显齿蛇葡萄中黄酮类化合物对α-葡萄糖苷酶的抑制作用研究

目的:研究显齿蛇葡萄醇提物及8种主要黄酮化合物对α-葡萄糖苷酶的抑制作用。方法:用75%无水乙醇回流提取制备显齿蛇葡萄提取物,对其进行α-葡萄糖苷酶抑制实验。之后选取显齿蛇葡萄中8种主要黄酮化合物对α-葡萄糖苷酶的抑制效果进行分析。结果:醇提物在(0.1~1.0)mg/mL之间对α-葡萄糖苷酶具有明显的抑制作用,其半抑制浓度(IC50)为0.338mg/mL。8种黄酮化合物均对α-葡萄糖苷酶产生不同程度的抑制作用,其中槲皮素的抑制效果最强,半抑制浓度为0.083 mg/mL,是醇提物的1/4。结论:显齿蛇葡萄醇提物与主要黄酮化合物对α-葡萄糖苷酶具有较明显的抑制作用,为显齿蛇葡萄进一步开发与利用提供了理论基础。     

枳椇果梗多糖的提取工艺优化及其抗氧化性

为获得枳椇果梗多糖,并进一步评价其自由基清除及抑制生物大分子(蛋白质、脂质、DNA)氧化的能力。以枳椇果梗为试验材料,在单因素实验的基础上,结合正交试验及方差分析优化枳椇果梗多糖热水提取工艺条件;对所提多糖清除DPPH、ABTS+自由基能力进行测定;并利用Cu²⁺/H₂O₂、FeSO₄、APPH分别诱导牛血清蛋白、亚油酸、鲱鱼精子DNA氧化,构建体外蛋白质、脂质、DNA氧化模型,对所提多糖体外抑制生物大分子氧化能力进行评价。结果表明：醇沉体积分数对枳椇果梗多糖的得率有显著性(P<0.05)的影响,最佳的热水提取工艺条件为：料液比1:25 g/mL,提取温度85℃,提取时间1 h,醇沉体积分数80%,此时多糖得率为3.06%±0.181%;且随着浓度的增大,所提多糖对自由基的清除和生物大分子的氧化抑制效果也逐渐提高,对DPPH自由基、ABTS+自由基清除IC₅₀分别为1.687、1.824 mg/mL,对牛血清蛋白羰基化、亚油酸过氧化和鲱鱼精子DNA氧化抑制IC50分别为：...     

枇杷抑制α-葡萄糖苷酶和α-淀粉酶活性部位的筛选及其酶动力学

比较研究枇杷不同药用部位(根、茎、叶、花、果肉、种子)醇提取物对α-葡萄糖苷酶和α-淀粉酶抑制活性,并探究最强活性部位及其总黄酮的酶促反应动力学特征。采用95%乙醇超声提取制备枇杷不同药用部位醇提取物,超声辅助浸提并经AB-8大孔树脂制备总黄酮,利用紫外光谱法测定α-葡萄糖苷酶和α-淀粉酶抑制活性,通过酶促动力学方法与Lineweaver-Burk曲线推断酶抑制类型。结果表明,枇杷不同药用部位醇提取物均具有一定的α-葡萄糖苷酶和α-淀粉酶抑制活性,α-葡萄糖苷酶抑制活性强弱依次为花>茎>根>叶>果肉>种子,α-淀粉酶抑制活性强弱依次为根>茎>花>叶>果肉>种子。枇杷花醇提取物、枇杷花总黄酮对α-葡萄糖苷酶抑制活性半抑制浓度(half inhibitory concentration, IC₅₀)值分别为(4.65±0.35)、(0.017 4±0.003 5) g/L,均为可逆非竞争性抑制类型;对α-淀粉酶抑制活性IC₅₀值分别为(14.41±0.59)、(1.57±0.03)g/L...     

