Proton nuclear magnetic resonance rapid and structure-specific determination ofω-3 polyunsaturated fatty acids in fish lipids

Based on proton nuclear magnetic resonance (¹H-NMR) spectroscopy, a rapid and structure-specific method for the determination of ω-3 polyunsaturated fatty acids (PUFAs) in fish lipids is presented. The different chemical shift observed for the methyl resonance of ω-3 PUFAs (δ=0.95 ppm) with respect to the methyl resonance of all other fatty acids (δ=0.86 ppm) has provided the possibility of proposing a new and rapid method for the determination of ω-3 PUFA content. Twenty-four fish lipid samples (raw, cooked and canned albacore tuna) produced results that showed good agreement between¹H-NMR analysis and gas chromatographic determination. Raw and cooked samples showed significantly higher levels of ω-3 PUFA than canned tuna.     

传统风味卤腌熟肉制品软包装保存研究

本试验以五香卤肉和川味香肠为代表，对传统风味的卤腌熟肉制品进行了软包装保存的研究。内容包括复合袋优选、杀菌条件确定及工艺学试验，对热杀菌后引起的产品质地酥软及成品存放中脂肪的析出问题作了探讨，并分析了成品的主要指标，进行了商业无菌检验。     

Effect of rice ageing and freeze‐thaw cycle on textural properties of cooked rice (Oryza sativa L.) cv. Khao Dawk Mali 105

This study investigated the effect of rice grain ageing (0.7–12 months) and freeze‐thaw 1–5 cycles on the textural properties of cooked rice. The cooked rice from aged rice grains was freezing and thawing up to five cycles. Ageing of the rice grain increased the hardness and decreased the stickiness of the cooked rice. Repeated freeze‐thaw cycles caused an increase in hardness and a decrease in stickiness of aged cooked rice. Scanning electron micrographs showed a rough surface on the cooked rice after repeated freeze‐thaw cycles, especially for cooked rice from rice aged for 12 months. Differential scanning calorimetry and X‐ray diffraction showed increased starch retrogradation with increased freeze‐thaw cycles. The gelatinisation temperature and gelatinisation enthalpy increased when rice was aged for longer periods. Thus, ageing of rice and the number of freeze‐thaw cycles influence the textural properties of cooked rice.     

Contribution of water and cooked rice to an estimation of the dietary intake of inorganic arsenic in a rural village of West Bengal,India

Arsenic contamination of rice plants by arsenic-polluted irrigation groundwater could result in high arsenic concentrations in cooked rice. The main objective of the study was to estimate the total and inorganic arsenic intakes in a rural population of West Bengal, India, through both drinking water and cooked rice. Simulated cooking of rice with different levels of arsenic species in the cooking water was carried out. The presence of arsenic in the cooking water was provided by four arsenic species (arsenite, arsenate, methylarsonate or dimethylarsinate) and at three total arsenic concentrations (50,?250 or 500?µg?l^?1). The results show that the arsenic concentration in cooked rice is always higher than that in raw rice and range from 227 to 1642?µg?kg^?1. The cooking process did not change the arsenic speciation in rice. Cooked rice contributed a mean of 41% to the daily intake of inorganic arsenic. The daily inorganic arsenic intakes for water plus rice were 229, 1024 and 2000?µg?day^?1 for initial arsenic concentrations in the cooking water of 50, 250 and 500?µg?arsenic?l^?1, respectively, compared with the tolerable daily intake which is 150?µg?day^?1.     

Thawing Prior to Cooking Affects Sensory, Shear Force, and Cooking Properties of Beef Patties

Patties from 6 commercial formulations were cooked to 71°C from either the frozen state or after thawing for 24 to 27 h at 4 °C to eliminate the pink/red color exhibited when cooked to 71 °C from the frozen state. Thawed patties had shorter cooking times, higher cooking yields, and lower shear force peak load and peak energy values. Patties cooked from the thawed state increased in thickness during cooking, while patties cooked from the frozen state decreased in thickness during cooking. Thawing prior to cooking increased sensory evaluation scores except for patties made with carrageenan. Thawing not only eliminated the problem of pink/red color after cooking but also improved sensory, shear force, and cooking properties of beef patties.     

