Kefir粒发酵过程中牛乳体系的品质变化

为明确开菲尔粒(Kefir grains)在发酵过程中对牛乳体系品质变化的影响。本文将Kefir粒作为发酵剂应用于牛乳体系中,研究接种量、发酵时间和发酵温度对牛乳酸度、主要风味成分和流变性质的影响。结果表明,接种量、发酵温度、发酵时间对Kefir粒发酵作用的影响复杂。分析酸度变化的规律可知,相同条件下,接种量越大,酸度越高;电子鼻测定发酵乳中主要风味物质的变化发现,发酵温度越高,Kefir粒中的乳酸菌和酵母生长越快,产生风味物质的时间越短,但是菌种过快生长会导致发酵乳风味变差;流变仪测定发酵乳黏弹性、流动常数的变化可知,Kefir发酵乳的复合黏度随角频率增大而减小,储能模量G'和损耗模量G″随温度上升而增大,G'始终大于G″,tanδ始终小于1,体系呈现弹性特征。综合考虑实验结果和成本,选用在30℃条件下,接种量为0.40%的Kefir粒发酵48 h得到的酸度为86 °T,最终产品性质较为稳定,感官品质较为优良,这对Kefir发酵乳的工业化生产具有一定的指导意义。     

紫外线照射处理对馒头品质及保质期影响研究

目的研究紫外线照射处理的方法对馒头品质及保质期的影响。方法通过对馒头进行感官评价确定馒头的品质,通过测定馒头表面的微生物数量确定馒头的保质期。结果紫外线照射时间和紫外照射灯管数能够明显延长馒头的保质期。在紫外线照射时间7 s,紫外灯管数3根,紫外照射距离为5 cm时,微生物生长受到明显抑制,馒头的保质时间从20 h延长至40 h,而且对馒头的感官评价基本没有影响,具有良好的安全性。结论紫外线照射处理对馒头的品质影响较小,但能够明显延长馒头的保质期。     

短波紫外线结合发光二极管红光辐照对香椿保鲜效果的影响

目的 比较短波紫外线(ultraviolet C, UV-C)与发光二极管(light-emitting diode, LED)红光复合辐照和单一LED红光辐照对贮藏期香椿采后保鲜效果的影响。方法 将挑选后的香椿分为3组,在4℃下贮藏,通过测定感官指标、失重率、色差值、可溶性固形物含量、维生素C (vitamin C, VC)含量、还原糖含量、菌落总数、丙二醛(malondialdehyde, MDA)含量、1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl, DPPH)自由基清除能力、过氧化物酶(peroxidase, POD)和多酚氧化酶(polyphenol oxidase, PPO)活性指标比较不同处理的差异。结果 将红光复合辐照与单一LED红光辐照的处理效果比较后发现:在外观品质方面,前者显著地提高香椿的感官品质,其感官品质评分比对照高9.6分;有效地降低香椿的失重率,其失重率仅为对照的52.5%;在营养品质上,前者可以保持更高的可溶性固形物、VC和还原糖含量,其VC含量是对照的11.1倍;前者不仅有效地抑制香椿叶片中微生物的生长,还显...     

紫外LED冷光降解黄曲霉毒素B1技术对花生油品质影响的研究

目的考察紫外LED冷光降解黄曲霉毒素B_1(AFB_1)对花生油品质的影响。方法通过测定紫外LED冷光照射前后脂肪酸、酸价、过氧化值的变化来初步评价对花生油脂肪酸的影响。结果经紫外LED冷光技术处理的花生油,其脂肪酸组成及含量变化,酸价和过氧化值的变化均无显著性差异(P0.05),对花生油的品质影响不大。结论黄曲霉毒素降解机(紫外LED冷光技术)基本对花生油品质无影响,为花生油加工企业的实际生产提供一定的参考。     

Influence of sonication and high hydrostatic pressure on the quality of carrot juice

