid-phase microextraction (SPME) in conjunction with GC/MS was used to distinguish non-aromatic rice (Oryza sativa, L.) kernels from aromatic rice kernels. In this method, single kernels along with 10 μl of 0.1 ng μl⁻¹ 2,4,6-Trimethylpyridine were placed in sealed vials and heated to 80 °C for 18 min. During the heating stage volatile compounds, which include 2-AP, were adsorbed onto a SPME fiber. Volatiles were desorbed from the fiber and separated using gas chromatography. 2-AP was quantitated by mass spectrometry using the 111, 83 and 68 m/z ions. The method detected 2-AP in milled rice and brown rice; however, its detection in paddy rice was less successful. In a mixture of aromatic and non-aromatic rice, the aromatic rice kernels were differentiated from the non-aromatic rice kernels using the described method. Therefore, this method can be used to identify segregating from non-segregating progeny during early generations in an aromatic rice breeding program when quantities of seed are very limited and can determine if aromatic rice has been adulterated with non-aromatic rice either through inadvertent mixtures, outcrosses or prepared blends.     

大米及其衍生食品风味物质的研究进展

大米作为我国主要成品粮,风味及品质备受关注。不同品种和产地的大米,具有其独特的风味。对比目前提取大米风味物质的方法（溶剂萃取法、同时蒸馏法、固相微萃取法、吹扫捕集法、超临界萃取法等）;探讨大米风味物质的产生机制,不同稻谷品种、生长环境、储存条件、直链淀粉含量、蒸煮方法、浸泡时间等都会对大米风味产生影响,目前尚未明确挥发性物质与香气的关系,但普遍认为2-AP是区别香型和非香型大米的标志性物质;阐述一些大米衍生食品的风味物质、加工方式及其产生机制等。为大米风味物质的回收及应用提供一定参考及理论基础。     

南方香粳稻挥发性物质的指纹图谱分析

为研究我国南方香粳稻香味特点,本研究以南粳46、香软玉为实验材料,以茉莉香、巴斯马蒂、象牙香占、稻花香2号为对照,采用GC-IMS对其挥发性物质进行指纹图谱解析,深入分析我国南方香粳稻中挥发性物质与其它香稻品种的差异。研究发现：南方香粳稻香软玉、南粳46与茉莉香、巴斯马蒂和象牙香占中的挥发性物质具有较大差异。香软玉、南粳46中2-乙酰基-1-吡咯啉含量显著高于其它香稻品种。此外,香软玉、南粳46中2-正戊基呋喃、3-甲基丁酸乙酯、1-庚醇、反-2-庚烯醛、反-2-戊烯醛、反-2-己烯醛、1-戊醇、2-庚酮和戊醛等物质的含量显著高于其它香稻品种。本研究有助于揭示我国南方香粳稻的香味特点。     

含五倍子水提物的魔芋葡甘聚糖涂膜液对冷鲜猪肉的保鲜效果研究

本文以水为溶剂提取获得五倍子水提物并测定其总酚及总黄酮含量、抗氧化及抗菌活性,以及将五倍子水提物添加至魔芋葡甘聚糖溶液中对猪肉进行涂膜保鲜。在体外实验中,五倍子水提物可清除2,2-联氮-二（三-乙基-苯并噻唑-6-磺酸）二铵盐（ABTS）自由基,且对金黄色葡萄球菌和大肠杆菌具有抑制作用。将添加五倍子水提物的魔芋葡甘聚糖（KGM）涂膜液对冷鲜猪肉进行涂膜,能延缓冷鲜猪肉中菌落总数、硫代巴比妥酸（TBARS）值、p H以及颜色的变化。以菌落总数为参考指标,富含五倍子水提物的涂膜处理的冷鲜猪肉与未经涂膜处理的冷鲜猪肉对比,在4℃储藏条件下货架期延长5 d。含五倍子水提物的魔芋葡甘聚糖涂膜对冷鲜猪肉具有保鲜效果。      

EATING QUALITY OF “FUJI” APPLES AFFECTED BY A PERIOD OF COLD AIR AFTER ULO STORAGE

ABSTRACT

Over two subsequent seasons, emission of volatile compounds, consumer acceptability and quality parameters were analyzed in “Fuji” apples. In both seasons, apples were harvested at the same maturity stage and stored for 19 or 30 weeks at 1C and 92% relative humidity under an ultralow oxygen (ULO) atmosphere (1% O₂ + 1% CO₂) or under an ULO atmosphere followed by different periods (2 or 4 weeks) in cold air. The results revealed, for both seasons, that 4 weeks of cold air storage after ULO storage helped to increase the emission of some volatile compounds for both storage period, including characteristic volatile compounds for the variety, and did not have a negative effect on quality parameters. Additionally, the consumer acceptability was superior for those fruits.

PRACTICAL APPLICATIONS

It is well known for various apple varieties that long‐term storage under ULO conditions reduces volatile production resulting in poor flavor and aroma compared with fruits stored in air. Consequently, there is often dissatisfaction among consumers with the flavor of fruits which have been subjected to cold storage. The strategy that is proposed in the present work could be recommended to enhance the aromatic quality of fruit provided by the apple industry and, in consequence, increase its acceptability by consumers.     

