Optimization of Carrot Juice Color and Cloud Stability

Investigations were conducted on the effects of heating, acidification, and enzyme treatment on carrot juice color and cloud stability. Heating whole carrots to 93°C prior to milling and pressing improved juice color, but reduced juice yield compared to heating milled carrots to 93°C. Juice color was improved by acidification of milled carrots to pH 5 or 4 with citric acid prior to pressing. Juice from carrots heated before milling clarified quickly if not acidified before pressing. Acidification after juice extraction did not stabilize cloud. A commercial pectinase/hemicellulase preparation improved juice color, but not juice yield. Only 20% of potential β-carotene was extracted from carrots during pressing, and β-carotene was extracted to a greater extent than α-carotene.     

EFFECT OF SOLUBLE SOLIDS AND TEMPERATURE ON ASCORBIC ACID DEGRADATION IN LEMON JUICE STORED IN GLASS BOTTLES

Lemon juice at concentrations of 9°, 20°, 30°, 40° and 50°Brix was stored at 10°, 20° and 36°C for 16 weeks and sampled regularly for total soluble solids (TSS), pH, titratable acidity and ascorbic acid. No significant differences were found in the first two of these factors as a function of storage time. There was a small but significant decrease in citric acid concentration over 16 weeks. Ascorbic acid loss was greater at higher temperatures; at a constant temperature, the loss was smaller as TSS increased. Ascorbic acid degradation data fitted zero-, first- and second-order models equally well at all five TSS. Rate constants in 9°Brix juice were significantly higher than those for the other four concentrations at all three temperatures. E_a values of 47.8 and 24.1 kJ mol^?1 were calculated for ascorbic acid degradation in 9° and 20°Brix juices. The effect of temperature far outweighed the effect of TSS on ascorbic acid degradation. Over the 16-week storage period, maximum retention of ascorbic acid (95.7%) was obtained in the 50°Brix lemon juice concentrate stored at 10°C.     

Citric Acid and Antimicrobials Affect Microbiological Stability and Quality of Tomato Juice

Acidification, addition of dimethyl dicarbonate and a mixture of potassium sorbate and sodium benzoate and storage temperature were related to microbiological stability and quality of tomato juice. Whether iuices were acidified CDH 4.0 to 3.7) or nonacidified. dimethyl dicarbonate and sorbate/benzoate were highly effective in diminishcng mold and yeast count at 5°C and 20°C. Dimethyl dicarbonate in juices acidified to pH 3.7 and stored at 5°C was most effective in controlling plate counts, followed by sorbate/benzoate in juices acidified to pH 3.7 and stored at 5°C and 20°C. Tomato juice treated with dimethyl dicarbonate had lower amounts of ascorbic acid, total amino acids, fructose, glucose, lycopene and β-carotene.     

Non‐freezing points below zero induce low‐temperature breakdown of kiwifruit at harvest

To induce low‐temperature breakdown (LTB) at harvest, a post‐storage disorder of kiwifruit, kiwifruit were exposed to ?2 °C (a temperature determined to be above the freezing point), for 0 (control), 6, 12, 18, 24, 30, 36 and 42 h, followed by 5 days at 20 °C. Kiwifruit were also stored at ?0.5 °C for 16 and 24 weeks plus 5 days at 20 °C. LTB incidence and severity were measured on the cut surfaces following slicing at the upper, middle and lower parts of each fruit subjected to ?2 °C, whereas in stored fruit LTB incidence was measured following slicing at the middle part. Electrolyte leakage (ELL) was also determined. Exposure of fruit to ?2 °C resulted in induction of LTB incidence and severity, which increased with the duration of exposure, particularly, on the upper fruit part. Maximum ELL during exposure at ?2 °C for 36 h or during storage at ?0.5 °C for 16 weeks was as high as 50% of that of the frozen fruit. Fruit exposed to ?2 °C or stored at ?0.5 °C had similar LTB symptoms but both differed from those observed in frozen fruit. LTB of fruit stored at ?0.5 °C for 24 weeks was 27% and corresponded to LTB induced at harvest by exposure at ?2 °C for 24 h. The results of this study confirm that LTB is inducible by low but not freezing temperatures at harvest and therefore it might be considered as the physiological basis towards the development of an LTB incidence index for harvested kiwifruit. Copyright © 2006 Society of Chemical Industry     

Kinetics of anthocyanin degradation and polymeric colour formation in black carrot juice concentrates during storage