桑黄提取物的体外抗氧化、降血糖及降尿酸活性

为了解杨树桑黄不同提取物的生物活性,采用超声辅助法制备了杨树桑黄粗多糖和醇提物,分析了二者主要成分及其含量,比较了二者体外抗氧化、降血糖及降尿酸活性。研究发现桑黄粗多糖中总糖含量为74.87%,蛋白质含量为6.61%,糖醛酸含量为4.84%,硫酸基含量为2.59%;桑黄醇提物中总酚含量为35.72%,总黄酮含量为8.98%,总三萜含量为5.82%,总甾醇含量为7.36%。此外,桑黄粗多糖和醇提物具有较强的DPPH自由基、ABTS自由基、羟自由基清除能力和一定的还原力。体外降血糖及降尿酸实验表明桑黄多糖和醇提物对α-淀粉酶、α-葡萄糖苷酶与黄嘌呤氧化酶均有一定抑制作用,但桑黄醇提物降血糖和降尿酸活性明显优于桑黄多糖;另外桑黄醇提物对α-葡萄糖苷酶抑制作用IC50值为0.43 mg/mL,远低于阿卡波糖IC50值（0.87 mg/mL）。与桑黄多糖相比,桑黄醇提物具有较强的体外抗氧化、降血糖及降尿酸活性,这为充分利用桑黄资源、开发桑黄功能性食品或医药保健品提供了理论依据。     

准噶尔山楂叶抗氧化及抑制α-葡萄糖苷酶活性

采用超声提取不同月份准噶尔山楂叶,系统溶剂萃取其醇提物得到环己烷部位、乙酸乙酯部位、正丁醇部位和水部位,分别测定其总黄酮含量,通过清除DPPH自由基、铁离子还原能力和α-葡萄糖苷酶抑制活性评价准噶尔山楂叶不同提取物的体外抗氧化活性及降血糖活性。结果表明,准噶尔山楂叶各提取物均有不同程度的抗氧化和α-葡萄糖苷酶抑制活性,其中以总黄酮含量最高的乙酸乙酯部位(28.87 mg/g)效果最佳,其对DPPH清除活性(IC_(50)=0.026 mg/m L)远强于阳性对照BHA(IC_(50)=0.996 mg/m L),α-葡萄糖苷酶抑制活性(IC_(50)=191.71 g/m L)高于阳性对照阿卡波糖(IC_(50)=1 044.32 g/m L)。各提取物体外抗氧化和降血糖活性与其总黄酮含量呈正相关性,说明黄酮类化合物为影响其活性的主要因素。     

槐花醇提物对α-淀粉酶、α-葡萄糖苷酶的抑制作用

试验研究了槐花醇提物对α-淀粉酶、α-葡萄糖苷酶的抑制作用,测定了槐花醇提取物中多酚含量,考察了槐花醇提物对α-淀粉酶、α-葡萄糖酶的抑制作用及抑制作用类型。结果显示,槐花醇提物中多酚含量为18.271μg/g,高于水提物;槐花醇提物对这两种酶均具有一定的抑制作用,槐花醇提物对α-淀粉酶活性最大抑制率仅为47.20%,槐花醇提物对α-葡萄糖苷酶活性抑制最大抑制率可达81.32%,其IC50为9.16 mg/L。动力学分析结果显示,低浓度和高浓度的槐花醇提物对α-淀粉酶、α-葡萄糖苷酶活性抑制均为混合性抑制。     

