Effect of processing on post-bottling haze formation in apple juice

Post-bottling haze formation in clarified apple juice produced under a variety of processing conditions was studied. Turbidity of the juice was monitored at intervals during a 6-month storage period. Changing the pasteurization temperature of raw juice and omitting the addition of amyloglucosidase did not retard or prevent haze development. Omission of the fining procedure, however, resulted in an increase in turbidity of 1.36 NTU and visual observation of larger quantities of haze. Fining with a gelatin/bentonite ratio of 1:1 gave the least haze. Thermocoagulation treatment applied to the juice prior to ultrafiltration also did not retard or prevent haze formation. Ultrafiltration at lower processing temperatures resulted in the development of less haze. At higher temperatures an increase in turbidity of over 14 NTU was observed. The results suggest that optimization of the fining procedure and ultrafiltration could be used to retard post-bottling haze in apple juice.     

Color Stability of Apple and Pear Juices Blended with Fruit Juices Containing Anthocyanins

Apple and pear juices blended with anthocyanin pigmented juices developed haze and color stability during commercial marketing. To determine factors contributing to these problems, juice from apple and d'Anjou pear (prepared from whole fruit) and‘Bartlett’pear (peels and cores) were blended with 5, 10, 20%‘Concord’grape,‘Bing’cherry, or red or black raspberry juice. During storage at 25°C for up to 48 wk, turbidity, polymeric color, and % color due to tannin increased, while anthocyanin concentration decreased. As % anthocyanin pigmented juice increased, turbidity and polymeric color increased and % color due to tannin decreased. Within a given base juice, turbidity was highly correlated with polymeric color (r = 0.78 to 0.97).     

Effect of ultrafiltration on concentrated apple juice colour and turbidity

Colour and turbidity of conventional bentonite-gelatin clarified apple juice was compared with 30,000–50,000 and 100,000DA hollow fibre ultrafiltered apple juice, with and without pectinolytic enzyme treatment. Results indicated that objective quality of ultrafiltered apple juice compared favourably with conventionally clarified apple juice over 30 weeks of storage at 37.5°C. However, treatment with pectinolytic enzymes before ultrafiltration increased both the initial colour and the browning rate. No significant differences were found in the values of the transmission haze after storage.     

热协同超高压处理对含防褐变剂鲜榨苹果汁贮藏品质的影响

采用HPLC等分析方法研究了400MPa单独处理,50℃协同300MPa处理和50℃单独处理对含防褐变剂鲜榨苹果汁在4℃贮藏时品质的影响。研究发现:经过45d的贮藏,仅经过400MPa压力处理的和仅经过50℃处理的果汁中酚类物质含量比经过50℃协同300MPa处理的含量低,差异显著(P<0.05)。50℃协同300MPa处理还可显著降低果汁中微生物数目,同时果汁在贮藏期内的L值和a值均优于其他2种样品。50℃协同300MPa处理鲜榨苹果汁的可溶性固形物含量和pH值贮藏前后没有显著差异(P>0.05)。经过贮藏,所有样品中的总VC的保留率>95%。     

Kinetics of haze formation and factors influencing the development of haze in clarified apple juice

The rate of haze formation in commercial clarified apple juice stored at 4, 25 and 37°C was monitored over a 16 to 35-week storage period. Changes in turbidity, tannin content and browning index were evaluated. The juice appeared virtually clear and had very little colloidal particles during the initial stages of storage. After 24 weeks, an increase in turbidity of 2.32 NTU was observed for juice samples stored at 37°C. An increase of 0.58 and 0.95 NTU was observed for samples stored at 25 and 4°C, respectively. There was a general decrease in tannin content and an increase in browning index with storage; this effect was most pronounced for samples stored at 37°C. The rate of haze formation and tannin depletion in juice samples followed first-order reaction kinetics. Light and headspace did not affect haze formation. NaCl and CaCl₂ increased haze development while sucrose (up to 60%), urea (0.5 M), and EDTA (up to 0.01 M) had little effect. Addition of sodium dodecyl sulfate retarded haze formation.     

Effects of moderate electrothermal treatments on juice yield from cellular tissue

Ohmic and microwave heating were employed to investigate electro-thermal effects on apple juice yield by preheating apple samples to 40 or 50 °C. Cylindrical raw and pretreated samples from fresh apple were wrapped in a non-absorbent cloth and pressed to produce juice. Data on juice yield and applied force were recorded and compared with the raw material. The results showed that apple juice yield was strongly improved by both thermal pretreatments, and pretreated samples showed less resistance during extraction. The thermal effect of ohmic pretreatment on juice yield increased with the pretreatment temperature, while for microwave pretreatment, the low pretreatment temperature resulted in high juice yield. Ohmic heating as a pretreatment increased juice yield and required less input work, compared to microwave heating; thus frequency might play a major role in this effect. The thermal effect difference could be due to increased migration of cellular moisture during ohmic pretreatment. These observations indicate ohmic pretreatment has the potential to enhance juice yield and save energy.     