The changes in anthocyanins (ACNs) and polymeric colour of black carrot juice concentrate (BCJC) samples were monitored during storage at ?23, 5 and 20 °C for 319 days and at 30 °C for 53 days. While ACN degradation was fitted to a first‐order reaction model, polymeric colour formation was fitted to a zero‐order reaction model during the storage. Half‐life periods for ACN degradation in BCJCs were 603, 137 and 29 days at 5, 20 and 30 °C, respectively. The reaction rate constants for polymeric colour formation were 0.0207, 0.1435 and 0.5581%/days at 5, 20 and 30 °C, respectively. HPLC‐MS analyses of BCJC showed that cyanidin‐3‐galactoside‐xyloside‐glucoside‐ferulic acid (56%) was the major ACN, followed by cyanidin‐3‐galactoside‐xyloside (19%) and cyanidin‐3‐galactoside‐xyloside‐glucoside‐sinapic acid (10%). Cyanidin‐3‐galactoside‐xyloside‐glucoside‐ferulic acid was the most stable ACN in BCJC at storage temperatures. BCJCs should be kept at sub‐freezing temperatures to minimise ACN degradation.     

Synbiotic potential of carrot juice supplemented with Lactobacillus spp. and inulin or fructooligosaccharides

BACKGROUND: The influence of the addition of two probiotic strains, Lactobacillus rhamnosus and Lactobacillus bulgaricus, and the prebiotic components inulin and fructooligosaccharides on carrot juice was investigated in order to evaluate the possibility of producing a functional vegetal beverage. RESULTS: Both bacterial strains were capable of growing in carrot juice, reaching nearly 5 × 10⁹ colony‐forming units after a 48 h fermentation, and the pH was reduced to 3.5–3.7 or below. The viable cell counts of the two lactobacilli in the fermented juice after 4 weeks of storage at 4 °C, demonstrated good survival of the two strains at low pH. Some biochemical characteristics of the fermented juice, such as β‐carotene content and antioxidant activity, were also preserved, indicating that the metabolism of the Lactobacillus spp. did not degrade these nutritional components after 4 weeks of storage at 4 °C. The positive effect was more evident when the juice was inoculated with Lactobacillus rhamnosus. The presence of inulin and fructooligosaccharides did not alter the cell counts or the biochemical characteristics of the fermented juice. CONCLUSION: We propose this as a health juice and functional beverage for vegetarians or consumers who are allergic to dairy products. Copyright © 2008 Society of Chemical Industry     

Microbial and enzymatic changes in natural soursop puree during storage

Microbial and enzymatic comparisons were made on natural soursop puree stored at 15, 4 and −20°C without pasteurisation and with pasteurisation at 79°C for 69 s. Results showed that pasteurisation caused significant decrease in microbial count in soursop puree from 6.4×10³ to 8.5×10¹ cfu per g. Generally, storage at −20°C exhibited greater stability of samples as compared to those kept at 4 and 15°C. In contrast to microbial reduction, pasteurisation caused significant increase in cloud from 0.318 to 0.529 and completely inactivated the pectinesterase enzyme. The puree packed into foils kept at 4°C exhibited decreased cloud loss as compared to others packed in cans and bottles kept at 15 and −20°C. No pectinesterase enzyme regeneration was observed for pasteurised puree in this study during 12 weeks of storage time.     

Use of Acidification, Low Temperature, and Sorbates for Storage of Orange Juice

The effects of acidification, combination of acidification and low temperature and sorbates on the storage of orange juice were investigated. Acidification of orange juice to pH 2.0 and pH 2.5 followed by storage at 5°C resulted in marked reduction in total plate count and yeast and mold population during twelve weeks of storage. Use of 0.03% sorbic acid or potassium sorbate in combination with acidification at pH 2.5 resulted in preservation of orange juice stored at 10°C over 10 wk period; however, vitamin C degradation was enhanced by the presence of the sorbates. The results also indicated that relatively high concentrations of vitamin C were present in orange juice containing high population of microorganisms.     

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.     

Quality changes of frozen vegetables

Unblanched and blanched vegetables (carrot, cauliflower, French bean, onion, leek and swede) were stored at ?20°C and ?30°C for up to 15 months. Lipid and peroxidase analyses and sensory evaluations were performed every three months.Unblanched leek, onion and swede did not change appreciably during the 15 months' storage, either chemically or organoleptically, and they were scored better than the blanched samples. Carrot, cauliflower and French bean, on the other hand, had to be blanched, but a 5% residual activity of peroxidase did not affect the quality during storage.     