不同蕨菜制品醇提物体外抗氧化及降血糖活性研究

目的:比较研究不同蕨菜制品醇提取物的体外抗氧化和降血糖活性。方法:分别采用Folin-Ciocalteu法、NaNO₂ -Al（NO₃）₃法测定总酚和总黄酮含量;通过DPPH法、ABTS法、普鲁士蓝法、α-葡萄糖苷酶和α-淀粉酶的抑制活性评价体外抗氧化、降血糖活性;Pearson法分析成分含量与活性的相关性。结果:不同蕨菜醇提物的总酚和总黄酮含量、抗氧化活性、α-葡萄糖苷酶和α-淀粉酶抑制活性差异显著。其中鲜品醇提取物的总酚、总黄酮含量最高,分别可达（593±3.45）mg GA/g、（156.75±1.28）mg RT/g,且鲜品醇提取物铁离子还原能力、ABTS自由基清除能力、DPPH自由基清除能力最强;湿品醇提取物对α-葡萄糖苷酶、α-淀粉酶的抑制作用最强。不同蕨菜醇提取物总酚、总黄酮的含量与其抗氧化活性均呈极显著正相关关系（P<0.01）,与降血糖活性均呈显著正相关关系（P<0.05）。结论:蕨菜鲜品抗氧化活性较强,湿品降血糖活性较强,可能活性成分为多酚类和黄酮类成分。     

漆酶催化二氢杨梅素氧化聚合

系统考察漆酶催化条件对二氢杨梅素衍生物的颜色、α-葡萄糖苷酶抑制及抗氧化活性的影响,并运用波谱手段对产物结构进行表征.结果表明漆酶可用于二氢杨梅素的氧化聚合,且漆酶浓度、pH值、反应时间及温度对衍生物的颜色有规律性影响.所得二氢杨梅素衍生物的α-葡萄糖苷酶抑制活性(IC506.2μg/mL)显著高于二氢杨梅素(IC50...     

广金钱草不同极性萃取物体外降脂及降血糖活性的比较

该研究旨在比较广金钱草乙醇提取物及其各萃取相的体外降脂及降血糖活性。以φ=75%乙醇为溶剂，回流提取得到广金钱草醇提物，经石油醚、乙酸乙酯、正丁醇、水依次萃取，利用比色法检测乙醇提取物及各萃取相中总黄酮、总酚含量，并根据胰脂肪酶和胆固醇酯酶的抑制率评价乙醇提取物及其各萃取相的体外降脂活性，对α-葡萄糖苷酶和α-淀粉酶的抑制率评价体外降血糖活性。研究结果显示乙酸乙酯萃取相中总黄酮和总酚含量最高，分别为154.57 mg/g和34.27 mg/g。乙醇提取物对胆固醇酯酶和α-葡萄糖苷酶的抑制活性最高，抑制率分别为53.24%和68.52%；正丁醇萃取相对胰脂肪酶表现出最高的抑制活性，抑制率达到77.39%。石油醚萃取相对α-淀粉酶的抑制作用最强，抑制率达到78.60%。研究表明，广金钱草乙醇提取物及其各萃取相具有显著的降脂和降血糖活性，可为其深入研究药理活性提供参考依据。     

刺梨总三萜提取方法及其α-葡萄糖苷酶抑制活性研究

以药食两用植物刺梨为对象,研究不同提取方法对提取刺梨总三萜影响及其最佳方法下总三萜的α-葡萄糖苷酶抑制活性。通过采用5种不同提取方法(水煮醇沉法、回流提取法、大孔树脂法、浸渍法、超临界萃取法)对总三萜提取率,α-葡萄糖苷酶抑制模型对总三萜抑制活性进行考察。结果表明,回流提取法刺梨总三萜提取率最高,为0.53%;其三萜总提物经处理所得A、B部分α-葡萄糖苷酶抑制活性较好(IC50值分别为9.6、3.4μg/mL),活性远优于阳性对照阿卡波糖(IC50=75.2μg/mL)。该提取方法经济、方便、适合工业化生产,且三萜总提物具有较好的α-葡萄糖苷酶抑制活性。     

Ovarian structures and circulating steroids in heifers and lactating cows in summer and lactating and dry cows in winter