Maturity and ripening effects on chemical and sensory properties of apple juice

The effects of harvest maturity and ripening on the chemical composition and sensory characteristics of ‘McIntosh’ and ‘Spartan’ apple juice were evaluated. Juice was extracted from fruit harvested at seven weekly intervals beginning 3–4 weeks before commercial harvest and from fruit held in air storage (1°C) for 1 to 3 months. Internal ethylene concentration and starch index were used as maturity indices. Principal component analysis of juice data (pH. titratable acidity, organic acids, soluble solids, sugars, phenols, turbidity, and Hunterlab colour) showed a distinctive maturity effect on the characteristics of juice extracted from fruit immediately after harvest or after storage. Triangle testing showed aroma and flavour differences in both ‘McIntosh’ and ‘Spartan’ to be first discernable when ethylene was first detected (internal ethylene concentration ≥ 0.1 μl litre^?1) and starch hydrolysis evident (starch index 3.0–5.0 for ‘McIntosh’, 1.5–3.0 for ‘Spartan’), or after 2–3 months of air storage. Sensory profiling of fruity aroma, total aroma, fruit flavour by mouth, sweetness, and sourness in the juices showed increased fruitiness and sweetness and decreased sourness with advancing maturity.     

贮藏和包装条件对苹果浓缩汁二次混浊形成的影响

本文研究了贮藏和包装条件对二次混浊物形成的影响.通过测定果汁的浊度以及与二次混浊有关的酚类和蛋白质的变化,阐明贮藏和包装条件对二次混浊形成的影响.二次混浊果汁的浊度及缩合单宁的含量随贮藏时间的延长和贮藏温度的升高而增加,小分子的酚类以及可溶性蛋白质的含量随贮藏时间的延长和贮藏温度升高而减少.贮藏期间二次混浊形成的浊度变化遵循一级反应方程.二次混浊现象随包装顶隙的增加而加重,用BOPP膜包装的果汁二次混浊比玻璃瓶和铝箔包装的严重,光照对果汁二次混浊的形成无影响.短时间或低温贮藏条件以及选择透氧率低的包装材料会减少二次混浊的形成.     

Xyloglucan endotransglycosylase activity in apples is ripening-related: implications for fruit juice processing

In order to assess the role of endogenous enzymes during apple juice manufacturing by enzymic liquefaction, apples of different maturity were assayed for various enzyme activities. Xyloglucan endotransglycosylase (XET) activity increased dramatically from early September to mid October, and decreased slowly during cold storage. It was shown that XET is probably the most important, endo-acting activity in apple. The apples of different maturity were also treated by pectin lyase and various concentrations of cellulase. It appeared that less cellulase was needed for disintegration of apples with a high level of XET activity. This suggests that XET facilitates the liquefaction process. Under certain conditions, ‘high XET’ apples could be transformed into a cloudy apple juice. This cloud may be regarded as a dispersion of particles which is predominantly composed of cellulose and xyloglucan. © 1998 Society of Chemical Industry.     

活性炭对苹果汁中多酚和混浊物的吸附研究

利用苹果汁工业化生产线上取样 ,采用香草醛 盐酸法、正丁醇 盐酸法以及液相色谱测定多酚 ,用浊度仪测定混浊程度 ,研究了活性炭吸附对苹果汁中的多酚和混浊的影响。结果表明 :活性炭吸附可减轻混浊 ,减少后混浊的前体物质及缩合单宁含量 ,减少活性蛋白的含量     

Efficacy of phytic acid as an inhibitor of enzymatic and non-enzymatic browning in apple juice

Browning decreases the commercial value of apple juice, and therefore colour preservation during processing and storage is the main objective of manufacturers. In this study, the efficacy of phytic acid as a browning inhibitor for use on apple juice was investigated. Browning of apple juice treated with phytic acid was monitored during processing and storage. 0.1 mM Phytic acid inhibited the polyphenol oxidase (PPO) from the apple juice by 99.2%. Consequently, the apple juice treated with phytic acid had significantly lower browning formation during processing and after 6 months of storage at room temperature compared with the control (p<0.05). Results indicate that this is a promising way to inhibit browning in apple juice.     

