Effect of antioxidant (alpha-tocopherol and ascorbic acid) fortification on light-induced flavor of milk

The effectiveness of added antioxidants against oxidation off-flavor development in light-exposed milk was evaluated using sensory and chemical analysis. Sensory testing for similarity showed no perceivable difference between control milk and milk with added (1) 0.05% alpha-tocopherol (TOC) and (2) 0.025% alpha-tocopherol and 0.025% ascorbic acid (TOC/ASC), but did demonstrate a perceivable difference when adding (3) 0.05% ascorbic acid (ASC) alone. Subsequently, sensory testing for difference showed a significant difference in oxidation off-flavor between light-exposed control milk and light-exposed milk with added TOC/ASC, whereas milk fortified with TOC was not different from control. Gas chromatography-olfactometry showed that more aroma-active flavor compounds were observed in light-exposed milk treated with TOC and TOC/ASC than light-exposed milk with no added antioxidants. The thiobarbituric acid reactive substances (TBARS) test verified chemically the extent of oxidation in control and antioxidant-treated milk samples. Milk that was exposed to light for 10 h showed a significantly higher TBARS value (0.92 +/- 0.09 mg/kg) than milk that was protected from light (0.59 +/- 0.184 mg/kg), or milk that was treated with TOC/ASC (0.26 +/- 0.092 mg/kg). Direct addition of low levels of antioxidants (TOC/ASC) to milk protected its flavor over 10 h of light exposed storage.     

天然抗氧化剂抑制油脂氧化的研究进展

油脂氧化是食品工业中经常遇到、严重影响食品品质的主要问题之一.虽然应用各类人工合成抗氧化剂在抑制食品中脂肪氧化的问题上取得了比较好的效果,但是这一类抗氧化剂会带来食品安全问题.深入研究和推广应用天然抗氧化剂是同时解决脂肪氧化和食品安全问题的重要途径.     

Aroma Volatiles in Cooked Alligator Meat

Volatile components from cooked (convection oven at 176.7°C for 30 min) alligator meat were isolated by vacuum simultaneous distillation and solvent extraction (V-SDE) and dynamic headspace sampling (DHS) and analyzed by gas chromatography combined with mass spectrometry, Fourier transform infrared spectroscopy, or olfactometry. We identified 56 compounds in V-SDE extracts and 13 in DHS extracts. Volatile profiles were similar for all alligator meat samples regardless of alligator size (length). However, concentration of volatiles increased as alligator size increased. Most volatile compounds were lipid-derived aldehydes, which made up 73.9–79.4% of total volatiles in V-SDE extracts and 82.4–89.2% in DHS extracts. Hexanal, the most abundant compound, and (Z)-4-heptenal were considered responsible for the green, grassy and fishy, rancid off-odor of cooked alligator meat samples.     

Presence of synthetic antioxidants in organic and conventional milk

Samples of conventional (n = 11) and organic (n = 81) milk, both raw and heat-treated, were analysed for the presence of synthetic antioxidants (butylated hydroxytoluene, butylated hydroxyanisole, dodecyl gallate, propyl gallate and octyl gallate) to verify whether those labelled as “organic” corresponded to EU Regulations on the use of additives in such products. The analysis detected only the antioxidant BHT and its aldehyde BHT–CHO in all 11 conventional milk and in 18 of 81 organic milk samples. The investigation highlights the importance of strict control of organic dairy production, since synthetic antioxidants added to feedstuff to prevent rancidity can be transferred to milk.     

Lipid Oxidation and Warmed-Over Aroma in Cooked Ground Pork from Swine Fed Increasing Levels of Iron

Fifteen crossbred feeder pigs were fed to market weight on corn-soy rations containing either 62, 131, or 209 ppm iron. After slaughter, pork was ground, cooked, and stored at 4°C for 12 days. Heavily fortifying swine rations with iron (≥200 ppm) increased nonheme iron (NHI) and thiobarbituric acid reactive substances (TBARS) in cooked, stored ground pork (GP) but did not increase warmed-over aroma (WOA) (p>0.05). NHI, TBARS, and WOA increased during storage. TBARS strongly correlated with WOA during storage (r=0.903) and with NHI (r=0.901).     

Flavor and stability of pasteurized milk with elevated levels of conjugated linoleic acid and vaccenic acid

The objectives of this study were to determine if flavor differences between 2% fat pasteurized milks with and without naturally enhanced vaccenic acid (VA) and cis-9, trans-11 conjugated linoleic acids (CLA) levels could be detected over the commercial shelf life of the product and to determine if milk with elevated VA and cis-9, trans-11 CLA levels was more susceptible to development of light-induced oxidative flavor defects. Cows were fed a control diet or the same ration supplemented with 2% soybean oil and 1% fish oil (CLA diet). The milk, standardized to 2% fat, was pasteurized, homogenized, and stored in plastic containers at 4 degrees C. Oxidation was induced by exposing half of the containers to light. Testing was conducted at 1, 7, and 14 d postpasteurization. Average cis-9, trans-11 CLA content of the milks from the control and CLA diet groups was 0.52 and 4.74 g/100 g of fatty acids, respectively (8-fold increase). Average VA content of the milk from the control and CLA diet groups was 1.43 and 12.06 g/100 g of fatty acids, respectively (7.5-fold increase). Together, VA plus CLA represented almost 17% of the total milk fatty acids. There was no effect of light exposure on fatty acid composition initially or over the 14-d storage period. Although VA, cis-9, trans-11 CLA, and degree of unsaturation were significantly elevated in the milk from the CLA diet group, untrained panelists were unable to detect flavor differences initially or over time in 15 of 16 triangle test evaluations. Similarly, sensory results indicated no difference in susceptibility to the development of oxidized off-flavors between the milk from the control and CLA diet groups, even when oxidation was induced by light exposure.     