The combined effects of ultrasound (US) and high hydrostatic pressure (HHP) on enzymes, micro‐organisms, colouring pigments, total polyphenols, ascorbic acid and physicochemical properties of carrot juice were investigated. Carrot juice was treated with sonication (20 kHz, 70% amplitude) and HHP (250, 350, 450 MPa) at room temperature for 10 min. For comparison, fresh carrots were water blanched (WB) at 100 °C for 4 min and carrot juice was then extracted. As results, highest improvements in colouring pigments were observed in WB and US‐HHP450 treatments, which also completely inactivated micro‐organisms. The highest reduction in enzymes was observed in WB treatment followed by US‐HHP450. Total polyphenol contents increased significantly in US, HHP and US‐HHP treatments with the highest increase in US‐HHP450, but it decreased significantly in WB treatment. Ascorbic acid contents significantly decreased in WB and HHP450, while increased in US and US‐HHP treatments. Results indicate that US‐HHP450 treatment improves the quality of carrot juice and serves as a good alternative for blanching treatment.     

超声波处理对豌豆淀粉糊化、流变及质构特性的影响

以豌豆淀粉为原料,分别用0,150,300,450 W的超声波进行处理,考察超声波处理对豌豆淀粉糊化、流变及质构特性的影响。结果表明:超声波处理对豌豆淀粉的糊化、流变及质构特性都有较大影响。随着超声波功率的增加,豌豆淀粉糊峰值黏度、终值黏度、崩解值及回升值都显著下降,使豌豆淀粉冷稳定性及热稳定性得到提升;稠度系数k减小,流体指数n增大,触变性减小,流动性增加,使豌豆淀粉流变稳定性提高;G′与G″减小,tanδ增大,使豌豆淀粉黏弹性降低。此外,超声作用使豌豆淀粉凝胶的硬度、弹性、内聚性、胶着性及咀嚼性都呈下降趋势,其中硬度与胶着性下降最显著。扫描电镜表明,超声波对豌豆淀粉产生破坏作用,使淀粉颗粒表面出现坑洞及皱褶,部分颗粒结构变得不完整。     

紫外线照射与柠檬酸处理对鲜切苹果的保鲜作用

目的研究柠檬酸、紫外线照射、柠檬酸和紫外线照射联合处理对鲜切苹果生理生化的影响。方法以富士苹果为实验材料,分成4组,分别是0.5%柠檬酸(CA)溶液中浸泡5 min、紫外照射(UV)5 min/面、0.5%柠檬酸溶液中浸泡5 min+紫外照射(CA+UV)5 min/面、不处理的对照组(KB)。分别于0、1、3、5、7、10、13、15 d测定鲜切苹果的色差、多酚氧化酶(PPO)、过氧化物酶(POD)、苯丙氨酸解氨酶(PAL)活性。结果富士苹果经过切分后,褐变严重。PPO、POD活性升高,PAL活性变化曲折,总体呈上升趋势。柠檬酸、紫外、柠檬酸和紫外联合处理的3三种处理方式都可以抑制鲜切苹果的褐变,降低PPO、POD、PAL的活性。在4种处理方法比较中,柠檬酸和紫外联合处理的效果比较好。结论柠檬酸和紫外联合处理是鲜切苹果的理想的保鲜方法。     

Effect of ultraviolet and far infrared radiation on microbial decontamination and quality of cumin seeds

Abstract: Cumin seeds might be exposed to a high level of natural bacterial contamination, and this could potentially create a public health risk besides leading to problems in exportation. Ultraviolet (UVC) and far infrared (FIR) radiation has low penetration power, and due to that, there might be no detrimental defects to the products during a possible decontamination process. Therefore, the objective of this study was to determine the effect of UVC and FIR treatment on microbial decontamination and quality of cumin seeds. For this purpose, FIR treatment at different exposure times and temperatures were applied followed by constant UVC treatment with an intensity of 10.5 mW/cm² for 2 h. Total mesophilic aerobic bacteria of the cumin seeds were decreased to the target level of 10⁴ CFU/g after 1.57, 2.8, and 4.8 min FIR treatment at 300, 250, and 200 °C, respectively, following a 2 h UVC treatment. Under the given conditions, a complete elimination for total yeast and molds were obtained while there were no significant changes in volatile oil content and color of the cumin seeds. Consequently, combined UVC and FIR treatment was determined to be a promising method for decontamination of the cumin seeds. Practical Application: This research attempts to apply UVC and far infrared (FIR) radiation for pasteurization of cumin seeds. The data suggested that combined UVC and FIR radiation treatments can become a promising new method for pasteurization of cumin seeds without causing any detrimental defect to the quality parameters. The results of this industry partnered (Kadioglu Baharat, Mersin, Turkey— http://www.kadioglubaharat.com ) study were already applied in industrial scale production lines.     

