生料醋醅中巴氏醋杆菌的发酵条件优化及有机酸分析

以生料醋醅中筛选出的巴氏醋杆菌L3为发酵菌株,在初始乙酸量、初始乙醇量、醋酸菌接种量3个因素的单因素试验基础上,采用响应面法优化巴氏醋杆菌的发酵条件,并检测发酵液中的有机酸含量。结果表明:最佳发酵条件为初始乙酸量2%,初始乙醇量4.5%,醋酸菌接种量4%,此条件下总酸可达48.65g/L。利用高效液相色谱法检测发酵液中的有机酸,含量分别是草酸0.08g/L、乳酸2.80g/L、乙酸37.60g/L、柠檬酸0.17g/L,琥珀酸0.47g/L。分析得乙酸、乳酸产量最高,是醋中的主体酸,草酸、柠檬酸、琥珀酸主要起柔和口感的作用,不同种类的有机酸共同构成醋的风味特征。     

发酵条件对梨醋酿造过程中有机酸的影响

采用反相高效液相色谱分析了梨酒、梨醋中有机酸,研究了发酵条件对其有机酸的影响。研究结果表明:酿酒酵母在酒精发酵过程中可代谢梨汁中有机酸。与梨汁相比,梨酒中的草酸、奎宁酸含量下降,乳酸、琥珀酸含量上升。梨酒中乙酸、琥珀酸随着酒精发酵温度的升高而增加,而苹果酸、乳酸、奎宁酸则随着酒精发酵温度的升高而降低。醋酸菌具有代谢各种有机酸的功能,在醋酸发酵过程中均消耗柠檬酸,而产生和积累酒石酸。梨醋中酒石酸、奎宁酸、莽草酸、琥珀酸和乳酸随着醋酸发酵温度的升高而增加,苹果酸和草酸几乎不受发酵温度的影响。发酵方式影响醋酸菌对有机酸的代谢。     

枇杷醋生产中酒精发酵工艺优化及酸味特征分析

采用金华1号红肉枇杷为试验材料,对枇杷醋生产工艺中酒精发酵工艺参数进行优化,并分析醋基的酸味特征。研究酵母种类及接种量、发酵pH、发酵温度和初始糖度对枇杷醋醋基品质的影响,并以酒精度为响应值确定最优的发酵条件。结果表明,酵母菌种Yb为枇杷醋醋基酒精发酵优势酵母菌种,最优工艺参数为发酵温度25℃,酵母接种量0.05%、pH 3.5,该条件下枇杷醋醋基酒精度8.50%Vol,有机酸含量12.228g/L。枇杷醋醋基酸味特征主要由苹果酸、乳酸、乙酸和琥珀酸构成,占总有机酸的95.4%,构成枇杷醋醋基酸味感的94.7%。高含量酒精和适当含量的有机酸是后续醋酸发酵后醋酸含量的保证以及构成枇杷醋果酸味和一定功能作用的重要成分。     

木瓜酒和木瓜醋发酵工艺及其有机酸组成分析

以光皮木瓜为原料,发酵木瓜干酒,再通过液态深层发酵酿制木瓜醋,确定了木瓜干酒和木瓜醋的发酵工艺,并对木瓜酒和醋主要有机酸进行分析。光皮木瓜经榨汁、调整糖度后进入发酵工序,酒精发酵采用带皮渣半固态发酵方式,条件为加水比例1.5∶1（m/m）、初始糖度18%、果酒干酵母接种量0.1%、在24 ℃条件下发酵64 h,木瓜酒酒度（乙醇体积分数）为9.45%。醋酸发酵采用半连续式液态深层发酵法,调整初始酒度7%,醋酸菌接种量10%,在34 ℃条件下醋酸发酵80 h,木瓜醋总酸度为4.52%;分割留种发酵仅需24 h即可完成醋酸发酵。采用反相高效液相色谱法从木瓜干酒和木瓜醋中检出10 种有机酸,分别是草酸、酒石酸、甲酸、苹果酸、α-酮戊二酸、乳酸、醋酸、柠檬酸、富马酸和琥珀酸。实验确定的发酵工艺以及有机酸的分析与鉴定可为木瓜干酒及木瓜醋产品的开发提供理论依据。     

葡萄酒酿造过程中有机酸变化规律研究

采用离子色谱法分析了葡萄酒中9种有机酸含量。通过对赤霞珠葡萄酒发酵过程中主要有机酸变化分析,研究其从葡萄汁到原酒的酿造过程中有机酸含量变化规律和量变的幅度。结果表明,葡萄酒中有机酸主要有酒石酸、苹果酸、乳酸、柠檬酸和琥珀酸,葡萄汁经发酵产生了乳酸、乙酸和琥珀酸。酿造过程中酒石酸、苹果酸、抗坏血酸和柠檬酸含量一直呈下降趋势;草酸和琥珀酸含量先增高后减少,乳酸含量一直呈上升趋势。乙酸是葡萄酒酒精发酵的主要副产物,含量为0.2～0.3 g/L。     

