Hot Break Research Articles

Quality evaluation of slightly concentrated tomato juice produced under high pressure conditions

Consumer acceptance of tomato products is highly correlated to their organoleptic characteristics and quality parameters such as color and texture. Textural properties of tomato juice can be attributed to the activity of pectinolytic enzymes such as pectinmethylesterase and polygalacturonase. High pressure processing has been proposed as an alternative physical method for intrinsic tomato enzymes inactivation. The objective of this work was to evaluate the quality characteristics of slightly concentrated tomato juice produced under high pressure conditions. Whole tomatoes (var. Red Sea) were pressure-treated at 250, 400, 500 or 600MPa and 50°C for 10min. The processed tomatoes were then crushed, the peels and seeds were removed, and the resulted tomato juice was concentrated to 8.5°Brix. The viscosity, consistency and color of the concentrated juice were measured and compared to the corresponding properties of tomato juice, at the same concentration, produced under the traditional methods of both cold and hot break. High pressure processing did not affect the color of tomato juice at all pressure levels tested, while during hot break color deterioration was always observed. Pressure treatment at 400, 500 and 600MPa led to products of higher viscosity. Increase in applied pressure resulted in an increase in product viscosity and improved consistency. High pressure processing can be used to produce minimally heat processed products with nutritional and sensorial characteristics comparable to that of fresh fruit. It provides a successful alternative to traditional thermal processing leading to products with desirable, or even predesigned, characteristics.

Impact of Harvesting and Processing Conditions on Green Leaf Volatile Development and Phenolics in Concord Grape Juice

The disruption of plant cell walls during fruit juice processing results in the enzymatic formation of herbaceous-smelling green leaf volatiles (GLVs). Our objective was to assess the impact of thermal processing conditions on resulting levels of GLVs (hexanal, trans-2-hexenal, hexanol, cis-3-hexenol, and trans-2-hexenol), total phenols, monomeric anthocyanins, and percent polymeric color in Concord grape juice. The effects of fruit maturity and stage of juice processing on juice GLV content was also assessed. Of the GLVs studied, only trans-2-hexenal routinely exceeded its published sensory threshold in finished juice. We observed an inverse linear correlation between berry maturity (total soluble solids) and trans-2-hexenal levels in finished juice (P < 0.05, R(2)= 0.91). Trans-2-hexenal was at a maximum immediately following crushing (569 microg/kg, >30-fold over detection threshold [DT]), decreased to 100 microg/kg following depectinization, pressing, and pasteurization, and to 32 microg/kg following cold-stabilization. The loss of trans-2-hexenal could be explained primarily by its reduction to trans-2-hexenol, which increased from 53 microg/kg after crushing to 500 microg/kg after cold-stabilization. High temperature pretreatment of must immediately following crushing ("hot break") resulted in 5- to 6-fold higher concentrations of trans-2-hexenal in the final bottled juice as compared to conventional hot press. Contrary to expectations, no significant increase in phenolics and anthocyanins were observed in hot break conditions. These results indicate that hot break procedures may thermally inactivate enzymes responsible for transforming trans-2-hexenal under normal processing conditions and potentially alter the flavor qualities of the finished Concord juice. Different equivalent pasteurization regimes (82 to 93 degrees C) prior to bottling had no significant effect on GLV content of the finished Concord juices (P > 0.05). Introducing new processing techniques to fruit juice production can potentially result in undesirable changes to organoleptic properties. We have observed significantly higher levels of trans-2-hexenal, a potent herbaceous off-flavor, in Concord grape juice prepared with an initial high temperature heat treatment ("hot break"). Concord juice producers should be cautious in using hot break processing, especially with immature fruit, as it may result in persistence of green aromas in juice.