Two experiments compared follicular and luteal development and circulating steroid concentrations from induced luteolysis to ovulation in lactating Holstein cows (n = 27; 40.0 +/- 1.5 kg milk/day) vs. nulliparous heifers (n = 28; 11 to 17 mo-old) during summer (Experiment 1), and in lactating (n = 27; 45.9 +/- 1.4 kg milk/d) vs. dry cows (n = 26) during winter (experiment 2). All females received PGF2,, 6 d after ovulation and were monitored until next ovulation by daily ultrasound and assay of serum progesterone (P4) and estradiol (E2). Every female was used two or three times. In Experiment 1, lactating cows had high incidence of multiple ovulation (63.5%) compared with heifers (1.3%). Among single ovulators, there was no difference in maximal size of ovulatory follicles between lactating cows and heifers (15.8 vs. 16.5 mm, respectively). However, lactating cows had lower peak serum E2 (8.6 vs. 12.1 pg/ml), took longer to ovulate after luteolysis (4.6 vs. 3.8 d), developed more luteal tissue volume (7,293.6 vs. 5,515.2 mm3), and had lower serum P4 on d 6 after ovulation (2.0 vs. 3.0 ng/ml) than heifers (data included multiple ovulators). In experiment 2, multiple ovulations were similar between lactating and dry cows (17.9 vs. 17.2%, respectively). Peak serum E2 was also similar between lactating and dry cows (7.6 vs. 8.5 pg/ml) although lactating cows had larger ovulatory follicles (18.6 vs. 16.2 +/- 0.4 mm). Lactating cows took longer to ovulate (4.8 vs. 4.2 d), developed more luteal tissue (7,599 vs. 5,139 +/- 468 mm3), but had similar serum P4 (2.2 vs. 1.9 ng/ ml) compared with dry cows. Therefore, lactating cows had similar or lower circulating steroid concentrations than dry cows or heifers, respectively, despite having larger ovarian structures.     

Fertilization and early embryonic development in heifers and lactating cows in summer and lactating and dry cows in winter

Two experiments in two seasons evaluated fertilization rate and embryonic development in dairy cattle. Experiment 1 (summer) compared lactating Holstein cows (n = 27; 97.3 +/- 4.1 d postpartum [dppl; 40.0 +/- 1.5 kg milk/d) to nulliparous heifers (n = 28; 11 to 17 mo old). Experiment 2 (winter) compared lactating cows (n = 27; 46.4 +/- 1.6 dpp; 45.9 +/- 1.4 kg milk/d) to dry cows (n = 26). Inseminations based on estrus included combined semen from four high-fertility bulls. Embryos and oocytes recovered 5 d after ovulation were evaluated for fertilization, embryo quality (1 = excellent to 5 = degenerate), nuclei/embryo, and accessory sperm. In experiment 1, 21 embryos and 17 unfertilized oocytes (UFO) were recovered from lactating cows versus 32 embryos and no UFO from heifers (55% vs. 100% fertilization). Embryos from lactating cows had inferior quality scores (3.8 +/- 0.4 vs. 2.2 +/- 0.3), fewer nuclei/embryo (19.3 +/- 3.7 vs. 36.8 +/- 3.0) but more accessory sperm (37.3 +/- 5.8 vs. 22.4 +/- 5.5/embryo) than embryos from heifers. Sperm were attached to 80% of UFO (17.8 +/- 12.1 sperm/UFO). In experiment 2, lactating cows yielded 36 embryos and 5 UFO versus 34 embryos and 4 UFO from dry cows (87.8 vs. 89.5% fertilization). Embryo quality from lactating cows was inferior to dry cows (3.1 +/- 0.3 vs. 2.2 +/- 0.3), but embryos had similar numbers of nuclei (27.2 +/- 2.7 vs. 30.6 +/- 2.1) and accessory sperm (42.0 +/- 9.4 vs. 36.5 +/- 6.3). From 53% of the flushings from lactating cows and 28% from dry cows, only nonviable embryos were collected. Thus, embryos of lactating dairy cows were detectably inferior to embryos from nonlactating females as early as 5 d after ovulation, with a surprisingly high percentage of nonviable embryos. In addition, fertilization rate was reduced only in summer, apparently due to an effect of heat stress on the oocyte.     

