Insights to the clarification of sugar cane juice expressed from sugar cane stalk and trash

Processing of juice expressed from green sugar cane containing all the trash (i.e., tops and leaves, the nonstalk component) of the sugar cane plant during sugar manufacture has been reported to lead to poor clarified juice (CJ) quality. Studies of different liming techniques have been conducted to identify which liming technique gives the best clarification performance from juice expressed from green cane containing half of all trash extracted (GE). Results have shown that lime saccharate addition to juice at 76 °C either continuous or batchwise gives satisfactory settling rates of calcium phosphate flocs (50-70 cm/min) and CJ with low turbidity and minimal amounts of mineral constituents. Surprisingly, the addition of phosphoric acid (≤ 300 mg/kg as P?O?), prior to liming to reduce juice turbidity (≤ 80%), increased the Mg (≤ 101%) and Si (≤ 148%) contents particularly for clarified GE juices. The increase was not proportional with increasing phosphoric acid dose. The nature of the flocs formed, including the zeta potential of the particles by the different liming techniques, has been used to account for the differences in clarification performance. Differences between the qualities of the CJ obtained with GE juice and that of burnt cane juices with all trash extracted (BE) have been discussed to provide further insights into GE processing.     

Preheating and incubation of cane juice prior to liming: a comparison of intermediate and cold lime clarification.

In the U.S., cold lime clarification remains the clarification process of choice in raw sugar manufacturing. A comparative study of cold vs intermediate lime clarification was undertaken at a factory that operated intermediate liming (approximately 30% mixed juice (MJ) of pH 5.2 +/- 0.3 was preheated to 87-93 degrees C to help maintain clean limed juice heaters, incubated at approximately 54 degrees C, and then limed) but still had the pipes to revert to cold liming (MJ incubated and limed at approximately 40 degrees C) for this study. Hourly samples were collected over a 6 h sampling period across cold and intermediate clarification processes on two consecutive days, respectively, and this was repeated three times across the 1999 grinding season. A total of 1.57% less sucrose was lost to inversion reactions across intermediate rather than cold liming. In intermediate liming, which required approximately 4.6% less lime, preheating of only 30% of the MJ markedly removed color (-29%), dextran (-10%), and starch (-24%) and caused large flocs to form that settled faster in the clarifiers. Faster settling led to an impressive 4.6% (season average) more turbidity removal across the clarifiers in intermediate rather than cold liming. Intermediate clarified juice (CJ) turbidity (season average 2028 ICU +/- 675) was approximately half of cold CJ turbidity (average 3952 ICU +/- 1450) with over 2-fold more CJ turbidity control. Subsequent turbidity values and control were significantly improved in the final evaporator syrup samples too. For both processes, juice incubation caused approximately 10% color removal, but this was offset by color formation on liming, because of the alkaline degradation of invert; however, overall, more color was removed than formed in intermediate liming. Starch was reduced in the incubator tank, for both processes, because added filtrate reduced the acidity enabling natural diastase from the cane to degrade starch. Some dextran occasionally formed in the incubator tank, in both processes. Summed across measured parameters, intermediate liming appears to offer several advantages over cold liming.     

Apple juice clarification by immobilized pectolytic enzymes in packed or fluidized bed reactors

The catalytic behavior of a mixture of pectic enzymes, covalently immobilized on different supports (glass microspheres, nylon 6/6 pellets, and PAN beads), was analyzed with a pectin aqueous solution that simulates apple juice. The following parameters were investigated: the rate constant at which pectin hydrolysis is conducted, the time (tau(50)) in which the reduction of 50% of the initial viscosity is reached, and the time (tau(comp,dep)) required to obtain complete depectinization. The best catalytic system was proven to be PAN beads, and their pH and temperature behavior were determined. The yields of two bed reactors, packed or fluidized, using the catalytic PAN beads, were compared to the circulation flow rate of real apple juice. The experimental conditions were as follows: pH 4.0, T = 50 degrees C, and beads volume = 20 cm(3). The initial pectin concentration was the one that was present in our apple juice sample. No differences were observed at low circulation rates, while at higher recirculation rates, the time required to obtain complete pectin hydrolysis into the fluidized reactor was found to be 0.25 times smaller than in the packed bed reactor: 131 min for the packed reactors and 41 min for the fluidized reactors.     