A Functional Smoothie from Carrots with Induced Enhanced Phenolic Content

Carrots are worldwide highly consumed due to their sensory characteristics and health-promoting properties. However, their low phenolic/antioxidant levels may be highly increased with abiotic stresses. Accordingly, phenolic/antioxidant enhancements and related phenylalanine ammonia-lyase (PAL) activity of carrot shreds under different treatments (UV-C radiation and hyperoxia conditions) were studied after a pre-enrichment incubation of 72 h at 15 °C. Subsequently, a carrot smoothie prepared from enriched carrot shreds was heat-treated (90 °C for 30 s) and stored at 5 °C up to 14 days. Heat-treated smoothies showed a good physicochemical and microbiological quality (<6 log CFU g^?1) after 14 days at 5 °C, although those non-irradiated samples registered lower psychrophilic and yeast and mold levels. Heat-treated smoothie from non-irradiated shreds stored under hyperoxia conditions showed the highest total phenolic content of 13.82 mg chlorogenic acid equivalent (ChAE) kg^?1 fw (87 % chlorogenic acid) after 14 days at 5 °C. Total phenolic content was in accordance with PAL and total antioxidant capacity. Conclusively, a pre-enrichment incubation of carrot shreds under hyperoxia conditions allowed to obtain a functional smoothie with high phenolic levels and good microbiological and physicochemical quality up to 14 days at 5 °C.     

Effects of Selected Commercial Phosphate Products on the Natural Bacterial Flora of a Cooked Meat System

Four commercial phosphate blends and a neutral pyrophosphate were used at three levels (0.30–0.65%) in the preparation of cooked sausage. Control treatments contained no phosphate. Vacuum-packaged sausage was stored at 5°C for 21 days or held at room temperature (20–22°C) for up to 48 hours after 7 days of refrigerated storage. Mesophilic and facultative anaerobic bacterial counts were highest in control treatments after 14 and 21 days at 5°C and after 24 and 48 hr at 20–22°C. For each phosphate, the level of addition was the determining factor in bacterial inhibition, since the highest phosphate level resulted in the lowest bacterial counts in sausage held at 5°C and 20–22°C. The level of phosphate was more important in prolonging shelf life than was the type of phosphate.     

Effects of N6-Benzyladenine and Storage Temperature on Shelf-Life and Quality of Raw and Cooked Broccoli (Brassica oleracea L. var. italica)

Fresh broccoli heads were dipped in solutions containing 20 ppm N⁶-benzyladenine (BA) with 0.1% Tween-20 or water with 0.1% Tween-20 for 30 sec then stored for 5 wk at 2° and 5°C. Broccoli heads receiving BA treatments maintained higher subjective quality ratings for color, turgidity, aroma, flavor, and texture throughout the 5-wk period. Gardner color measurements and total chlorophyll were significantly higher for samples treated with BA and stored at 2°C than for controls. Samples stored at 2°C had lower shear resistance than those kept at 5°C. The content of hot water insoluble materials (fiber) was much less in broccoli heads treated with BA than in untreated heads. Maintenance of good quality by BA treatment and 2°C storage was reflected in all parameters of sensory evaluations for cooked broccoli. Loss of color and reduction of quality were observed in raw and cooked broccoli during 4 wk of storage. Evaluations of quality parameters and color measurements were greatly influenced by the turgidity factor.     

Effects of pH, Storage Time and Temperature on the Tin Content of Single Strength Canned Grapefruit Juice

Grapefruit juice modified to pH 3.0, 3.5 and 4.0 and stored at 4, 21, 27, 32 and 38°C manifested a consistent two-stage pattern for tin uptake. The first stage consisted of a rapid (3 wk) uptake of tin (from 12 to approximately 100 ppm) and was relatively independent of juice pH or storage temperature. In the second stage, the increase in tin concentrations was extremely temperature dependent and only slightly pH dependent. Canned grapefruit juice should be stored below 27°C to insure tin contents do not exceed the Codex maximum of 250 ppm. In a survey of 55 commercially canned grapefruit juice samples stored 1-8 months under commercial conditions, tin concentrations ranged from 34-180 ppm.     

Effects of thermosonication and orange by‐products extracts on quality attributes of carrot (Daucus carota) juice during storage

Effect of thermosonication on carrot juice containing peel (CJPL) and pulp (CJPP) extracts from orange at different concentration (0.5, 2.0 and 4.0 mg GAE per g extracts) of total phenolic contents (TPC) was evaluated for quality attributes. Thermosonication of juice was done at 52 °C, 6 min for CJPL and 60 °C, 5 min for CJPP (values based on our preliminary optimisation results of ultrasound process conditions of the juice) at 40 kHz and 110W. Effect of thermosonication and addition of peel and pulp extracts at highest concentration increased the TPC and antioxidant activity of the juice (P < 0.05). Highest inactivation of microorganisms and better sensory attributes was achieved in thermosonicated CJPP for 21 days. Titratable acidity, pH, browning index and viscosity were improved by thermosonication and at highest extract concentration. °Brix and total carotenoid were not significantly affected by treatments. Therefore, thermosonication at 60 °C and 4.0 mg GAE per g extract concentration of peel and pulp may be used in formulation of functional carrot juice with improved health properties.     