Writings on the Dark Side of Travel

Thursday, 11 August 2005. Killing time, I visit the Museum of Tolerance in Los Angeles. This is coming to the end of a tour of the Arthur Murray dance studios up and down the West Coast. It is a hot break coming at the end of a month’s dance fieldwork in Sacramento. Rather than fly back to Belfast from San Francisco, I opted for LAX and bookended my research with a personal journey driving up and down the state. I had gone up through Death Valley where I had solo hiked into the desert and made a souvenir vial of Death Valley sand. Then inland north to get through Yosemite, living in my rental car, sleeping in motels. Back south, I was sampling the dance studios along the coast—waltz in San Francisco, rumba in Hayward, foxtrot in Redwood City, tango in San Jose, salsa in chic Santa Barbara, merengue in Beverley Hills. Along the way, I was taking in the tourist attractions: the boardwalk in Santa Cruz where the movie Lost Boys was filmed; Cannery Row, Monterey, described long ago by John Steinbeck; Hearst Castle, which had inspired Orson Welles’s Citizen Kane.

Dissipation of Profenofos, Imidacloprid and Penconazole in Tomato Fruits and Products

An experiment was conducted to evaluate the effects of some technological processes on the residual levels of profenofos, imidacloprid and penconazole in tomato fruits and products. According to their half-life (t (1/2)) values, tomato fruits can be safely harvested for human consumption or for processing purposes 3 days after the spray time of imidacloprid and penconazole and 7 days after in the case of profenofos. Pesticide residues were greatly decreased in tomato juice under cold or hot break compared with that taken from unwashed tomato fruits. A sharp decline in profenofos level was noted after treatment by pectinex ultra SP-L and benzyme M during tomato crushing.

Analysis of cell-wall pectin from hot and cold break tomato preparations

Abstract The initial processing of tomatoes includes a break step, which involves rapid heating of the freshly chopped tomatoes to >90 °C for hot break, or 60–77 °C for cold break. It is believed that pectolytic enzyme deactivation is the key element in the hot break step; therefore the pectin content of the different products should be qualitatively distinct. There are two general sources of pectin in a tomato fruit: the middle lamella which is rich in homogalacturonan, and the cell-wall. In this study, a 0-min or 24-min hold time (room temperature) for the chopped tomatoes preceded the break step to replicate hot and cold break, respectively, with minimum variation in the processing. The cell-wall pectin was then isolated and analyzed for the carbohydrate composition, degree of polymerization, and degree of esterification. The results showed no observable differences in pectin isolated from the two preparations, indicating that there is no significant pectolytic activity in the cell wall during the 24 min hold time; thus, the pectolytic enzymes probably act on the lower ester, middle lamella pectin in cold break products.

Changes in bioactive compounds and antioxidant activity during homogenization and thermal processing of tomato puree

The effect of homogenization and thermal processing on a number of bioactive compounds (carotenoids, total phenolics, ascorbic acid and folates) in both raw tomato puree (RTP) and “hot break” tomato puree (HTP) was investigated. RTP and HTP were homogenized in either one or two-steps, followed by pasteurization at 98 °C for 40 s. Additionally, HTP was pasteurized in parallel at 98 °C, 108 °C and 128 °C. In general, homogenization had no effect, but changes were observed after pasteurization (98 °C for 40 s). Carotenoids were relatively resistant to thermal degradation, whereas total phenolic content and ascorbic acid significantly decreased. However, a higher content of folates was determined in the homogenized and pasteurized samples due to their higher extraction from the subcellular compartment. The increase in pasteurization temperatures of the HTP up to 128 °C led to a decrease of ascorbic acid, total phenolic compounds and folates. In conclusion, homogenization and pasteurization at 98 °C for 40 s improves the nutritional value of tomato puree, increasing the extractability of the folates and maintaining the carotenoid content.

Changes in Pectins and Product Consistency during the Concentration of Tomato Juice to Paste

Concentrating tomato juice to paste during the tomato season allows for preservation and long-term storage, but subsequent dilution for formulation of value-added products is known to result in a loss of consistency. To understand the reasons for this, samples of unconcentrated juice, processing intermediates, and concentrated paste were collected from an industrial processing plant during normal commercial production. All samples were diluted with water to 5 degrees Brix and then analyzed for consistency and pectin content. Whole juice consistency, measured with a Bostwick consistometer, decreased through the course of juice concentration, with the largest change occurring early in the process, as the juice was concentrated from 5 to 10 degrees Brix. This decrease in consistency occurred during the production of paste from both hot- and cold-break juices. The change in Bostwick value was correlated with a decrease in the precipitate weight ratio. The loss of consistency during commercial processing was not the direct result of water removal because a sample of this same 5 degrees Brix juice could be concentrated 2-fold in a vacuum oven and then diluted back to 5 degrees Brix with no change in consistency or precipitate ratio. Total pectin content did not change as the juice was concentrated to paste, but the proportion of the total pectin that was water soluble increased. The greatest increases in pectin solubility occurred during the hot break and late in the process where the evaporator temperature was the highest.