壳聚糖澄清芦柑果汁工艺条件的优化

为了制备稳定的澄清芦柑果汁,该文基于Box-Behnken试验设计,探讨了壳聚糖浓度、澄清温度、澄清时间对果汁澄清度的影响;建立了二次多项式回归模型,分析模型的有效性与因子间的交互作用,并对壳聚糖澄清芦柑果汁的工艺参数进行了优化。结果表明：壳聚糖澄清芦柑果汁的最佳工艺参数为：壳聚糖浓度0.80 g/L、温度59℃和时间71 min。在此最佳工艺条件下果汁透光率达到97.8%,且试验结果与模型预测值（98.3%）相吻合,所得回归模型拟合情况良好（R2=0.9886）,达到设计要求。进一步对经壳聚糖澄清后的芦柑果汁的相关指标进行测定,发现果汁中可溶性固形物、维生素 C 及总酸含量依次从11.30±0.15%、31.33±3.25 mg/100mL、0.71±0.00 g/100mL略降为9.50±0.25%、21.8±5.28 mg/100mL、0.51±0 g/100mL,而总酚、果胶、蛋白质质量浓度依次从990.3±8.02 mg/L、366±4.70μg/mL、595.53±20.62μg/mL减少为557.87±4.67 mg/L、186.24±44.32μg/mL、26.42±0.30μg/mL 有较明显下降,但澄清后的果汁非生物稳定性很好。该试验用响应面法优选出的澄清工艺合理可行,为芦柑果汁深加工及果汁产品开发提供了理论依据。     

Spectrophotometric determination of urea in sugar cane distilled spirits

Urea is an important precursor in the formation of ethyl carbamate, a known carcinogen in alcoholic beverages. Ethyl carbamate has recently been detected at high concentrations in sugar cane distilled spirits, but little is known about the concentration of urea in these beverages. The objectives of this study were to validate methodology for the determination of urea in sugar cane distilled spirits, to determine the levels in 68 samples from different regions within the state of Minas Gerais, Brazil, and to examine the relationship between the concentrations of urea and ethyl carbamate. The method, based on the reaction of urea with 1-phenyl-1,2-propanodione-2-oxime and spectrophotometric quantification at 540 nm, provided linear response from 0.5 to 15.0 mg/L. No purification of the sample was required. The limits of detection and quantification were 0.1 and 0.5 mg/L, respectively. Urea was detected in 69% of the samples at levels varying from 0.50 to 5.10 mg/L. There was no significant difference on the levels of urea in samples from different regions of the state. No significant correlation between the levels of urea and ethyl carbamate was observed for the samples analyzed.     

施用炉渣灰对甘蔗产量和糖分含量的影响

莆田市地处福建省东南沿海,土壤淋溶强烈,缺硅比较严重,有效硅一般只有20～88mg/kg,粉渣灰是一种富含二氧化硅的工业废料,为了探讨其肥效,我们应用水泥炉渣灰进行甘蔗田间试验,取得了明显的效果.     

柑桔汁陶瓷膜微滤澄清和污染阻力试验

为了探讨柑桔汁微滤澄清技术及微滤膜污染阻力,建立膜清洗方法,研究以0.2 mm陶瓷膜微滤柑桔汁时膜通量变化及处理效果,结果表明：当温度30℃、压差0.16 MPa及膜面流速4 m/s时,全循环模式下稳定膜通量为22.4 L/(m2·h),浓缩模式下体积浓缩因子为12时,膜通量为10.6 L/(m2·h),澄清汁得率达91.67%;澄清汁浊度仅为0.62 NTU,澄清度高达99.93%,且各主要营养成分变化不大。通过建立膜污染阻力模型,考察操作参数对各分解阻力的影响,进而研究膜污染动力学后发现：压差对不可逆极化层阻力影响最为明显;增大膜面流速显著降低各极化层阻力,但对不可逆污染阻力作用不大;升高温度使得各阻力下降;膜污染可用拟二级速率方程描述。研究污染膜清洗过程,结果表明采用去离子水、1% NaOH和0.5% NaClO混合液、0.2% HNO3溶液依次清洗膜,膜通量可迅速恢复。     

无机陶瓷微滤膜对梨汁的澄清和除菌效果研究

该文研究了无机陶瓷微滤膜对梨汁的澄清和除菌效果的影响。采用3种孔径(0.8 μm、0.2 μm、50 nm)的氧化铝无机陶瓷微滤膜和自制的加压微滤装置进行试验。试验结果表明：3种膜微滤对梨汁的可溶性固形物、维生素C、还原糖含量和pH值的影响不大；50 nm和0.2 μm膜的澄清效果好于0.8 μm膜；50 nm膜澄清汁得率较低；0.2 μm和0.8 μm膜微滤澄清汁很好地保持了梨汁的风味。3种孔径膜微滤过程中，循环梨汁的温度在20～30℃之间；0.2 μm膜微滤过程中，有较好的通透量。50 nm膜除菌效果最好，微生物指标均达到国家食品卫生标准要求；0.2 μm和0.8 μm膜除菌效果不好。综合澄清效果、梨风味物质损失、膜通透量和除菌效果等指标可以看出，通过0.2 μm膜澄清梨汁的综合指标最好。     