荔枝果酒加工过程中有机酸的变化研究

该文研究了荔枝果酒在加工过程中有机酸的变化,结果表明,荔枝酒中主要的有机酸为乳酸、苹果酸、酒石酸、乙酸和琥珀酸.荔枝果酒的口感不佳,是由于苹果酸、乙酸、酒石酸及琥珀酸含量过高而引起.荔枝汁加工成荔枝酒的过程中,苹果酸、酒石酸及琥珀酸的含量分别增加2.80g/L～2.27g/L、0.77g/L和0.27g/L;乙酸含量减少9.44g/L～9.38g/L.要调整相关有机酸的含量和比例以达到改善荔枝酒口感的目的,可以通过控制酶解、调整成分及酒精发酵等工艺过程而实现.     

枇杷醋醋酸发酵工艺优化及醋酸味品质特征研究

以红肉枇杷为实验原料,对枇杷醋醋酸的发酵工艺进行优化并对醋酸味品质进行分析。通过单因素设计实验,研究发酵pH、发酵温度、醋酸菌接种量以及初始乙醇含量对醋酸味品质的影响,在此基础上进行4因素3水平的响应面优化试验。研究结果表明,发酵pH4.0,醋酸菌接种量为20%,初始乙醇体积分数为6%,发酵温度为30℃的条件下,枇杷醋的风味品质较优,并测得醋中总有机酸含量为53.213 g/L,其中乙酸占68.84%,是醋的主体酸;乙酸和其他有机酸(除草酸外)味觉强度分别为3 052.7和826.2,分别占比78.7%和21.3%。柠檬酸、乳酸和酒石酸在醋酸发酵中含量增加的同时缓冲了乙酸所带来的刺激性酸味,使得枇杷醋酸味更加柔和,它们共同构成了枇杷醋酸爽的风味特征。     

山葡萄酒发酵过程中营养成分变化的研究

以山葡萄"北国蓝"果实为试材,分析山葡萄酒发酵过程中各成分的变化及差异显著性。结果表明,在山葡萄酒酿造过程中,醪液中总糖含量持续下降并趋于稳定,可滴定酸含量持续下降;总糖含量在发酵前期差异极显著,后发酵阶段无差异,可滴定酸差异显著性则与之相反;总酚、单宁含量均呈先升高后降低的趋势,总酚、单宁在整个发酵过程存在差异,但差异不显著。有机酸总量在葡萄酒发酵过程中持续降低,降低了55.67%。酒石酸与苹果酸含量明显降低,分别降低了59.53%和62.50%;柠檬酸含量低于2.00 g/L,并无明显变化;乳酸、琥珀酸和乙酸均持续升高,草酸明显降低,这四种有机酸含量均低于0.30 g/L。有机酸总量、酒石酸和苹果酸均在发酵各时期差异极显著,乳酸差异显著,乙酸、草酸差异不显著,柠檬酸、琥珀酸无差异。     

基于RP-HPLC法测定水果及其果酒中有机酸含量

采用反相高效液相色谱法同时测定菠萝皮渣、火龙果汁及其发酵酒中草酸、柠檬酸、酒石酸、苹果酸、丙酮酸、琥珀酸、乳酸和乙酸8种有机酸组成和含量;色谱条件:色谱柱BP-OA,流动相A(1%H_3PO_4)和B(超纯水),柱温30℃,流速0.5 mL/min,紫外检测器(210 nm)。结果表明,各有机酸分离度在1.34以上,检出限为0.03~0.49μg/mL,RSD为0.9%~3.1%,平均回收率在93.4%~108.6%之间(S/N=3)。柠檬酸和苹果酸在菠萝皮渣中含量最高,而火龙果汁中苹果酸含量最高。其果酒中柠檬酸、苹果酸和草酸含量降低,但琥珀酸、丙酮酸、乙酸、酒石酸和乳酸含量升高。菠萝酒中柠檬酸、苹果酸和草酸含量分别降低96.04%,71.84%和77.20%,琥珀酸含量升高72.13%。火龙果酒与果汁相比苹果酸含量降低91.41%,草酸含量降低52.02%,而乙酸含量升高88.32%。     