Storage of spinach juice agglomerates: Physical,flow, structural,and thermal properties

The objective of this study was to investigate how the various storage temperatures affected the physical properties, flow characteristics, microstructure, and glass transition temperature of spinach juice agglomerates. For this purpose, spray-dried spinach juice powders were processed to agglomerates by using a modified fluidized bed dryer (1.6 m/s airflow rate, 60°C drying air temperature, 20 min processing time, and with different binder solutions containing agents as maltodextrin, gum Arabic, and whey powder isolate). The analyses were carried out every month throughout 6 months while the spinach juice agglomerates were stored at temperatures of 4, 20, and 35°C. The results revealed that over the storage time, the moisture content and water activity values of the agglomerates were generally under 11% and 0.6, respectively. The color values generally showed a decreasing trend depending on the storage time. The solubility times of the samples stored at 4°C were longer than those of stored at other storage temperatures. The SJA-GA had the lowest HR and CI values and thus the best flowability properties during all storage times. There was no detectable change in the structures of SJA stored at 20°C according to the storage time. Throughout the storage time, it was discovered that the glass transition temperature of all spinach juice agglomerates was remarkably similar. Overall, the investigation revealed that storage at 35°C for 6 months might be suitable because it delivered the intended outcomes such as greater flowability and cohesiveness, and shorter wettability and solubility times.     

Influence of different storage conditions on changes in the key aroma compounds of orange juice reconstituted from concentrate

Quantification of aroma compounds in an orange juice reconstituted from concentrate which had been stored at 37 °C for 4 weeks (forced storage) revealed an increase in the concentrations of, in particular, dimethyl sulphide, 2-methoxy-4-vinylphenol, α-terpineol, and 4-hydroxy-2,5-dimethyl-3(2H)-furanone (4-HDF) in comparison with the same orange juice before storage. On the other hand, clearly lower concentrations were found for octanal, decanal, (R)-α-pinene, linalool, and (E)-β-damascenone after storage, while the concentrations of vanillin and carvone remained nearly constant. Similar results were found for the same aroma compounds after storage of the orange juice at 20 °C for 1 year. Sensory experiments corroborated the importance of 2-methoxy-4-vinylphenol and dimethyl sulphide for the typical stale off-flavour of the stored orange juice, while the omission of e.g., α-terpineol in model mixtures could not be detected. Under both storage conditions (37 °C for 4 weeks or 20 °C for 1 year), the breakthrough odour thresholds of α-terpineol and 4-HDF were not reached, while the concentrations of dimethyl sulphide and 2-methoxy-4-vinylphenol clearly exceeded their breakthrough odour thresholds, thus confirming the crucial role of these odorants for the off-flavour of stored orange juice from concentrate. In addition, changes in the concentrations of selected orange juice odorants at various temperatures and times were investigated.     

Storage Stability of Orange Juice Concentrate Packaged Aseptically

Orange juice concentrates were packaged aseptically by a “Dole” aseptic canning machine using 6 oz metal cans. The final juice products (11°, 34°, 44°, 58° Brix) were stored between ?18° and 36°C and tested periodically for nonenzymatic browning, ascorbic acid destruction, furfural and sensory changes. Nonenzymatic browning, the main deterioration phenomena in these products, was satisfactorily retarded at 12°C or lower. Ascorbic acid destruction rate constant was dependent on temperatures between 5 and 25°C, and was affected by degree of juice concentration. Furfural accumulation in juice was higher than that in 58° Brix concentrate. Orange juice concentrate of 58° Brix did not show flavor changes after storage at 5°C or 12°C for 17 or 10 months, respectively, when evaluated after reconstitution to 11° Brix.     

Isopropyl N-(3-chlorophenyl) Carbarmate (CIPC) Effect on Nitrogenous Constituents of Potatoes

Potatoes treated with 1% or 3% CIPC and stored 16 weeks at 5°C and 20°C were analyzed for nitrogenous constituents. Treatment with 1% CIPC significantly (p < 0.025) increased total nitrogen and protein content in tubers of two cultivars compared to untreated control tubers following storage at 5°C and 20°C. Treatment with 3% CIPC increased total nitrogen and decreased protein in tubers stored at 20°C (p < 0.025), but decreased total nitrogen and protein in tubers stored at 5°C. Treating potatoes with CIPC prevented sprouting in both varieties and apparently caused the tuber to retain nitrogen.