VISCOSITY AND QUALITY OF TOMATO JUICE AS AFFECTED BY PROCESSING METHODS

ABSTRACT Quality and viscosity of tomato juice is strongly governed by mechanical and thermal abuse during processing. The effect of processing and storage duration on the viscosity and quality parameters of tomato juice was evaluated in the present work. Tomato juice was obtained by two different methods, normal method (NM) and variable method (VM), and was heated by both conventional and microwave hot break treatments. Tomato juice was evaluated for various quality characteristics including precipitate weight ratio, degree of serum separation (DOSS), Brookfield viscosity, lycopene levels, vitamin C, phenols and antioxidant activity. Changes observed in several quality parameters during storage were statistically insignificant. The methods and processing had the greatest contribution toward viscosity, whereas storage duration had no significant effects. Viscosity parameters viz precipitate weight, DOSS and Bostwick consistency revealed that juice processed by VM was more viscous than that of NM, irrespective of the hot break processing used. Ascorbic acid and lycopene content varied significantly with mechanical methods and processing conditions. However, phenolic content and antioxidant activity remained stable. The variable process represents an improvement over the conventional by enabling tomato processors to improve the consistency of the tomato product.PRACTICAL APPLICATIONSQuartering or slicing tomatoes followed by hot break processing techniques can significantly improve the quality of tomato juice in terms of reduced degree of serum separation and precipitate weight ratio. The modified technology could be considered as a viable and economical method for small‐ and medium‐scale tomato processors with limited resources and facilities at their disposal.

Effect of thermosonication on quality improvement of tomato juice

Inactivation of pectinmethylesterase (PME) and polygalacturonase (PG) is required to minimize quality loss in tomato products. Tomato juice was subjected to thermosonication (TS) (24 kHz), at amplitudes of 25, 50 and 75 μm at 60, 65 and 70 °C or heat only treatments. The TS treatment at 60 °C, 65 °C and 70 °C for 41.8, 11.7 and 4.3 min exposure, respectively reduced PME activity by 90%. The heat only treatment at 60 °C, 65 °C and 70 °C for 90.1, 23.5 and 3.5 min, respectively inactivated PME by 90%. TS treatments with 25–75 μm amplitude had no significant impact on the inactivation efficiency between 60 and 70 °C. After TS the average particle size decreased noticeably (< 30 μm) and viscosity increased 2–4 fold, compared to the heat treated or untreated juice (180 μm). These results suggest that TS at 60 and 65 °C could be useful to obtain tomato juice with a low residual PME activity and high viscosity. Industrial relevance The processed tomato industry is constantly in search for potential alternative processes to conventional “cold break” and “hot break” treatments that could inactivate the pectic enzymes of importance. The findings of this study would help the industry to inactivate pectinmethylesterase (PME) enzyme at a lower temperature range and also achieve a higher viscosity due to the mechanical effects of thermosonication. Low temperature treatment would enable the retention of fresh-like properties of tomato juice. Based on the findings of this study, thermosonication could be considered as a potential alternative to conventional “cold break” and “hot break” treatments of tomato juice.