多酚和蛋白质对苹果浓缩汁浊度的影响

用从苹果浓缩汁中提取的蛋白质,加入单宁酸建立模拟体系,测定浊度,并通过响应曲面分析了单宁酸和蛋白质对苹果汁浊度的影响,结果表明,苹果汁中单宁酸与浊度的关系是线性增加的,蛋白质与浊度的关系则是先上升后下降,蛋白质浓度为25mg/L时产生的浊度最大。     

Flavour losses in apple juice manufacture

Flavour losses occurring in apple juice manufacture were investigated by gas chromatography and sensory analysis in two factories A and B using different technologies and equipment. Samples were taken at different intervals during the processing season from the raw material, the pressed juice, the clarified and filtered juice, the apple juice concentrate and the apple flavour concentrate produced in plant A. The chromatograms of the pressed juice showed changes in volatile composition as compared to the raw material: the number of components was slightly reduced, although some new components could be detected, probably owing to enzymatic processes. The enzyme preparation and method used for clarification did not affect volatile composition to the extent expected. The volatile abstracting effect of vacuum evaporation for flavour recovery as performed in plant A seems to be compensated by flavour formation from precursors during pectolytic enzyme treatment. The greatest losses in both factories were encountered during evaporation concentration of the clarified and filtered juice. Chromatographically established volatile composition was distinctly different in the concentrated apple juice samples from the two plants, however, this difference was perceived by the sensory test panel only towards the end of the processing season. The apple flavour concentrate contained less than half of the volatile components present in the raw material. The gas chromatograms of the flavour concentrates produced at different times did not reflect the fluctuations observed in the volatile composition of the raw material and the intermediate and end products, however, sensory tests showed the samples from the beginning of the processing season to be superior to those from its end.     

Fumaric acid in apple juice: a potential indicator of microbial spoilage of apples used as raw material.

The effects of heat treatment (evaporation and excessive heating), and microbial contamination (Rhizopus stolonifer, Penicillium expansum and Lactobacillus plantarum) as sources of fumaric acid formation in apple juice concentrates were investigated. Fumaric acid formed in apple juice did not exceed 1.0 mg l(-1) during both commercial-scale evaporation and laboratory-scale excessive heat treatment, indicating that malic dehydration is not the primary source of fumaric acid formation. However, R. stolonifer and L. plantarum produced 18.23 +/- 0.82 and 5.39 +/- 0.31 mg l(-1) fumaric acid as determined in the raw juice obtained from contaminated apples after 5 days of incubation. The mean fumaric acid content of apple juice concentrates manufactured in 2000, 2001 and 2002 were determined as 4.9 +/- 1.9, 5.7 +/- 2.8 and 4.1 +/- 2.6 mg l(-1), respectively. The overall results suggest that the primary source of fumaric acid in apple juice concentrate is the use of apples decayed by certain microorganisms capable of producing fumaric acid.     

不同品种苹果冷藏期间品质与生理变化

研究贮藏期间果实品质生理变化,探讨不同优质苹果品种的贮藏特性。以‘岳帅’、‘望山红’、‘岳阳红’、‘秋富红’苹果为试验试材,在温度（0±0.5）℃、相对湿度90%～95%冷库内贮藏,定期测定果实呼吸强度、硬度、可溶性固形物含量、可滴定酸含量、VC含量、果实质量损失率、多酚氧化酶活性、过氧化物酶活性,分析果实生理品质指标变化与贮藏特性的关系。结果表明,‘岳帅’苹果呼吸强度及酶活性较低,但呼吸高峰出现早,贮藏84 d后果实品质劣变迅速;‘岳阳红’苹果呼吸强度和酶活性较低,贮藏期间果实品质、风味保持最好;‘望山红’和‘秋富红’苹果呼吸高峰出现最晚,果实品质保持较好。通过理化指标和感官评价比较得出：‘岳帅’贮藏期较短,不宜超过84 d;‘岳阳红’、‘望山红’和‘秋富红’苹果适宜长期贮藏,其中‘岳阳红’苹果在贮藏过程中品质及营养成分损失最少,贮藏期可达180 d以上。     

Polyphenol content and antioxidative activity in apple purées with rhubarb juice supplement