2018年深圳市售蔬菜和鸡蛋中氟虫腈及其代谢物的检测分析

目的 建立超高效液相色谱-串联质谱法同时测定蔬菜和鸡蛋中氟虫腈及其代谢物(氟甲腈、氟虫腈砜和氟虫腈亚砜), 并对深圳市售的蔬菜和鸡蛋中氟虫腈及其代谢物残留状况进行抽样检测。方法 采用QuEChERS前处理方法, 以C18色谱柱为分离柱, 以乙腈和10 mmol甲酸+6 mmol甲酸铵水溶液为流动相进行梯度洗脱, 用超高效液相色谱-串联质谱(ultra performance liquid chromatography-mass spectrometry/mass spectrometry, UPLC-MS/MS), 电喷雾电离(electrospray ionization, ESI), 多反应监测(multiple reaction monitoring, MRM)模式检测, 外标法同时定量测定氟虫腈及其代谢物。结果 方法的线性范围为0.1~2.0 μg/L, 线性相关系数均大于0.9994, 检出限0.0005 mg/kg, 定量限0.001 mg/kg; 蔬菜中3个水平的平均加标回收率88.0%~101.2%, 相对标准偏差(relative standard deviation, RSD)均小于8.5%; 鸡蛋中3个水平的平均加标回收率86.1%~104.8%, 相对标准偏差(RSD)均小于9.2%。结论 该方法具有操作简单、干扰少、快速、准确可靠等特点, 可适用于蔬菜鸡蛋中氟虫腈及其代谢物的检测。     

Sweetness and aroma perceptions in dairy desserts varying in sucrose and aroma levels and in textural agent

Sweetness–aroma interactions were investigated in model dairy desserts varying in sucrose concentration, aroma concentration and in textural characteristics using different textural agents (κ-, ι-, λ-carrageenans and an equal-mix of the three). Overall intensities of sweetness and aroma perceptions were evaluated by sensory analysis and apparent partition coefficients of aroma compounds were measured by static headspace—GC.Sweetness–aroma interaction was characterised by a non-reciprocal relationship. Concentration of aroma had no impact on sweetness intensity, whatever be the sucrose concentration or textural characteristics of desserts, whereas varying texture or sucrose concentration modified aroma intensity. However, effects on aroma assessment were effective only when aroma concentration was the highest. In this condition, use of λ-carrageenan or increasing sucrose concentration from 25 to 50 g kg⁻¹ enhanced aroma intensity, but no extra enhancement was observed when sucrose concentration was 100 g kg⁻¹. As the air–dessert partition coefficient remained constant, impact of textural characteristics and sweetness variation on aroma perception did not result from physico-chemical interaction.     

Aluminium and fluoride in hospital daily diets and in teas

The levels of aluminium and fluoride have been determined in hospital daily diets including breakfast, dinner and supper, as well as in black teas and herbal teas purchased from the local market. In tea, aluminium was determined directly in a sample solution by atomic absorption spectroscopy using nitrous oxide and an acetylene flame. For analysis of the hospital diet, samples containing lower levels of aluminium were analysed using a spectrophotometric method which measured aluminium in the form of a 8-hydroxyquinoline complex. Decomposition of the samples was achieved using a mixture of concentrated acids [nitric (HNO₃), perchloric (HClO₄) and sulphuric (H₂SO₄)] in platinum dishes. Fluoride was assayed by spectrophotometry using a microdiffusion procedure with a mixture of concentrated HClO₄ and silver sulphate, trace amounts of the released fluoride [as hydrogen fluoride (HF)] were trapped on the alkaline surface of a Petri dish and then determined in the form of an alizarin-fluoride complex. The mean level of aluminium found in hospital daily diets amounted to 21.3±12.3 mg and the mean level of fluoride was 1.38±1.12 mg per adult person. In the 16 samples of commercially available brands of black teas, the levels of aluminium and fluroide ranged from 445 to 1552 ppm (mean=897±264 ppm) and from 30 to 340 ppm (mean 141±85 ppm), respectively. In six herbal teas, the mean levels of aluminium and fluoride were lower, and amounted to 218.9±150.7 ppm and 6.0±6.9 ppm, respectively. This study has shown that concern about a high intake of aluminium and fluoride from these foods is unfounded.     