不同可见光照波段对无菌牛奶氧化感官的影响

研究不同可见光光照波段对无菌牛奶乳脂氧化感官的影响,确定对牛奶感官变化影响最大的光照波段。将牛奶试样分别放入透光对照组、蓝色滤光组(400～500nm)、绿色滤光组(500～600nm)、红色滤光组(600～700nm)和避光对照组中,定期测评试样的感官变化(色差、质地、气味和滋味)。结果表明,绿色滤光组条件下的试样感官变化最为显著,其次是蓝色滤光组的。     

乳及其制品中风味物质的研究进展

乳尤其是发酵乳中的风味物质种类繁多,包括非挥发性酸、挥发酸、羰基化合物以及蛋白、脂肪和乳糖等的分解物。由于加工过程中微生物和理化的原因,容易使乳制品产生不良风味。通过加入抗氧化剂等添加剂、加强杀菌措施、控制原料奶的品质和环境条件来控制风味的变化,提高其品质。     

A 100-Year Review: Sensory analysis of milk

Evaluation of the sensory characteristics of food products has been, and will continue to be, the ultimate method for evaluating product quality. Sensory quality is a parameter that can be evaluated only by humans and consists of a series of tests or tools that can be applied objectively or subjectively within the constructs of carefully selected testing procedures and parameters. Depending on the chosen test, evaluators are able to probe areas of interest that are intrinsic product attributes (e.g., flavor profiles and off-flavors) as well as extrinsic measures (e.g., market penetration and consumer perception). This review outlines the literature pertaining to relevant testing procedures and studies of the history of sensory analysis of fluid milk. In addition, evaluation methods outside of traditional sensory techniques and future outlooks on the subject of sensory analysis of fluid milk are explored and presented.     

奶香风味香肠生产加工工艺

介绍奶香风味香肠的基本配方和对生产加工工艺进行研究,奶香风味香肠具有自然浓郁的奶香、营养丰富、风味独特,产品使用方便,卫生安全。     

抗氧化剂对早餐肠高压后脂肪氧化的影响

为探究抗氧化剂对早餐肠高压后脂肪氧化的影响,在低温鸡肉早餐肠中添加0.05%的乙二胺四乙酸二钠(Na2EDTA)或维生素E(VE),与无添加抗氧化剂组作对比,然后进行不同强度的超高压处理(HPP,400、600MPa,20min),检测各组样品在4℃下贮藏28d各脂肪氧化指标的变化。结果表明:4℃随着贮藏时间延长,早餐肠的不饱和脂肪酸(UFA)比例逐渐减小,POV和TBA值逐渐增大。贮藏前期,脂肪氧化以一级氧化为主;后期二级氧化占主导作用。抗氧化剂Na2EDTA和VE都能在高压下提高脂肪的稳定性,且前者的抗氧化效果更佳。     

天然与合成食品抗氧化剂的发展

加工食品与新鲜食品的区别,在于前者除了主要的生产原料外,还可加入适当的配料或添加剂,如营养素、矿物质、甜味剂、酶制剂或其他各式各样的物质,以增加其营养价值,改进其组织结构,提高其感官素质,延长其保质期,甚至成为有治疗功效的保健食品。 我国幅员辽阔,资源丰富,并且有药食同源的传统,可利用的食品原料多不胜数。近年来,我国的食品工业发展一日千里,1997年的总产值已达7,000亿元人民币。在质量方面,国外先进设备的引入,先进管理手段的引用,都有助于提高我国加工食品的竞争能力。相信在不久的将来,我国的加工食品将在国际市场上取得更好的成绩。 为了迅速达到这个目标,食品工业同仁每天都努力不懈地在方方面面进行研究并作出改善。有鉴于此,本期特别推出食品配料专辑,介绍一些既特别而又具备功能特性的食品配料,以飨读者,也藉此为推动我国食品工业的发展献一份力。     

Oxidative stability of milk influenced by fatty acids, antioxidants, and copper derived from feed