泡豇豆发酵过程中有机酸变化及对亚硝酸盐降解的影响

为了探究泡菜发酵过程中有机酸变化规律,以豇豆为原料自然发酵制作泡菜。采用高效液相色谱法(HPLC)对泡豇豆在发酵过程中蔬菜组织和发酵液中的有机酸种类及含量进行分析测定,并对各有机酸降解亚硝酸盐的能力进行比较。结果表明,蔬菜组织和发酵液中含有8种有机酸,分别为草酸、酒石酸、苹果酸、乳酸、乙酸、柠檬酸、富马酸和琥珀酸;各有机酸变化趋势有所不同,发酵7 d后,蔬菜组织中柠檬酸含量最高,为641. 59 mg/(100 g),发酵液中苹果酸含量最高,为195. 39 mg/(100 g);各有机酸降解亚硝酸盐能力大小顺序依次为草酸、酒石酸、苹果酸、柠檬酸、琥珀酸、乙酸、乳酸、富马酸。此研究为阐明泡菜中亚硝酸盐降解机理提供了理论基础。     

Prevention of the deterioration of polyphenol-rich beverages

Only a small amount of H₂O₂ was detected in beverages, such as tea or coffee, immediately after opening caps of bottles, but H₂O₂ was gradually produced in the beverages after opening the caps, i.e. exposure to air. The beverages with high concentrations of polyphenols showed high 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activities, but produced relatively high concentrations of H₂O₂ when they were exposed to air, possibly due to oxygen. The production of H₂O₂ increased both with duration of the exposure to air and rise in temperature. Since H₂O₂ is toxic, ways to prevent the deterioration of catechin-enriched green tea, i.e. H₂O₂ production, were studied. The addition of catalase, which is an enzyme decomposing H₂O₂, reduced the H₂O₂ concentration, but it was inactivated at a high temperature. The addition of l-cysteine or glutathione (reduced form), with a thiol residue, reduced the H₂O₂ concentration. Addition of citric acid, malic acid, succinic acid, fumaric acid, l-ascorbic acid, l-glutamic acid and l-aspartic acid also reduced it, possibly because they lower the pH of the tea.     

Comparison of Properties of New Sources of Partially Purified Inulin to Those of Commercially Pure Chicory Inulin

Newly developed inulin powders were prepared from roots of Asparagus falcatus (AF) and Taraxacum javanicum (TJ) plants grown in Sri Lanka. Inulin content, analyzed by enzymatic spectrophotometric as well as high‐performance liquid chromatographic methods, showed that AF and TJ inulin powders contain 65.5% and 45.4% (dry wt) inulin, respectively, compared with 72% dry wt in the commercially available chicory inulin. Treating the AF and TJ inulin powders using ion exchange techniques significantly (P < 0.05) reduced their contents of micro (Zn, Cu, Mn, Fe) and macro (Na, K, Ca, Mg) elements. Enzymatic hydrolysis of inulin into fructose and glucose by fructanase, and FT‐IR analyses proved that the developed AF and TJ inulins have characteristic molecular composition similar to commercial inulin. TJ inulin contained significantly (P < 0.05) greater amounts of total phenolics (4.37 mg GAE/g), total flavonoids (2.79 mg QE/g), and antioxidant capacity (833.11 mM TE/g) than AF inulin, which contained 1.33 mg GAE/g of total phenolics, 0.43 mg QE/g of total flavonoids, and 406.26 mM TE/g antioxidant capacity. The current study suggests that the newly developed inulin from AF and TJ roots could be used as an alternative commercial source of inulin for the food industry.     

Influence of type of muscles on nutritional value of foal meat

The effect of type of muscle on nutritional characteristic (fatty acid profile, amino acid content, cholesterol and major and minor mineral) of foal meat was investigated. Six muscles: longissimus dorsi (LD), semimembranosus (SM), semitendinosus (ST), biceps femoris (BF), triceps brachii (TB) and psoas major & minor (PM) from twelve foals slaughtered at 15 months from an extensive production system in freedom regimen were extracted for this study. Horse meat is characterized by low fat, low cholesterol content, rich in iron and in vitamin B. Statistical analysis showed that the cholesterol content did not show significant differences (P > 0.05) among muscle with mean value range between 0.62 and 0.57 mg/100 g. Most fatty acid presented significant differences (P < 0.05) with respect to the type of muscle. The obtained results showed that except for the polyunsaturated linoleic acid, the highest contents of fatty acids were found in the hindquarter muscles. Regarding amino acid profile, significant differences (P < 0.05) were observed among muscles and our results indicated that, 100 g of foal meat covered from 80.6 to 86.7% for the daily requirement for an adult man weighing 70 kg for essential amino acids for ST and LD muscles, respectively. Statistical analysis showed significant differences (P = 0.050) for the EAA (essential amino acids) index, which was highest for TB muscle, followed by BF and SM muscles, while the lowest values were reported by ST muscle. Finally, foal meat seems to be a very good nutritional source of major and minor minerals. The higher nutritional value of foal meat will be of great importance in the promotion of this meat.     

