Effect of processing methods on product characteristics,lipid, fatty acid composition and oxidative stability of smoke-dried beef

Smoke-dried beef was pre-processed with water or by pressure cooking, weight losses were 50 and 54% respectively, with the rate of drying faster in the latter. There was a greater loss of total lipid and triglycerides in pressure cooked samples but the reverse was true for the phospholipids. The proportions of saturated and monoenoic fatty acids were slightly higher in the water cooked products although total unsaturation was slightly lower, the values being 37 and 39%, respectively. The fatty acid composition of the phospholipids was similar for both treatments except that the levels of polyenoic fatty acids were 16.4 and 14.43%, respectively in water and pressure cooked samples. Of the polyenes C20:4 accounted for about 75% of the fatty acids in the water cooked samples, compared with 40% with pressure cooking. After 60 weeks of storage at room temperature, pressure cooked samples were found to be more stable oxidatively: malonaldehyde was the principal oxidative by-product in both treatments.     

静态顶空与固相微萃取法分析婴幼儿辅食营养包中哈喇味的主要成分

为研究婴幼儿辅食营养包中哈喇味的主要成分,采用静态顶空与顶空固相微萃取技术提取婴幼儿辅食营养包中的气味成分,通过气相色谱-质谱联用技术进行定性分析,对两种方法所得的气味成分进行比较分析。结果表明:加速氧化实验后,样品中醛类含量变化最明显,两种检测方法中严重组和中度组挥发性成分都以醛类化合物为主。推测己醛、2-戊基呋喃、（E,E）-2,4-壬二烯醛、（Z）-14-甲基-8-十六碳烯-1-缩醛可能是婴幼儿辅食营养包中产生哈喇味的主要因素,而哈喇味可能是由其中几种物质相互作用而产生的。      

速溶豆浆晶的研制

本文主要介绍“速溶豆浆晶”生产的基本原理、生产工艺及质量分析,给出了各工序的主要工艺参数,阐述了脱除豆腥味和保持产品速溶性的一些问题。     

Identification of the influential odorants for the unpleasant rancid smell of ripe noni fruit (Morinda citrifolia)

In this study, the volatile changes of noni fruit in various ripening stages were analysed using gas chromatography–mass spectrometry. Eleven of the 35 identified volatiles were found odour-active through gas chromatography–olfactometry. Based on the aroma extract dilution analysis, hexanoic acid, octanoic acid and their methyl esters were considered as the key odorants for the smell of noni fruit. Results also indicated that the sensory perception of the rancid smell was resulted from the antagonistic effects of the key acid and methyl ester odorants. This study may facilitate the improvement of the acceptability of noni processed foods in the future.     

Sensory evaluation of the odour of a sunflower oil emulsion throughout oxidation

Oxidation of unsaturated fatty acids is responsible for off‐flavours, often described as rancid flavours. This study was aimed at describing the evolution of the odour of a sunflower oil‐in‐water emulsion during oxidation at 50 °C in the dark. Appearance of an odour and occurrence of oxidation were first tested for at short‐time aging (0–4 h) by the triangle test and measurements of oxygen consumption, respectively. The odour of the emulsion oxidised for up to 240 h was then characterised by sensory profile, while volatiles issued from lipid oxidation were analysed in the headspace by SPME. From 1 h of aging, while oxygen consumption remained weak, a significant change of the odour was detected by the panel. Up to 21 volatile compounds were identified in the headspace of long‐time‐oxidised emulsions. Beyond the rancid attribute, seven attributes were chosen to describe the odour of oxidised emulsions, four of which referring to solutions of a single volatile oxidation compound. The contribution of the fresh oil attribute, initially dominant, was progressively overtaken from 6 to 24 h of aging by the deep‐fried attribute, which later declined in favour of the painty attribute, predominant after 100 h. Evolution of intensity scores and contribution to odour profiles of attributes could not be easily related to one reference volatile compound or another, confirming the complex relationship between the generated volatile compounds and the perceived odour.     