Effects of Gellan-Based Edible Coating on the Quality of Fresh-Cut Pineapple During Cold Storage

The effects of gellan-based [gellan gum 0.56 % (w/v), glycerol 0.89 % (w/v) and sunflower oil 0.025 % (w/v)] edible coating on the respiration rate, physico-chemical properties and microbiological and sensory quality of fresh-cut pineapple during 16 days of storage (5?±?1 °C, 85?±?10 % RH) were evaluated. Uncoated fresh-cut pineapple was stored under the same condition and served as the control. For cross-linking reaction which was necessary for gel formation of gellan gum, a 2 % (w/v) calcium chloride solution that contained 1 % (w/v) ascorbic acid and 1 % (w/v) citric acid (as antibrowning agents) was used. The results obtained show that the respiration rate and weight loss of gellan-based coated samples were significantly (p?<?0.05) lower than those of the uncoated samples during 16 days of storage at 5 °C. In addition, coated samples significantly (p?<?0.05) maintained the firmness and colour of fresh-cut pineapple during low-temperature storage as compared to uncoated samples. The results obtained in this study also indicate that pH, titratable acidity and total soluble solids of coated and uncoated samples showed little changes during 16 days of storage at 5 °C. Gellan-based formulation did not show any antimicrobial effect, and no significant (p?>?0.05) differences were found among total plate counts and yeast and mould counts for coated and uncoated samples. Total plate counts and yeast and mould counts for coated and uncoated samples reached 10⁶ CFU/g (limit of shelf life acceptance for fruit-based products recommended by the Institute of Food Science and Technology in the UK) after 12 days of storage at 5 °C. In addition, the scores for all sensory characteristics at day 12 were significantly (p?<?0.05) higher in coated samples as compared to control. Therefore, the results obtained in this study indicate that gellan-based edible coating formulation has the potential to maintain the quality of fresh-cut pineapple during low-temperature storage for about 12 days.     

Oil Coating Affects Internal Quality and Sensory Acceptance of Selected Attributes of Raw Eggs during Storage

Four (coconut, palm, rice bran, and soybean) edible oils and glycerol were applied on eggshell. All noncoated and coated eggs were stored for 5 wk at 25 ± 2 °C and drawn weekly for quality evaluation. All oil coatings were more effective in preserving internal quality of eggs than was glycerol coating. As storage time increased, the preservative effects of edible oil coating on weight loss, and albumen and yolk quality were significantly noticed. Oil‐coated eggs had significantly lower weight loss (<0.43%) than did noncoated (3.87%) and glycerol‐coated (3.73%) eggs after 5 wk of storage. Based on the Haugh unit, oil‐coated eggs maintained AA grade up to 3 wk. After 5 wk of storage, noncoated, glycerol‐coated, and oil‐coated eggs changed from AA grade to below B, below B and A grade, respectively. The albumen pH of noncoated and glycerol‐coated eggs considerably increased from 8.23 to 9.51 and 9.42, respectively, while those of oil‐coated eggs either maintained or slightly increased to 8.32. The albumen viscosity of all eggs decreased with increased storage time. Consumers (N = 120) could differentiate surface glossiness of oil‐coated eggs from uncoated eggs (R‐index of 81.42% to 86.99%). All oil‐coated eggs were acceptable for surface glossiness (liking scores of 6.22 to 6.77) and surface odor (liking scores of 6.20 to 6.55) with overall liking scores of 6.34 to 7.03. Overall, this study demonstrated that edible oil (coconut, palm, rice bran, and soybean) coating could preserve internal quality of eggs (maintaining grade A) at least 4 wk longer than noncoated eggs. Practical Application: Freshness is a major contribution to the egg quality. The internal quality of eggs begins to deteriorate after they have been laid due to loss of moisture and carbon dioxide via the eggshell pores. Refrigeration is very effective in preserving egg quality. Surface coating is an alternative method to preserve egg quality, although it is much less effective than refrigeration. This study demonstrated that coconut, rice bran, soybean, and palm oils, which are abundant and commonly consumed in many parts of the world, could preserve the internal quality and reduce weight loss of oil‐coated eggs during room temperature storage.     

PET trays coated with Citrus extract exhibit antioxidant activity with cooked turkey meat

A natural Citrus extract with potential antioxidant activity was evaluated as an ingredient for the production of active food packaging. The extract, in methanol, was sprayed onto the surface of polyethylene terephthalate (PET) trays. For comparison, a second set of trays were prepared using α-tocopherol as the coating. The effectiveness of the two types of packaging in delaying lipid oxidation in cooked turkey meat slices, stored at 4 °C over 4 days, was compared using 2-thiobarbituric acid-reactive substances (TBARS) and hexanal assays. TBARS and hexanal values, for meat stored on the Citrus extract coated trays, were significantly lower (P < 0.01) than those of meat stored on uncoated (control) trays while α-tocopherol coated trays exhibited no significant effect compared to control trays (P > 0.05). The effectiveness of the Citrus extract coating, compared to the α-tocopherol coating, was attributed to its higher surface roughness, demonstrated by optical profilometry, and the higher level of release (solubility) of the antioxidant in water.     

Chemical Constituents and Post-Harvest Prospects of Pandanus amaryllifolius Leaves: A Review

The leaves of Pandanus amaryllifolius Roxb. are widely used for flavoring food items. Extensive work has been done on agro parameters and propagation techniques as well as isolation and identification of the important chemical constituents such as volatile compounds, proteins, alkaloids and flavonoids. This review focuses on the possibilities of using the leaves in food and nonfood industries with particular reference to its aroma component. The major aromatic compound, 2-acetyl-1-pyrroline, has commercial significance as a flavor constituent that imparts the characteristic aroma of scented rice varieties such as basmati rice in India and in several Asian rice varieties. The compound can be added to nonaromatic rice varieties and other food formulations. The location and concentration of 2-acetyl-1-pyrroline in both Pandanus amaryllifolius and aromatic rice has been studied, as has the feasibility of extraction of 2-acetyl-1-pyrroline using different methodologies. The different methods for processing and preservation of this flavor compound are reviewed as are the application potential for flavor enrichment. Further, the therapeutic value of Pandanus amaryllifolius leaves and their importance in other areas as a source of phytochemicals and insecticide has also been documented.