Effect of method of delivery of sodium butyrate on maturation of the small intestine in newborn calves

The effect of sodium butyrate (SB) supplementation in milk replacer (MR), starter mixture (SM), or both on small intestine maturation in newborn calves was investigated. Twenty-eight male calves with a mean age of 5 (±1) d were randomly allocated into 1 of 4 groups (7 animals per group) and fed (1) MR and SM, without SB (MR⁻ and SM⁻, respectively; MR⁻/SM⁻); (2) MR⁻ and SM supplemented with SB encapsulated within triglyceride matrix (SM⁺, 0.6% as fed; MR⁻/SM⁺); (3) MR supplemented with crystalline SB (MR⁺, 0.3% as fed) and SM⁻ (MR⁺/SM⁻); or (4) MR⁺ and SM⁺ (MR⁺/SM⁺). The MR was offered in amounts equal to 10% of initial body weight of the calf. The SM was blended with whole corn grain (50/50; wt/wt) and offered ad libitum as a starter diet. Calves were slaughtered at 26 d (±1) of age and small intestine development was investigated. Treatment with MR⁺ decreased villus height in the proximal jejunum and decreased villus height, crypt depth, and tunica mucosa thickness in the middle jejunum, whereas treatment with SM⁺ tended to increase small intestine weight and crypt depth in the proximal jejunum, and increased villus height in the distal jejunum. In the duodenum, crypt depth and tunica mucosa thickness were greater for the MR⁻/SM⁺ group compared with MR⁻/SM⁻, MR⁺/SM⁻, and MR⁺/SM⁺ groups. In the ileum, crypt depth was less for MR⁻/SM⁺ compared with MR⁻/SM⁻. Supplementation with SB in both MR and SM enhanced cell proliferation and decreased apoptosis in the middle jejunum mucosa. Regarding brush border enzyme activities, addition of SB to MR increased lactase activity in the middle jejunum and maltase activity in the distal jejunum, and tended to increase lactase activity in the distal jejunum, aminopeptidase A activity in the middle jejunum and ileum, and aminopeptidase N activity in the ileum. In contrast, SM⁺ increased dipeptidylpeptidase IV activity in the distal jejunum and tended to increase aminopeptidase N in the distal jejunum. In conclusion, both MR⁺ and SM⁺ affected small intestine development in newborn calves. This effect depended on the method of SB delivery but MR⁺ generally had a more pronounced effect. No synergistic effect of SB supplementation into MR and SM was found.     

Influence of molecular weight and degree of substitution of carboxymethylcellulose on the stability of acidified milk drinks

The influence of molecular weight (M_w, 250,000, 700,000) and degree of substitution (DS, 0.7, 0.9 and 1.2) of carboxymethylcellulose (CMC) on the diameter and ζ-potential of casein micelles during acidification in diluted dispersions and on the stability of acidified milk drinks was investigated. The experimental results suggested that CMC with high M_w or low DS would result in thick adsorbed layer onto casein micelles. The ζ-potential of CMC-coated casein micelle increased with increasing the M_w of CMC with the same DS while at a fixed M_w the ζ-potential for CMC with high DS (1.2) increased in comparison with those for CMC with low DS (0.7 and 0.9). Both M_w and DS of CMC influenced the stability of acidified milk drinks. CMC with high M_w increased the viscosity of acidified milk drinks significantly and therefore contributed to the stability. CMC with high DS resulted in high ζ-potential of CMC-coated casein micelles, increasing the electrostatic repulsion between casein particles, which prevented the phase separation in acidified milk drinks. It was also found that the amount of CMC needed for efficient coverage of casein micelles increased with increasing the M_w of CMC. Above the efficient coverage concentration, the long-term stability of acidified milk drinks with high M_w CMC was better than that with low M_w CMC.     