Effect on lamb meat quality of including thyme (Thymus zygis ssp. gracilis) leaves in ewes’ diet

The aim of this study was to investigate the effect of including thyme leaves (TL) in the diet of pregnant sheep on the sensorial characteristics, bacterial spoilage and oxidative stability of lamb meat stored in modified atmosphere (70% O₂:30% CO₂). For this, thirty-six sheep were randomly assigned to three groups: control (basal diet), T₁ (3.7% thyme leaves), T₂ (7.5% thyme leaves). Meat spoilage (TV, PSY, MY, ENT, and LA), TBARS, CIELAB coordinates, metmyoglobin and the sensory characteristics of fresh lamb meat were analyzed on days 0, 7, 14 and 21. The presence of antioxidant compounds in the diet containing TL delayed (P < 0.05) colour deterioration, lipid oxidation and bacterial counts, while at the same time imparting a better appearance to the fresh lamb meat. In general, this effect was more pronounced at the higher level of TL (7.5%). High Pearson’s correlation coefficients were found between the sensory attributes, CIELAB coordinates and TBARS.     

Lipid Oxidations in Ordinary and Dark Muscles of Fish: Influences on Rancid Off-odor Development and Color Darkening of Yellowtail Flesh During Ice Storage

We investigated the role of lipid oxidation in the development of a rancid off‐odor in the early stage of ice storage in both ordinary and dark muscles of cultured yellowtail (Seriola quinqueradiata). The total lipid hydroperoxide content and thiobarbituric acid‐reactive substances (TBARS) of the dark muscle were significantly higher (P < 0.01) than those of the ordinary muscle during 2 d of ice storage. The increase in the metmyoglobin content of the dark muscle was accompanied by gradual darkening of the muscle color during ice storage. To distinguish the changes in odor characteristics of the muscles, sensory evaluation was carried out. Slight changes in the intensity of 7 different odors were noted in the ordinary muscles, and there was a significant increase in the overall, fishy, spoiled, and rancid smells of the dark muscle during 2 d of ice storage. No correlation was found between the total content of lipid hydroperoxide and the odor intensities in ordinary muscle; however, there was a significant correlation between the total lipid hydroperoxide content and rancid off‐odor and overall smell intensities in the dark muscle. The rate of lipid oxidation of the yellowtail dark muscle was significantly faster than that of the ordinary muscle. Lipid oxidation of the dark muscle was closely related to meat darkening and development of the rancid off‐odor during the early stage of ice storage.     

Effect of muscle type and cooking temperature on liver‐like off‐flavour of five beef chuck muscles

Steaks (1.9 cm thick) from the US Department of Agriculture (USDA) Select grade beef chuck muscles (Infraspinatus, Longissimus dorsi, Serratus ventralis, Supraspinatus and Terres major) were cooked to two temperatures commonly applied in US restaurants (71 °C and 82 °C) and evaluated for liver‐like off‐flavour by trained panel. Pigment content of raw muscles were determined to establish its effect on liver‐like off‐flavour. Mean myoglobin content of Serratus (9.26 mg g^?1) was significantly lower than other beef chuck muscles analysed in this study. Infraspinatus had highest (P < 0.05) mean liver flavour of 2.08 where other muscles had <2. Rancid flavour was slightly but significantly increased from 1.34 to 1.58 as internal cook temperature increased from 71 °C to 82 °C; however mean thiobarbituric acid (TBA) values were not affected by cooking temperature. Infraspinatus had small but significant incidence of liver‐like off‐flavour. Cooking temperature had a clear impact on rancidity as evaluated by trained panel but no direct impact on liver‐like off flavour was observed.     

Physicochemical characteristics and shelf life estimation of maize/soybean extrudates added with bovine haemoglobin

Maize/soybean (88:12) extrudates fortified with bovine haemoglobin as a source of iron with the addition of iron absorption enhancers were developed. The aims were to evaluate physicochemical characteristics and to predict shelf life by sensory analysis. Extrudates were made using a Brabender 20 DN single‐screw extruder. Specific mechanical energy consumption (SMEC), expansion ratio, specific volume, water solubility and water absorption were measured. Extrudates were stored at three temperatures (12.5, 30 and 45 °C) for 50 days. Colour, crispness and rancid flavour were evaluated by a trained panel. Both addition of haemoglobin and enhancers did not produce significant differences for SMEC, expansion and specific volume. Flavour was the attribute with the greatest degree of damage during storage, thus was used for predicting shelf life. The expanded product added with haemoglobin, and Na₂EDTA could be kept for 15 months at 15 °C or 10 months at 22 °C without rancid flavour development.     

固相微萃取-气质联用技术分析湖南腊肉中哈喇味的主要成分

采用固相微萃取-气相色谱质谱法对湖南腊肉产生的哈喇味进行成分分析。结果表明,3-辛烯-2-酮、反-2-辛醛、2-十三烯醛、2,4-葵二烯醛是腊肉哈喇味的主要成分,它们中的一种或者几种共同作用产生了哈喇异味。