Effects of isomalt on the quality of wheat flour dough and spicy wheat gluten sticks

The effects of different isomalt concentrations on the quality of wheat flour dough and spicy wheat gluten sticks (SWGS) were evaluated at the physical, structural and molecular levels. The results showed that the radial expansion rate (RER) and oil absorption rate (OAR) of SWGS increased first and then decreased with increased isomalt supplementation, which reached the maximum at 3 wt%. The pasting properties of wheat starch also changed, and the peak viscosity, breakdown and setback were decreased with the addition of isomalt. Dynamic rheological properties results showed that the storage modulus (G') and loss modulus (G'') increased with the addition of isomalt, which may be attributed to the reinforcement of gluten network structure by hydrogen bonding of isomalt. Scanning electron microscopy (SEM) images illustrated that the SWGS surface becomes smooth and the broken gluten structure was reduced after the addition of different isomalt levels compared with the control group. Overall, the wheat flour dough quality analysis showed that the addition of isomalt could generate a close binding with wheat starch and protein and further strengthen the internal structure of gluten through isomalt hydrogen bonds.     

Effects of ultraviolet irradiation on chemical and sensory properties of goat milk

Sensory and chemical consequences of treating goat milk using an UV fluid processor were assessed. Milk was exposed to UV for a cumulative exposure time of 18 s and targeted UV dose of 15.8 ± 1.6 mJ/cm². A triangle test revealed differences between the odor of raw milk and UV irradiated milk. Oxidation and hydrolytic rancidity was measured by thiobarbituric acid reactive substances and acid degree values (ADV). As UV dose increased, there was an increase in thiobarbituric acid reactive substance values and ADV of the milk samples. A separate set of samples were processed using the fluid processor but with no UV exposure to see if lipase activity and agitation from pumping contributed to the differences in odor. The ADV increased at the same rate as samples exposed to UV; however, sensory studies indicated that the increase of free fatty acids was not enough to cause detectable differences in the odor of milk. Solid phase microextraction and gas chromatography were utilized for the analysis of volatile compounds as a result of UV exposure. There was an increase in the concentration of pentanal, hexanal, and heptanal (relative to raw goat milk) after as little as 1.3 mJ/cm² UV dose. Ultraviolet irradiation at the wavelength 254 nm produced changes in the sensory and chemical properties of fluid goat milk.     

辐射处理对杜仲籽油氧化稳定性影响初探

本实验研究了微波、超声波和紫外线等三种辐射对杜仲籽油氧化稳定性的影响。结果表明：微波、超声波、紫外线三种辐射处理均会加速杜仲籽油的氧化。在处理初期,随着辐射时间的延长、强度的增大及温度的升高,杜仲籽油过氧化值不断增大;但在辐射处理后期,随着各处理条件的增强,由于碳键断裂、产生各种醛酮等低分子二级产物,使杜仲籽油的过氧化值呈现降低的趋势。表明各种辐射处理都会导致不饱和脂肪酸的氧化,应适当运用。而且过氧化程度的评价不能单纯根据过氧化值判断。     

辐照和巴氏杀菌对番茄果浆品质及微生物生长情况的影响

为了探索辐照剂量和巴氏杀菌对番茄果浆的品质和杀菌效果的影响,对番茄果浆进行1、2、3kGy的辐照和巴氏杀菌处理,分别考察处理后的番茄果浆在25℃下的总酸、总糖、pH、花青素、VC含量及大肠菌群数、菌落总数和霉菌总数的变化情况,由此得到最适宜的处理方式.结果表明:辐照处理和巴氏杀菌处理对番茄果浆均起到了较好的杀菌效果,且...     