Nitrogenase activity of sugar cane propagated from stem cuttings in sterile vermiculite

About one-quarter of 6- to 15-day old sugar cane (cv NA56-79) propagated from surface sterile or untreated single node cuttings in sterile vermiculite exhibited acetylene-reducing activity (ARA). Most of this ARA was in the rhizosphere vermiculite. There was no ARA before sprouting of the cuttings. There were numerous nitrogen-fixing and other bacteria in macerated untreated and macerated surface sterile cuttings, and nitrogen-fixers were enriched when small sections taken from internal tissues of cuttings were incubated on sucrose agar slants under air. Possible sites of N₂-fixers in the stem tissues, and possible routes of movement of these bacteria into the rhizosphere after germination were indicated by observations of distributions of tetrazolium-reducing bacteria. There was no evidence of progressive invasion of the stem from the surface inwards. It is suggested that the most likely origin of bacteria in the stem is in the root interior where tetrazolium-reducing bacteria were observed in the same types of sites as in the stems, viz. in intercellular spaces and in the xylem. Reestablishment of the stem bacteria in the roots and rhizosphere soil following germination appears to constitute an instance of cyclic infection. This phenomenon may be of significance historically, and potentially, to perpetuate and enhance N₂ fixation by sugar cane.     

鲜榨苹果汁陶瓷膜超滤澄清与除菌的中试试验研究

该研究应用膜孔径为100 nm的陶瓷膜错流超滤中试系统(MEMBRALOX^?,Pall)对果胶酶酶解后的鲜榨苹果原汁进行了过滤澄清与除菌效果研究。结果表明,100 nm陶瓷膜错流超滤的最佳操作条件为：跨膜压力为0.85×10⁵ Pa,温度为50℃,膜面流速为5 m/s;以0.5%次氯酸钠和4% NaOH溶液作为清洗剂,膜通量的恢复率可以达到98%。过滤后果汁中的悬浮颗粒和引起浊度升高的大分子胶体物质大部分被滤除,而果汁的各项质量指标如pH值、总酸、糖度等却未发生     

Use of green manures in increasing inputs of biologically fixed nitrogen to sugar cane

In this study the contribution of biological N₂ fixation (BNF) to several green manure crops used at planting of sugar cane, or in the inter-rows of the ratoon crop, was evaluated. The subsequent effects of these legumes on the N supply and yield of the sugar cane crop was also investigated. The experiment was conducted in an extremely sandy N-deficient soil over two consecutive years. In the first year the legumes were planted on the same day as the sugar cane and in the second year they were planted immediately after the harvesting of the cane. The treatments consisted of four legume species (Crotalaria juncea, C. spectabilis, Canavalia ensiformis and Mucuna deeringiana), 100 kg N as urea fertiliser in a split addition, and no fertiliser N addition. The legumes were planted as two rows spaced 40 cm apart between each row of cane. Sorghum (Sorghum vulgare) and maize (Zea mays) were planted along the side of the experiment to act as non-N₂-fixing reference plants for the application of the ¹⁵N natural abundance technique to quantify the BNF input to the legumes and the sugar cane. The soil cover, monitored using an overhead digital camera, showed that Crotalaria juncea was the quickest to establish and cover the soil. At 31 days after planting (DAP) it reached a height of over 60 cm, more than twice that of any of the other green manures, and covered 55% of the soil, 16% more than that of the second most vigorous legume, Canavalia ensiformis. Using the natural abundance ¹⁵N technique it was deduced that all of the legumes had obtained over 60% of their N from BNF. BNF inputs to some of the green-manure legumes were quite significant, ranging from 35 to 55 kg N ha^?1 for Canavalia ensiformis, Crotalaria juncea and Mucuna deeringiana at plant crop, whereas the effect of the presence of these legumes on final cane yield and dry matter and N accumulation was not significant. There was also considerable evidence of negative (allelopathic) effects on cane growth induced by the presence of some of the legumes, especially Crotalaria juncea.     