Differences in the oxidative stability of milk from cows fed grass-clover silage or hay were examined in relation to fatty acid composition and contents of antioxidants and copper in the milk. The oxidation processes were induced by exposing the milk to fluorescent light. Protein oxidation was measured as an accumulation of dityrosine, whereas lipid oxidation was measured as an accumulation of lipid hydroperoxides as the primary oxidation product, and as the secondary oxidation products, pentanal, hexanal, and heptanal. No differences were found in the protein oxidation of the 2 types of milk measured as accumulation of dityrosine, but there was an increased accumulation of lipid hydroperoxides and hexanal in milk from cows fed grass-clover silage, compared with milk from cows fed hay. The higher degree of lipid oxidation in milk from cows fed grass-clover silage could not be explained from the concentration of α-tocopherol, carotenoids, uric acid, and copper in the milk. However, it was thought to be highly influenced by the significantly higher concentration of linolenic acid present in milk from cows fed grass-clover silage. A larger part of α-tocopherol and β-carotene was transferred from the feed to the milk when cows were fed grass-clover silage than when cows were fed hay as roughage. The significantly higher concentration of polyunsaturated fatty acids in milk from cows fed grass-clover silage may be important for the better transfer of α-tocopherol from the feed to the milk. Other circumstances, as the different conditions in the rumen may also play a role, due to the different types of roughages and their digestibility, or be related to the mechanisms during milk production for the higher yielding cows fed grass-clover silage.     

Identification of objectionable flavors in purported spontaneous oxidized flavor bovine milk

Spontaneous oxidized flavor (SOF) has been reported over the past 5 decades as a sporadic objectionable flavor problem in bovine milk. Parameters previously reported to influence SOF development in milk have been contradictory, limiting the ability to monitor and develop mitigation strategies. The current paper investigates the causative compounds associated with milk identified as SOF milk in the Midwest dairy region of the United States. Based on GC/MS-olfactometry analysis, endo-borneol, 2-methylisoborneol, and α-terpineol were identified as the off-flavor compounds. Sensory recombination studies further confirmed the sensory contribution of these compounds to the noted off-flavor attributes in the original milk, which were described as “green,” “musty,” and “unclean.” These compounds are known microbial-derived flavor taints, indicating oxidation was not the origin of the objectionable flavor in the milk. This noted misclassification of the milk as SOF indicates the challenge of defining flavor defects without the identification of the active compounds.     

脂质过氧化及抗氧化剂抗氧化活性检测方法

越来越多研究表明,很多疾病和衰老现象都与脂质过氧化有关。该文对近年脂质过氧化及抗氧化剂抗氧化活性检测方法作简单综述,包括气相色谱、液相色谱、质谱、化学发光法等,并对不同方法进行综合比较与评价。因各种检测技术对象各有不同,且各自各有优缺点,因此,要针对不同实验目的及条件以选择不同检测方法。     

Effectiveness of natural versus synthetic antioxidants in a rice bran oil-based structured lipid

Antioxidants were evaluated for their ability to improve oxidative stability index (OSI) of enzymatically prepared rice bran oil-based structured lipid (RBOSL) containing caprylic acid. RBOSL was purified by short-path distillation. Vitamin E concentration decreased significantly in RBOSL after enzymatic modification. Total γ-oryzanol concentration after modification was not significantly different. OSI of RBOSL containing rosemary extract (RE), carnosic acid (CA), tertiary butyl hydroquinone (TBHQ), ethylenediamine tetraacetic acid (EDTA), and α-tocopherol (TOC), and 50:50 (w/w) combinations in concentrations of 200, 300, 400 and 500 ppm were determined. The OSI of unmodified rice bran oil (RBO) was 12.4 ± 0.2 h and significantly higher than RBOSL which was 11.4 ± 0.0. Mean peroxide and p-anisidine values for antioxidant treatments in RBOSL with the highest OSI values were determined after incubation at 60 °C for 21 days and sampled every 3 days. Mean peroxide and p-anisidine values for CA and CA/RE were comparable to TBHQ.     

奶粉加速破坏性实验中质量参数的确定

在35℃和45℃的恒湿贮存条件下，考察了全脂和脱脂奶粉的脂肪氧化以及参与美拉德反应的蛋白质变性情况。全脂奶粉由于脂肪含量高，45℃下的硫代巴比妥酸反应物(TBARS)在10d以后便开始递增，明显早于30d才变化的反映美拉德反应的荧光强度，说明首先导致全脂奶粉品质变化的原因是脂肪氧化。在35℃和45℃下。脱脂奶粉荧光强度的增加都先于全脂奶粉，并且增加的幅度都很大，通过运用SDS-PAGE对蛋白质结构进行分析对照，荧光强度可以实时反映蛋白质的变性程度。     

巧克力风味牛奶的研制与开发

近年来市场上出现的巧克力牛奶一般都是用巧克力加牛奶直接配制而成的,由于巧克力热量高,易导致肥胖、高血脂等疾病,因此在市场上的销售受到了一定的限制。本课题通过选用巧克力香精替代巧克力,以鲜牛奶为主要原料,选用L9(33)正交表,通过正交实验筛选最佳配方。试验结果表明鲜牛奶85.0%,复合稳定剂0.16%,巧克力香精0.07%,食用色素0.106%,AK糖0.02%,可可粉0.4%,白砂糖2.0%。产品经分析检测符合国家质量卫生标准,口感细腻,巧克力风味浓郁,奶香突出,色泽诱人,是一种非常有发展前途的新型风味牛奶。