Evaluation of the effects of ultraviolet light on bacterial contaminants inoculated into whole milk and colostrum,and on colostrum immunoglobulin G

Raw milk and colostrum can harbor dangerous microorganisms that can pose serious health risks for animals and humans. According to the USDA, more than 58% of calves in the United States are fed unpasteurized milk. The aim of this study was to evaluate the effect of UV light on reduction of bacteria in milk and colostrum, and on colostrum IgG. A pilot-scale UV light continuous (UVC) flow-through unit (45 J/cm²) was used to treat milk and colostrum. Colostrum and sterile whole milk were inoculated with Listeria innocua, Mycobacterium smegmatis, Salmonella serovar Typhimurium, Escherichia coli, Staphylococcus aureus, Streptococcus agalactiae, and Acinetobacter baumannii before being treated with UVC. During UVC treatment, samples were collected at 5 time points and bacteria were enumerated using selective media. The effect of UVC on IgG was evaluated using raw colostrum from a nearby dairy farm without the addition of bacteria. For each colostrum batch, samples were collected at several different time points and IgG was measured using ELISA. The UVC treatment of milk resulted in a significant final count (log cfu/mL) reduction of Listeria monocytogenes (3.2 ± 0.3 log cfu/mL reduction), Salmonella spp. (3.7 ± 0.2 log cfu/mL reduction), Escherichia coli (2.8 ± 0.2 log cfu/mL reduction), Staph. aureus (3.4 ± 0.3 log cfu/mL reduction), Streptococcus spp. (3.4 ± 0.4 log cfu/mL reduction), and A. baumannii (2.8 ± 0.2 log cfu/mL reduction). The UVC treatment of milk did not result in a significant final count (log cfu/mL) reduction for M. smegmatis (1.8 ± 0.5 log cfu/mL reduction). The UVC treatment of colostrum was significantly associated with a final reduction of bacterial count (log cfu/mL) of Listeria spp. (1.4 ± 0.3 log cfu/mL reduction), Salmonella spp. (1.0 ± 0.2 log cfu/mL reduction), and Acinetobacter spp. (1.1 ± 0.3 log cfu/mL reduction), but not of E. coli (0.5 ± 0.3 log cfu/mL reduction), Strep. agalactiae (0.8 ± 0.2 log cfu/mL reduction), and Staph. aureus (0.4 ± 0.2 log cfu/mL reduction). The UVC treatment of colostrum significantly decreased the IgG concentration, with an observed final mean IgG reduction of approximately 50%. Development of new methods to reduce bacterial contaminants in colostrum must take into consideration the barriers imposed by its opacity and organic components, and account for the incidental damage to IgG caused by manipulating colostrum.     

低聚糖类益生元对炼乳品质的影响

目的 为实现炼乳的减糖,研究不同低聚糖类益生元替代蔗糖对炼乳品质的影响。方法 选用低聚果糖、低聚异麦芽糖、低聚木糖、低聚半乳糖四种低聚糖类益生元分别作为蔗糖替代物,研究不同替代比的益生元炼乳体系质构、流变、感官、色泽、晶体大小的变化,得到最佳糖替代益生元及替代比例。结果 综合考虑质构、色泽、晶体大小、喜好度排序感官四种指标表明,低聚果糖炼乳和低聚异麦芽糖炼乳品质较为优良,其中低聚果糖炼乳可接受的替代比为15%以内、低聚异麦芽糖炼乳可接受的替代比为25%以内。进一步通过静态流变学试验表明低聚异麦芽糖是最佳糖替代物质,在炼乳体系中其最佳替代比为15%。结论 糖替代比15%的低聚异麦芽糖炼乳既满足了甜感需求,又实现了减糖的目标,此外益生元的加入赋予了炼乳更多的功能性。该研究可为炼乳产品的减糖开发提供一定的理论依据和技术支持。     

食盐对烩面面团品质和面筋网络结构的影响

采用低磁场核磁共振和激光共聚焦扫描显微镜,研究了食盐添加量(0~5%)对烩面面团水分分布状态和面筋网络微观结构变化的影响,并结合面团拉伸特性、动态流变学特性以及麦谷蛋白大聚体含量变化对各项试验指标进行综合分析。结果表明:添加食盐可以提高面团的弹性模量G′和黏性模量G″;食盐添加量在0%~3%范围内,结合水和半结合水比例变化不显著,自由水比例降低,食盐添加量超过3%,结合水和自由水比例降低,半结合水比例上升;随着食盐添加量的增加,面筋网络微观结构变的越来越紧密,面团的最大拉伸力逐渐升高;在0%~5%范围内,面团中麦谷蛋白大聚体含量升高,湿面筋指数上升,添加量超过3%,面团中湿面筋含量下降,面团的拉伸距离下降,麦谷蛋白大聚体含量变化不显著。综合考虑,3%以下添加量可以获得理想的烩面面团品质。     