芝麻饼粕及其在烟草上应用研究现状

概述了芝麻饼粕的有效营养成分及其作为有机肥的加工方法,介绍了芝麻饼粕在烟草生产上的应用效果。并就进一步促进芝麻饼粕在烟草上的应用提出了建议,以期为烟叶生产过程中科学使用芝麻饼粕提供参考资料。     

Heavy metals in vegetables grown in The Netherlands and in domestic and imported fruits

The contents of cadmium, lead mercury, copper, manganese and zinc in 242 samples of 37 different species of domestic and imported fruits have been determined. Also contents of the same heavy metals, except mercury, have been determined in 205 samples of 7 species of domestic vegetables (lettuce, spinach, endive, beetroots, onions, celeriac and Swedish turnips). The median contents (in mg/kg fresh mass of the edible part) found for fruits are: Cd 0.002; Pb 0.017; Hg 0.002; Cu 0.61; Mn 0.52 and Zn 0.99. In the vegetables median levels have been found (mg/kg) of 0.009-0.073 for Cd, 0.01-0.03 for Pb, less than 0.2-0.3 for Cu, 0.69-1.41 for Mn and 0.95-5.5 for Zn. The contribution of fruits to the tolerable daily intakes of Cd, Pb and Hg is, for an average consumption pattern, less than 1%. On the other hand, the contribution to the recommended amounts of the essential elements Cu, Mn, and Zn is no more than 1%-3%. From the vegetables an average portion of spinach contains 19% and 2.6% of the tolerable daily amounts of Cd and Pb, respectively. For the other species of vegetables these figures are less than 5% for Cd (except for endive, 6.8%) and for lead less than 1%. Spinach contributes considerably to the need for Cu, Mn and Zn, in general more than 10% of the recommended daily amounts. The other species of vegetables contribute only from less than 1% to less than few percents.     

Heavy metals in vegetables grown in the Netherlands and in domestic and imported fruits

Summary The contents of cadmium, lead mercury, copper, manganese and zinc in 242 samples of 37 different species of domestic and imported fruits have been determined. Also contents of the same heavy metals, except mercury, have been determined in 205 samples of 7 species of domestic vegetables (lettuce, spinach, endive, beetroots, onions, celeriac and Swedish turnips). The median contents (in mg/kg fresh mass of the edible part) found for fruits are: Cd 0.002; Pb 0.017; Hg 0.002; Cu 0.61; Mn 0.52 and Zn 0.99. In the vegetables median levels have been found (mg/kg) of 0.009–0.073 for Cd, 0.01–0.03 for Pb, <0.2–0.3 for Cu, 0.69–1.41 for Mn and 0.95–5.5 for Zn. The contribution of fruits to the tolerable daily intakes of Cd, Pb and Hg is, for an average consumption pattern, less than 1%. On the other hand, the contribution to the recommended amounts of the essential elements Cu, Mn, and Zn is no more than 1%–3%. From the vegetables an average portion of spinach contains 19% and 2.6% of the tolerable daily amounts of Cd and Pb, respectively. For the other species of vegetables these figures are less than 5% for Cd (except for endive, 6.8%) and for lead less than 1%. Spinach contributes considerably to the need for Cu, Mn and Zn, in general more than 10% of the recommended daily amounts. The other species of vegetables contribute only from less than 1% to less than few percents.