Effects of rapid chilling of carcasses and time of deboning on weight loss and technological quality of pork semimembranosus muscle

The effect of rapid air chilling of carcasses in the first 3 h of chilling at −31 °C (then at 2–4 °C, till 24 h post-mortem) and the possibility of earlier deboning (8 h post-mortem) after rapid air chilling, compared to conventional air chilling (at 2–4 °C, till 24 h post-mortem) on weight loss and technological quality (pH value, tenderness, drip loss, cooking loss and colour - L^*a^*b^* values) of pork M. semimembranosus was investigated. Under the rapid chilling conditions, weight loss was 0.8% at 8 h post-mortem and increased to 1.4% at 24 h post-mortem when weight loss was 2.0% under conventional chilling. Carcasses that were rapid chilled had significantly lower (P < 0.001) internal temperature in the deep leg at 4 (25.7 °C), 6 (13.0 °C), 8 (6.2 °C) and 24 h (3.8 °C) post-mortem compared to conventional chill treatment (32.7, 24.2, 19.1 and 5.1 °C, respectively). Rapid chilling reduced significantly (P < 0.05) the rate of pH value decline at 8 h (6.02) post-mortem in M. semimembranosus compared to conventional chill treatment (5.88). Compared to conventional chilling, in M. semimembranosus deboned in different time post-mortem, rapid chilling had a positive significant effect on drip loss (P < 0.05, muscles deboned 8 h post-mortem), cooking loss (P < 0.001) and incidence of pale colour (L^* value). Rapid chilling i.e. rapid chilling and earlier deboning had neither positive nor negative significant effects (P > 0.05) on other investigated technological quality parameters of M. semimembranosus (tenderness, a^* value and b^* value) compared to conventional chilling.     

Use of tea extracts for inhibition of polyphenoloxidase and retardation of quality loss of Pacific white shrimp during iced storage

Green tea and mulberry tea powder with and without prior chlorophyll removal were extracted with water and ethanol (800 mL L⁻¹). Extraction yield and total phenolic content of green tea extract were higher than those of mulberry tea extract, regardless of extraction media (P < 0.05). Extracts from green tea with and without prior chlorophyll removal showed the higher polyphenoloxidase (PPO) inhibitory activity, compared with mulberry tea extract, at the concentration used (0.1, 0.5 or 1 g L⁻¹). Additionally, green tea extracts had the higher reducing power, 2,2-diphenyl-1-picryl hydrazyl (DPPH) radical scavenging activities and copper chelating activity, compared with mulberry tea extract (P < 0.05). Ethanolic green tea extract with prior chlorophyll removal contained (+)-catechin (C), (−)-epicatechin (EC), (−)-epigallocatechin (EGC), (−)-epigallocatechin gallate (EGCg) and (−)-epicatechin gallate (ECG) at the levels of 242, 33.4, 125.6, 140.6 and 25.2 g kg⁻¹ dry extract, respectively. Whole white shrimp (Litopenaeus vannamei) treated with ethanolic green tea extract with prior chlorophyll removal at concentrations of 5 and 10 g L⁻¹ and stored in ice for up to 12 days had the lower psychrophilic bacterial count and lipid oxidation, compared with the control and shrimp treated with 12.5 g L⁻¹ sodium metabisulfite (SMS) (P < 0.05). Shrimp treated with 5 g L⁻¹ ethanolic green tea extract with prior chlorophyll removal possessed the lower melanosis, compared with the control, and showed similar score to those treated with SMS (P > 0.05). Furthermore, ethanolic green tea extract with prior chlorophyll removal had no adverse impact on sensory attributes of treated shrimp.     

Evaluation of the shifting of the line of sight and higher order aberrations of eyes with keratoconus after corneal cross-linking

Aim

To evaluate changes in the coordinates of the line of sight (LoS) and higher order aberrations (HOAs) of eyes with keratoconus, following corneal cross-linking (CXL).

Microencapsulation of probiotic cells by means of rennet-gelation of milk proteins

Probiotic cells were microencapsulated in milk protein matrices by means of an enzymatic induced gelation with rennet. Water insoluble, spherical capsules with a volume-based median of 68 ± 5 μm were obtained from a novel developed emulsifying and subsequent internal gelation process. A high encapsulation yield was found due to the encapsulation procedure for Lactobacillus paracasei ssp. paracasei F19 and Bifidobacterium lactis Bb12. After incubation at low pH-values, microencapsulation yielded higher survival rates compared to non-encapsulated probiotic cells. The viable cell numbers of encapsulated Lactobacillus paracasei and Bifidobacterium lactis were 0.8 and 2.8 log units CFU g⁻¹ higher compared to free cells after 90 min incubation at pH 2.5. The improved survival of encapsulated cells can probably be explained by a higher local pH-value within the protein matrix of the capsules caused by the protein buffering capacity, protecting the cells during incubation under simulated gastric conditions at low pH. The study indicates that rennet-induced gelation of skim-milk concentrates for the microencapsulation of probiotic cells can be a suitable alternative to current available technologies, mainly based on ionotrophic gelation of plant-polymer solutions.