The purpose of the present study was to evaluate the effect of rhubarb juice addition and peeling in apple purée production and storage on its phenolic composition, antioxidant activity and colour. The apple material used in this study was of two varieties: Sampion and Idared. The apple purées prepared in three variants (control purées, peeling purées and purées with 5% of rhubarb juice) were stored for 3 and 6 months at 30 °C. Apple purées were investigated for their antioxidant activity, change of colour and contents of phenolic compounds plus the polymer procyanidins and degree of polymerization (DP). The preparation of purées from apples without peeling and the addition of rhubarb juice during purée preparation had significant influence on polyphenol content. The purée prepared from peeled apples of Idared variety had phenolic content 2.2 times lower than the control sample (non‐peeled apples). The highest level of total polyphenols was found in Idared + rhubarb sample (129.82 mg 100 g^?1 purée). The content of this compound in Idared control sample was more than 2.8 times lower than in Idared purées with rhubarb. The use of non‐peeled Idared apples and 5% of rhubarb juice in purée preparation significantly increased polymeric procyanidins from 11.68 to 75.20 mg 100 g^?1 and other phenolics from 9.23 to 54.62 mg/100 g. This effect for Sampion apples was smaller. The procyanidins during purées storage were more stable in samples with rhubarb juice addition. The purée samples with the addition of rhubarb juice had higher antioxidant activity measured using ABTS (2,2′azinobis‐(3‐ethylbenzthiazoline‐6‐sulphonic acid)) than purée samples without the addition (two times higher for Idared variety) of rhubarb juice. After 3 and 6 months of storage at temperature 30 °C, the antioxidant capacity decreased in all purées. Rhubarb juice had only high and positive effect on L* value in the case of Idared variety. The results showed that all Sampion apple purées had higher L* values than Idared.     

Haze and cloud in apple juices

Turbidity in apple juice is desirable or undesirable, depending on whether the product fits within consumer expectations. Desirable opalescence is due to soluble pectin and insoluble pectin stabilized particles that show considerable stability. Blanching treatments enhance this stability by reducing particle size and character‐solubilizing pectin, and possibly by the destruction of natural enzymes that may destabilize the cloud over time. Undesirable haze and sediments may arise in apple juice by several mechanisms, including starch (dextrin) retrogradation, protein phenol aggregation, phenol oxidation, crystallization of carbohydrate macromolecules extracted from cell walls, or difficulties during manufacture. The mechanisms of formation of each of these forms of haze are discussed and examples given from the literature. Where available, haze‐sediment morphology by light and/or electron microscopy is documented and the possible role of recently developed “macerase” enzymes in haze/sediment formation discussed.     

浓缩苹果汁多糖对浊度的影响

采用醇沉法从浓缩苹果汁中提取多糖,HPLC测得苹果汁多糖由葡萄糖、果糖、阿拉伯糖组成,阿拉伯糖和葡萄糖聚合参与混浊的形成。建立多糖-蛋白质模拟体系(pH3.7的磷酸钠缓冲溶液)发现,浊度随着多糖和蛋白质浓度的增加呈上升趋势,多糖能降低蛋白质-单宁酸聚合产生的浊度。     

Haze-Active Protein and Polyphenols in Apple Juice Assessed by Turbidimetry

The amount of haze-active protein in apple juice was determined by adding tannic acid to induce haze followed by turbidimetry. Turbidity was essentially linear with protein concentration. PVPP treatment prior to tannic acid addition appeared to remove endogenous polyphenols and resulted in slightly weaker response. Adding gelatin to apple juices or clarified ciders induced hazes in response to content of haze-active polyphenols. At an appropriate gelatin concentration turbidity was nearly linear with polyphenol concentration. Treatment with bentonite prior to gelatin addition appeared to remove endogenous protein. Temperature control during the induction period was critical to reproducibility.     

加工过程对NFC苹果浊汁营养品质的影响

NFC(非浓缩还原)果汁因其丰富的营养而受到普遍关注。以国光苹果为原料,经打浆、酶解、过滤和杀菌等工艺环节制备NFC苹果浊汁,探讨主要加工环节对苹果浊汁营养品质的影响。结果表明:加工过程中苹果浊汁可溶性糖和还原糖逐渐上升;可溶性蛋白以及果胶含量逐渐下降;可溶性固形物、多酚以及黄酮含量呈先升高后下降的趋势。苹果浊汁加工过程中,多项营养指标间的变化显著相关。酶解过程对可溶性蛋白和可溶性果胶影响较大;过滤过程对蛋白、果胶、黄酮等颗粒构成物的影响较大;杀菌过程使总酚、黄酮等生物活性物质明显减少。旨在为NFC苹果浊汁加工过程中营养素的保持提供理论借鉴,为国光苹果的加工技术应用奠定理论基础。