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Schwermetalle in niederländischen Gemüsen und in inländischem und importiertem Obst

Zusammenfassung Es wurde der Gehalt an Cadmium, Blei, Quecksilber, Kupfer, Mangan und Zink in 242 Proben von 37 verschiedenen Fruchtarten, landeseigenen und importierten, bestimmt. Darüber hinaus wurde der Gehalt der gleichen Schwermetalle, außer Qeucksilber, in 205 Proben von 7 Sorten landeseigenen Gemüsen, Kopfsalat, Spinat, Endivie, rote Rüben, Zwiebeln, Sellerie und Kohlrüben ermittelt. Die Medianwerte (in mg/kg Frischsubstanz des eßbaren Anteils) für die Fruchtproben sind: Cd 0,002; Pb 0,017; Hg 0,002; Cu 0,61; Mn 0,52; Zn 0,99. In den Gemüsen betrugen die Medianwerte (mg/kg) für Cd 0,009–0,073, für Pb 0,01–0,03, für Cu <0,2–1,3, für Mn 0,69–1,41 und für Zn 0,95–5,5. Der Anteil an den duldbaren täglichen Aufnahmemengen für Cd, Pb und Hg liegt bei durchschnittlichem Verzehr von Früchten unterhalb 1%. Andererseits ist der Anteil der Früchte an den empfohlenen Mengen für die essentiellen Spurenelemente Cu, Mn und Zn bei normalem Verzehr auch nur 1%–3%. Bei den Gemüsen liefert eine Tagesportion Spinat im Durchschnitt 19% bzw. 2,6% der duldbaren täglichen Menge an Cd bzw. an Pb; bei den übrigen Gemüsearten macht das Cd weniger als 5% (außer Endivie 6,8%) und das Pb weniger als 1% aus. Spinat liefert einen wesentlichen Anteil des Bedarfs an Cu, Mn und Zn von über 10%. Der Beitrag der übrigen Gemüsearten ist im Durchschnitt nur einige Prozent.

     

Characterization of limestones and their effects in vitro and in vivo in dairy cattle

Capacities of limestones of differing particle size to neutralize acid in vitro and to modify pH and utilization of feedstuffs in vivo were compared. Acid neutralization during pH-stat titrations was faster for fine than for coarse limestone, and mixed microbial cultures were more resistant to pH change when they contained fine calcium carbonate. Diets containing 25:75 corn silage to concentrates and .95% calcium from either coarse or fine limestone were fed to rumen-fistulated heifers. Total ruminal volatile fatty acid concentrations were higher for the fine limestone treatment. Ruminal volumes, dry matter disappearance, and ruminal fluid pH and dilution rate did not differ between fine and coarse limestone treatments. Ruminal fluid volume, osmolality, ratios of acetate to propionate, and concentrations of total volatile fatty acids were unaffected in rumen-fistulated Holstein cows fed 60:40 corn silage to concentrates and either .5% calcium (control) or 1.0% calcium from either coarse or fine limestone. Ruminal pH increased .07 to .10 units with limestone supplementation. Ruminal fluid dilution and particulate turnover rates were slower for the coarse limestone than the control treatment. Differences between coarse and fine limestones in vitro were observed under some conditions in vivo, but they were not consistent.     

Flavour and vitamin stability in pasteurized milk in polyethylene-coated cartons and in polyethylene bottles

Commercially pasteurized, non-homogenized full cream milk in 2-pt white polyethylene (PE)-coated cartons overprinted with blue, and in 4-pt PE bottles was stored for 4 d in the dark or under white fluorescent light of 4000 1x, at a temperature of 7°C. The flavour of milks kept in the dark remained good, but exposure to light resulted in early off-flavour development: cartoned milk was disliked by a flavour panel after about 17.5 h exposure and milk in the PE bottles after 9 h. Vitamins A and B₂ were stable in the milk during 4 d storage in the dark in both bottles and cartons, and in cartons exposed to light. In the bottled milks, light-induced losses of these vitamins after 4 d were, respectively, 15% and 35%. but there was little or no loss before the development of light-induced flavour. Loss of total vitamin C by day 4 was about 50% in the dark, irrespective of container. In the cartons exposed to light, 66% of the vitamin C was lost, while virtually none remained in the exposed, bottled milk. There was also a markedly greater loss of vitamin C in the bottled milk than in the cartoned milk at the time the flavour became unacceptable. The dissolved O₂ concentration dropped considerably in the bottled milk exposed to light, but only marginally in the cartons. There were small increases in dissolved O₂ in the dark in both types of container.