Changes in microbial biomass and protease activities of soil associated with long-term sugar cane monoculture

 As part of a broader study, the aim of which is to identify soil factors that might be associated with yield decline of sugar cane, microbial biomass and protease activities were examined in soil samples collected from seven paired old and new land sites in three cane-growing districts of north Queensland. No consistent changes in soil protease activities were observed, although some sites exhibited specific effects, as a result of extensive periods of sugar cane monoculture. Soil microbial biomass, however, was significantly lower in those soils where sugar cane had been grown for extended periods. The implications of a lowering of soil microbial biomass on sugar cane yields and sustainability are discussed. Received: 24 June 1997     

A headspace solid-phase microextraction method for the determination of some secondary compounds of Brazilian sugar cane spirits by gas chromatography

A headspace solid-phase microextraction (SPME) method was developed for the determination of secondary compounds from Brazilian sugar cane spirits, or cacha?a, by GC-FID. An SPME holder with an 85 microm polyacrylate coating was utilized. The novel method is compared with an optimized method: liquid-liquid extraction (LLE). Both methods showed good linearity, but the repeatability for analyses done with the SPME technique (%RSD = 1.8-3.9) was better than for those done with LLE (%RSD = 10.3-11.7). The concentrations of the analytes obtained in the analysis of 12 cacha?a samples with the SPME technique were higher than those obtained with LLE. In the SPME method the extraction wastes are smaller. Cacha?a samples were qualitatively analyzed for GC-MS.     

Comparison of the concentrations of phenolic constituents in cane sugar manufacturing products with their antioxidant activities

Polyphenol content and free radical scavenging capacity of seven kinds of sugar manufacturing products (A sugars, clear juices, syrups, massecuite, and A, B, and C molasses) were studied. Seventy-two samples were collected at different stages of the process during two sugar harvests from a local sugar factory (Bois-Rouge, La Réunion). The total phenolic content of sugar products was determined according to the Folin-Ciocalteu assay. Polyphenols of sugar products were extracted with ethyl acetate and quantified by LC-UV-ESI-MS during all of the process. ABTS and DPPH assays were applied to aqueous solution of sugar products, which exhibited interesting free radical scavenging activity. Comparatively, ethyl acetate extracts exhibited higher antioxidant activity. Multivariate analyses (principal component analysis and canonical discriminant analysis) demonstrated a significant correlation between polyphenols and antioxidant activity. Moreover, it was observed that the sugar process results in an increase of the phenolic content and the free radical scavenging capacity of the different products. These products and especially molasses proved to be a rich source of natural antioxidants and may represent an interesting alternative to synthetic food antioxidants.     

Efficiency of enzymatic and other alternative clarification and fining treatments on turbidity and haze in cherry juice

Several alternative strategies were examined for improving conventional juice fining procedures for cherry juice clarification and fining in laboratory-scale experiments: Centrifugation of freshly pressed juice from 1000g to 35,000g induced decreased turbidity according to a steep, negative power function. Individual and interactive effects on turbidity and haze formation in precentrifuged and uncentrifuged cherry juice of treatments with pectinase, acid protease, bromelain, gallic acid, and gelatin-silica sol were investigated in a factorial experimental design with 32 different parameter combinations. Gelatin-silica sol consistently had the best effect on juice clarity. Centrifugation of cherry juice (10,000g for 15 min) prior to clarification treatment significantly improved juice clarity and diminished the rate of haze formation during cold storage of juice. Both treatment of precentrifuged cherry juice with Novozym 89L protease and co-addition of pectinase and gallic acid improved cherry juice clarity and diminished haze levels. None of the alternative treatments produced the unwieldy colloids notorious to gelatin-silica sol treatment. The data suggest that several alternative clarification strategies deserve further consideration in large-scale cherry juice processing. Precentrifugation of juice before clarification and fining is immediately recommended.     

Changes in soil fertility and leaf nutrient concentration at a sugar cane plantation in Papua New Guinea

Abstract

Commercial sugar cane (Saccharum qfficinarum) cultivation in Papua New Guinea started in 1979 at a plantation in the Ramu valley where Udifluvents and Hapluderts are the dominant soil types. The sugar cane is not irrigated and receives only nitrogen (N) fertilizers (±90 kg N ha^‐1 y^‐1). Changes in soil chemical fertility were assessed by comparing soil fertility data from the mid‐1980s and 1990s and by comparing soil fertility data from sugar cane and adjoining natural grassland. Between the mid‐1980s and 1990s the topsoil pH had declined significantly (p<0.001) by 0.3 units and this was accompanied by a decline in cation exchange capacity (CEC) of 34 mmol_c kg^‐1. Total N levels in the topsoils declined (p<0.001) from 2.5 to 1.9 g kg^‐1 and available P from 36 to 27 mg kg^‐1 during the same period. Exchangeable potassium (K) also declined significantly (p<0.05) with 1.3 mmol_c kg^‐1, but changes in exchangeable calcium (Ca) and magnesium (Mg) were not significant. The decline in soil fertility was highest in the topsoil although significant changes occurred up to 0.6 m depth. Total N decreased in the 0–0.15 and 0.15–0.30 m soil horizons, but increased in the lower horizons, possibly because of nitrate leaching. A similar degree of soil fertility decline was observed when soils under sugar cane and adjoining natural grassland were compared. However, the interrow had a slightly lower fertility level in comparison to within sugar cane rows. The decrease in total N, available phosphorus (P) and exchangeable K in the soil coincided with a decrease in the leaf N, P, and K concentrations of the sugar cane over the past 10 years. It was concluded that soil fertility had markedly declined under sugar cane monocropping although levels remained favorable for sugar cane cultivation. For sustainable soil management, nutrient inputs as well as small applications of lime may eventually be needed.     