Effects of addition of different vegetable oils to lactating dairy ewes' diet on meat quality characteristics of suckling lambs reared on the ewes' milk

The effect of different vegetable oils used in the diet of lactating ewes on the meat quality of their suckling lambs has been evaluated. Lambs (males and females) were slaughtered at 11 kg. Fortyeight lactating Churra ewes (prolificacy 1.5) and their suckling lambs were assigned to four treatments according to the oil added (3% on weight basis) to the ewes' daily ration: palm oil as control (CON); olive oil (OLI); soybean oil (SOY); and linseed oil (LIN). Analyses of pH, colour, thiobarbituric acid reactive substances (TBARS), tocopherol levels, volatile compounds and a sensory evaluation were carried out on suckling lambs' meat. Results showed no substantial effect on pH, colour, TBARS and tocopherol levels. Volatiles typically derived from lipid oxidation were higher in SOY group. However, panellists were only able to correctly identify samples from LIN group. Furthermore, the meat from LIN group showed lower scores towards odour and flavour quality and overall liking than that from the rest of treatments.     

高场强超声对蛋清液起泡特性的影响

为改善蛋清液的起泡性,采用不同超声功率(120,240 W)和超声时间(1,5,10,20,30 min)的高场强超声(20 kHz)对蛋清蛋白进行改性.结果表明,在功率120 W下超声处理20 min,蛋清蛋白的起泡性最佳(266.7％),是未处理蛋清的6.9倍.超声处理显著降低了蛋清液的表观黏度、表面张力和粒径大小...     

紫外辐照法提高咸蛋清起泡性的工艺研究

咸蛋清是蛋制品的副产物,一直以来仅有少部分用于饲料,大部分被丢弃,造成了较大的环境污染和资源浪费。本实验以经超滤脱盐的咸蛋清为原料,利用紫外辐照法,研究了辐照时间、pH、温度对咸蛋清起泡力的影响。利用响应面分析法确定了最佳工艺参数为辐照时间32min,pH5.0,温度30℃。此时的咸蛋清粉的起泡力为65.33%。      

小麦粉流变学特性品质指标间的关系研究

采用粉质仪、拉伸仪、吹泡仪和面筋仪分别对56种具有代表性的小麦粉样品进行检测,研究小麦粉的粉质特性、拉伸特性、吹泡特性和面筋特性等流变学品质指标间的关系。结果表明:粉质特性、拉伸特性、吹泡特性和面筋特性有些指标之间存在显著或极显著相关关系,有些指标各自具有特异性。小麦和面粉进行品质检测时,应根据其检测目的和食品用途选择使用合适的指标进行评价,提高研究和检测效率。     

Effects of wax coatings and postharvest storage on sensory quality and aroma volatile composition of ‘Mor’ mandarins

BACKGROUND: Mandarins suffer from accumulation of off‐flavours after harvest. In this study the sensory quality and aroma profile composition of homogenised segments of untreated (control) and wax‐coated ‘Mor’ mandarins after 7 days at 20 °C or 3 or 6 weeks of cold storage at 5 °C were examined. RESULTS: Fruit taste score decreased during storage and following wax coating, and this was attributed to decreases in sourness and mandarin flavour and accumulation of off‐flavours. Aroma profiling identified 31 volatiles that decreased by at least 50% during storage and after waxing and thus may be involved in the observed flavour loss. In contrast, 13 volatiles, mostly belonging to ethanol fermentation and fatty acid and amino acid catabolism pathways, significantly increased at least twofold and probably contributed to off‐flavour enhancement. CONCLUSION: The results showed that after harvest there was a progressive decrease in sensory quality of ‘Mor’ mandarins. It is proposed that observed decreases in contents of sesqui‐ and monoterpenes and short‐chain oxygenated fatty acids may contribute to the decrease in mandarin flavour, whereas increases in the contents of ethanol fermentation metabolites and derivates of fatty acid and amino acid catabolism are most likely involved in causing the enhanced sensation of off‐flavours. Copyright © 2010 Society of Chemical Industry