低温熏煮香肠的贮藏特性研究

对低温熏煮香肠在7℃贮藏条件下的感官、理化和微生物指标进行了研究。结果表明,随贮藏时间的延长,样品感官变化陆续表现为“空皮”、“出水、出油”和“胀袋”等腐败特征,同时伴有酸味、臭味等异味产生。随贮藏时间的延长,样品pH下降;TVB-N值先上升,后下降;TBARS值先上升,后下降;腐败微生物菌群的细菌总数消长规律为贮藏初期细菌总数缓慢上升,随后急剧上升,然后趋于稳定,最后下降。表明腐败微生物的生长繁殖和致腐是影响低温熏煮香肠产品质量和货架期的主要因素。     

Free D-amino acids determination in ready-to-eat cooked ham irradiated with electron-beam by indirect chiral HPLC

Potential racemization of L-amino acids (AA) in ready-to-eat (RTE) cooked ham after hygienization by electron-beam irradiation between 1 and 8 kGy was studied. An indirect chiral method based on the derivatization reaction of AA with o-phthaldialdehyde and N-acetyl-L-cysteine followed by reversed-phase HPLC and fluorimetric detection was applied to detect ten enantiomeric pairs of free AA (Asp, Ser, Thr, Ala, Tyr, Val, Trp, Phe and Leu). Five of the D-AA were not found in any of the samples analyzed; the other five remaining D-AA (D-Asp, D-Ser, D-Ala, D-Val and D-Leu) were detected both in irradiated and non-irradiated cooked ham samples, their content being in the range 1.25–13.79 μg/g. Although significant differences appeared for a few of the samples and doses, no positive correlation between the D-AA content and the irradiation doses was observed. Therefore, the electron-beam irradiation technique could be useful for sanitation of packed RTE cooked ham at doses allowed by WHO and EU, since it remains chemically safe to eat.     

全麦面条不同制作阶段挥发性风味物质比较分析

全麦熟面加工过程伴随着各种复杂的物理和化学反应,其挥发性风味物质在不同制作阶段香气特征尚不明确。本研究旨在揭示在熟面制作过程中气味物质的变化原因,为开发、改善、生产销售全麦鲜熟面提供指导。本研究采用气相色谱-离子迁移谱( GC-IMS) 联用技术,比较分析全麦粉、全麦生鲜面、全麦鲜熟面样品的挥发性组分。结果显示,共定性识别出55种挥发性风味物质,以醇类、醛类和酮类化合物为主。全麦粉制作成生面过程会加快全麦粉中脂质氧化或是氨基酸分解产生醛、醇、酯。煮制会使全麦面条中醛和醇的溶解和释放,并通过脂质氧化和热分解来调节酯和酮的浓度。以p＜0.05且VIP＞1为标准,共筛选出24种标志性差异化合物,这可能是造成全麦粉、全麦生面、全麦熟面风味差异的主要挥发性风味物质。     

超高压协同β-环糊精渗入对米饭回生的抑制

文中探究了超高压协同β-环糊精的渗入对方便米饭回生的影响。在粳米浸泡液中添加2%β-环糊精/羟丙基-β-环糊精,在60℃常压浸泡30 min,接着在40℃,500 MPa下浸泡20 min,最后蒸煮并焖饭制成米饭。通过差示扫描量热(DSC)、热重分析(TG)和X-射线衍射(XRD)研究新工艺对方便米饭在4℃贮存过程中的回生影响。新工艺米饭在4℃贮藏35d,其回生焓值比常压对照组降低了3.10 J/g,结晶度降低了7%。结果表明:新工艺显著延缓了米饭的回生进程,改善了米饭的贮存性。超高压协同添加β-环糊精的工艺为提高方便米饭食用品质提供了有效途径。