Sodium‐induced calcium deficiency in sugar beet during substitution of potassium by sodium

Functions of sodium (Na⁺) and potassium (K⁺) are closely associated. In some crops, Na⁺ is able to prevent or reduce considerably the occurrence of K⁺ deficiency. Sugar beet (Beta vulgaris L.) is a natrophilic crop, and positive effects of Na⁺ applications on yield were observed when K⁺ was sufficiently supplied. However, it is not known which specific function of K⁺ can limit the growth of sugar beet when K⁺ is substituted by an equivalent amount of Na⁺. Therefore, K⁺ substitution by Na⁺ was investigated for sugar beet in hydroponics. Surprisingly, no K⁺‐deficiency symptoms were observed. However, calcium (Ca²⁺) concentrations in the leaves were significantly decreased. Moreover, Ca²⁺ uptake and translocation through xylem sap were reduced in Na⁺‐treated plants. It is concluded that Ca²⁺ uptake by roots and its translocation via xylem sap primarily limit the possibility of K⁺ substitution by Na⁺ in sugar beet nutrition.     

Citrus juice extraction systems: effect on chemical composition and antioxidant activity of clementine juice

Clementines are especially appreciated for their delicious flavor, and recent years have seen a great increase in the consumption of clementine juice. In previous decades, antioxidant compounds have received particular attention because of widely demonstrated beneficial health effects. In this work, the organoleptic, volatile flavor, and antioxidant quality of clementine juice were studied with regard to the influence on them by different juice extraction systems: plug inside fruit and rotating cylinders. The results showed that juice extracted by the former method presented higher yields and hesperidin content, which was related to higher antioxidant activity, demonstrated by ORAC and LDL assays. The organoleptic quality was not affected by the processing technique, whereas there were significant differences in the chemical flavor profile. There are important differences in chemical and functional quality between juice extraction techniques, which must be taken into account when employing processing systems to produce high-quality products.     

Relationship between nutrient element content of the index leaf and cane yield and juice quality of sugarcane genotypes

Abstract

The nitrogen (N), phosphorus (P), potassium (K), iron (Fe), manganese (Mn), zinc (Zn), and copper (Cu) content of the index leaf (whole third leaf) of eleven genotypes of sugarcane [Co 7717, CoJ 64, CoP 84211, CoH 92, and CoH 99 (early maturing); CoS 767, CoH 3, and CoH 108 (mid maturing); and Co 1148, CoH 35, and CoLK 8102 (late maturing)] were determined at the maximum growth stage of the crop. The elemental contents were correlated with cane yield and juice quality parameters [% sucrose, % commercial cane sugar (CCS), and sugar yield] at harvest. The N, P, K, Fe, Mn, Zn, and Cu contents of the third whole leaf for all eleven genotypes ranged (mean in parenthesis) from 1.46–1.80 (1.62), 0.20–0.37(0.30), 1.39–1.88 (1.67)%, and 376–1095 (613), 58–155 (98), 53–99 (74), and 8–14 (11.5) ugg¹ of dry weight, respectively. Among the eleven genotypes, CoJ 64 had lowest N, P, and K contents in their index leaves as well as the lowest cane yield, % sucrose, and sugar yield, whereas CoH 35 had highest, followed by CoH 108 for these parameters. The leaf N, P, and K contents showed significant linear positive correlations with cane yield (r=0.84, 0.79, and 0.87, respectively), % sucrose (r=0.70, 0.68, and 0.65, respectively), and sugar yield (r=0.89, 0.81 and 0.90, respectively). Among the micronutrients, leaf Cu had a linear positive correlation (r=0.61) with cane yield. The multiple regression of cane yield with N, P, K, Zn, and Cu explained 93% of the variation, whereas the multiple regression of % sucrose and % CCS with N, P, and K leaf content and sugar yield with N, P, K, and Cu explained 82%, 84%, and 95% of the variation, respectively.