Changes in volatile aroma compounds of organic fragrant rice during storage under different conditions

BACKGROUND: Aroma of fragrant rice greatly affects palatability as well as consumer acceptability. Loss of desirable volatile compounds such as 2‐acetyl‐1‐pyrroline (2‐AP) and increase in volatile lipid oxidation products in aged rice have been reported. The aim of this study was to monitor the changes in key volatile compounds of organic red fragrant rice cv. Hom Daeng during storage. Effects of packaging material, storage temperature and time were evaluated using solid phase microextraction/gas chromatography/mass spectrometry. RESULTS: Thirteen key volatile compounds including ten lipid oxidation products were monitored. For samples vacuum packed in Nylon/LLDPE pouches at ambient temperature, significant increases in hexanal, 2‐pentylfuran, 1‐octanol and 4‐vinyl guaiacol and significant decreases in 2‐AP and geranyl acetone were found after the second month (P?0.05). Vacuum packing in OPP/Al/LLDPE pouches or storage at 15 °C better retarded the formation of volatile lipid oxidation products and greater retained desirable odorants, including 2‐AP. However, accumulation of lipid oxidation products and 4‐vinyl guaiacol was apparent after the sixth month under these storage conditions. CONCLUSION: A greater extent and higher rate of undesirable changes in volatile compounds were found in samples stored under Nylon/LLDPE/ambient temperature condition. Nevertheless, this condition is acceptable for the retail trade of organic rice in Thailand. Storage conditions using reduced temperature or better packaging materials may be more appropriate for exported rice or superior‐grade fragrant rice to better maintain the desirable rice aroma. Copyright © 2010 Society of Chemical Industry     

发酵牦牛肉成熟过程中挥发性香气成分的变化

为探讨发酵牦牛肉挥发性香气成分在成熟过程中的变化规律,本文采用固相微萃取法（SPME）对各取样点样品中挥发性物质进行提取,利用气相-嗅闻-质谱联用法对其中的挥发性成分进行定性和定量分析。总计有84种挥发性成分被鉴定,其中,经嗅闻鉴定的香气活性化合物有48种,包括烃类（12）、醇类（8）、酮类（7）、醛类（3）、酸类（3）、含硫化合物（2）、酯类（4）、含氮类化合物（7）和酚类（2）。在成熟过程中,烃类和酮类含量整体呈现波动变化。醛类和酯类含量在成熟前期增加,而后又降低。酸类和吡嗪类形成于成熟过程,含量逐渐增加。烃类是成品发酵牦牛肉风味组成中含量最高的,其次是醇类、酮类及吡嗪类化合物。香辛料的添加、氨基酸的降解及微生物的代谢对发酵牦牛肉的香气形成具有重要作用。      

Changes in volatile aroma compounds of pineapple (Ananas comosus) during freezing and thawing

Changes in the volatile aroma compounds of pineapple (Ananas comosus) during freezing and thawing were compared against fresh samples to determine the effect of freezing on pineapple flavour. An HS‐SPME–GC–MS analysis showed that the Smooth Cayenne pineapple variety had nineteen volatile compounds, in four classes of compounds including fourteen esters, two hydrocarbons, two sulphur‐containing compounds and one lactone. The main characteristic volatile compounds of the fresh pineapple were methyl hexanoate, ethyl hexanoate, ethyl 3‐methylthiopropanoate and 1‐(E,Z)‐3,5‐undecatriene. Freeze–thaw cycles were associated with the loss of some volatile aroma compounds, particularly the esters which were found to be the main characteristic of fresh pineapples. The freezing and thawing process was found to cause damage to the pineapple tissues due to ice recrystallisation and dehydration which lead to the reduction of volatile aroma compounds.     

Qualitative analysis of the main aroma compounds associated with traditional Musalais processing in Xinjiang,China

Musalais has a unique flavour owing to the traditional technique of spontaneously fermenting the boiled substrates from compressed local grape juice and the grape residue. Liquid–liquid extraction followed by gas chromatography–mass spectrometry of 11 samples collected at different time points during the fermentation identified the aromatic compounds associated with traditional Musalais processing. The results showed that boiling completely destroyed the original aroma of the grape (16 compounds) and grape juice (16 compounds) and produced distinct furan‐derived compounds in the initial fermented substrates (10 compounds). During the fermentation, the aromatic compounds, with phenethyl alcohol as the major compound, accumulated within 24–40 days. Within a year of aging, over 40 compounds had increased and around half of these were esters, with ethyl caprylate, ethyl caprate, 2‐phenylethyl acetate and diethyl succinate as the major aromatic compounds. Boiling the grape derivatives, spontaneous fermentation and a short maturation time produced the three classes of aromatic components related to furans, alcohols and esters, respectively. These compounds contributed to the strong mellow flavour of fresh Musalais and the ester fragrance of a mature Musalais along with a distinctive caramel aroma. The results provide useful information on the origin of the flavours of Musalais wine and the associated wine‐making technology. Copyright © 2012 The Institute of Brewing & Distilling     

Vacuum-packed ripened sausages: evolution of volatile compounds during storage

BACKGROUND: Various studies have shown the ability of volatile compounds to influence the quality of charcuterie products because of their effect on sensorial properties. To the best of our knowledge, there are no data in the scientific literature concerning the evolution of volatile compounds of vacuum‐packed ripened sausages over time. The aim of this work was to evaluate the evolution of volatile compounds in vacuum‐packed ripened sausages over time, considering that this kind of packaging is the most commonly used to prolong the shelf‐life of these products. RESULTS: Sixty‐nine volatile compounds were identified. Those derived from spices represented the prevailing compounds at the beginning of storage and significantly decreased (P < 0.001) during 5 months of storage, as a result of the well‐known antioxidant activity. Conversely, compounds derived from the autoxidation of lipids, which are among those chiefly responsible of sensorial properties of meat products, significantly increased (P < 0.001). CONCLUSION: The research demonstrated that vacuum packaging influenced the evolution of volatile compounds during storage of ripened sausages. In particular, the increase of volatile compounds derived from autoxidation of the lipid fraction indicated that oxidative processes involved the fatty fraction of ripened sausages also in the scarcity of oxygen. Copyright © 2011 Society of Chemical Industry     

Changes in bioactive compounds and antioxidant activity during convective drying of murta (Ugni molinae T.) berries

Murta (Ugni molinae T.) berries were air‐dried at five temperatures (40, 50, 60, 70 and 80 °C), and the changes in β‐carotene, phenolic acids, total phenolic and flavonoid contents and antioxidant capacities (DPPH and ORAC) were investigated. The berries showed a high content of β‐carotene, which decreased during drying temperature between 40 °C and 80 °C. Free and bound phenolic acids were also determined, showing gallic acid to be the prevalent phenolic acid. Total phenolic and flavonoid contents in the dried berries showed a higher decrease at lower temperature due to longer drying time. The radical‐scavenging activity also showed higher antioxidant activity at higher drying temperatures (70–80 °C) than at lower drying temperatures (40–50 °C). Total phenolic content (TPC) and flavonoids showed good correlation with antioxidant capacity. Murta berries proved to be an excellent source of antioxidants and bioactive compounds and are therefore a potential ingredient for new functional food products.     

不同贮藏条件下青花椒香气成分的比较

以重庆江津青花椒为原料,采用水蒸气蒸馏法提取精油,并用气相色谱-质谱联用仪(GC-MS)分析,比较在低温密封避光与室温未密封不避光2种贮藏条件下青花椒香气成分的变化。结果表明:贮藏前干青花椒挥发油含量为17.49%,贮藏后干青花椒挥发油的含量分别为15.97%(低温密封避光贮藏)和9.87%(室温未密封不避光贮藏),低温密封避光贮藏能有效延缓挥发油的损失;贮藏前后干青花椒挥发油中共鉴定出31种成分,贮藏前后共有成分24种,贮藏前后干青花椒挥发油中的主成分均为香桧烯、月桂烯、(+)-萜二烯、芳樟醇、反式橙花叔醇,但其含量因贮藏条件的不同而存在差异,不同贮藏条件下干青花椒挥发油中损失与新产生的微量成分略有差异,低温密封避光贮藏可有效保持干青花椒原有的香气。     

四川白口仔姜在贮藏过程中挥发性成分的变化

为研究仔姜在沙土贮藏过程中挥发性风味物质的变化,将采收的仔姜经过挑选、分级、杀菌处理后埋藏在沙土中,并于11℃贮藏,采用固相微萃取—气相色谱—质谱联用测定不同时期贮藏过程中仔姜的挥发性风味物质。结果表明:贮藏过程中从仔姜中共检测出77种挥发性成分,分别为烃类(47种)、醇类(16种)、酮类(1种)、醛类(4种)、醚类(9种),其中烃类、酮类物质总量在贮藏过程中(10,20,30d)无显著差异(P0.05),醇类物质总量在20d时显著降低,30d后显著升高。贮藏过程中仔姜有10种挥发性成分的含量随着贮藏时间延长显著升高,分别为左旋-α-蒎烯、莰烯、2,6-二甲基-2,6-辛二烯、反-β-金合欢烯、别香橙烯、2-茨醇、α-松油醇、香茅醇、香茅醛、柠檬醛,在30d时这些物质含量分别是新鲜样品的5.09,7.89,6.73,10.48,153.75,11.11,8.21,11.73,24.96,14.65倍。