Rheological and structural characterization of tomato paste and its influence on the quality of ketchup

Three hot break tomato pastes were investigated to determine the effect of their characteristics on the properties of tomato ketchup, processed in an industrial-scale facility (i.e. diluted, heated, homogenized and cooled). Pastes and ketchups were characterized by particle size distribution, volume fraction, and rheological behavior in steady and dynamic shear. The ketchups were also subjected to sensory assessment. The processing of pastes into ketchups induced large structural changes, which were reflected in all parameters studied. The volume fraction of solids ( φ) accurately reflected the changes that the paste suspensions underwent during processing and it appeared to be a good predictor of the flow behavior of both the pastes and the ketchups. The corresponding flow curves were found to be well described by the Carreau model in a large range of shear rates and concentrations. However, the rheological characteristics of the commercial pastes studied did not directly correlate to those of the corresponding ketchups. Instead, our results suggest that the change in structure induced by processing might be governed by other properties of the paste, such as the fraction of small and large particles and their sensitivity to breakage, together with the viscosity of the aqueous phase.

Simulation investigations of the effects of whirlpool dimensional ratios on the state of secondary whirls

The rotating flow field in a cylindrical vessel of a centrifugal-settling vat – the so-called whirlpool – finds the wide application in brewery technology for the separation of solid particles, i.e. hot break. The phenomenon of the conically shaped concentration of sediment reaching the vessel bottom is utilized in this installation. The process of sediment separation in standard whirlpools is carried out with the discharge head H equal to the diameter of a vessel, so the H: D ratio is usually 1. An analysis of the spin-down velocity distribution carried out on the basis of computer simulation results was aimed to establish the effects on liquid clarification and formation of sediment cone.

Preliminary studies on the effect of processing on the IgE reactivity of tomato products

Tomatoes and tomato products, obtained from a market, from companies or prepared in research laboratories, were tested in order to investigate how different processes could modulate the IgE reactivity of these products. The protein fraction of the samples was extracted by using a low-temperature method in order to avoid degradation, and then separated on SDS PAGE to evaluate the protein profile. All the separated samples were blotted onto nitrocellulose membranes and then individually tested with pooled human sera that had been obtained from patients allergic to tomato, in order to evaluate the potential IgE binding of the protein bands. Heat treatments conventionally employed for the production of tomato-based products were found to strongly degrade proteins thus dramatically reducing their IgE reactivity; characteristic protein profiles were found for specific processes such as hot and cold break. Ultra-high-pressure treatments were found to generally preserve the integrity of tomato proteins and this was reflected by the unaltered IgE reactivity observed. Copyright © 2007 Society of Chemical Industry

Effect of Process Conditions on Composition and Properties of Pectin and Apparent Viscosity of Sterilized and Concentrated Pulp of Tomatoes

Tomato pulp treated at industrial unit conditions was utilized to determine the physical and chemical changes on pectin substances properties and its correlation to the consistency of tomato pulp, hot break pretreated product, concentrated pulp at 70oC/30 min and sterilized pulp at 102oC/10 min. The assays carried out were: apparent viscosity, serum separation degree, precipitate weight ratio, insoluble solids and pectic substances as uronic acid, fractionated according to their solubility in water, 0.2% ammonium oxalate, 0.05N hydrochloric acid and 0.05N sodium hydroxide solutions. Concentration and sterilization cause reduction in the apparent viscosity, the precipitate weight ratio and increasing of the serum separation degree of the suspension compare to tomato pulp submitted only to pre-treatment and those conditions didn’t affect significantly the total uronic acid and insoluble solids in water. However, changes occurred on chemical composition, detected into fractions of pectic substances expressed as uronic acid in all samples; results for pre-treated pulp sample to sterilized pulp samples (final product) show a high water solubilization of the fractions of the pectic substances, around 31%, confirmed by an increment of 24% in the water soluble fraction. A high correlation was established between the concentration of water-insoluble fractions and apparent viscosity, precipitate weight ratio and serum separation degree.

Effects of Commercial‐scale Pulsed Electric Field Processing on Flavor and Color of Tomato Juice

ABSTRACTEffects of commercial‐scale pulsed electric field (PEF) processing on the flavor and color of tomato juice during storage at 4 deg;for 112 d were studied. Tomato juice was prepared by hot break at 88°C for 2 min and then thermally processed at 92° for 90 s or PEF processed at 40 kV/cm for 57 μs. The PEF‐processed tomato juice retained more flavor compounds of trans‐2‐hexenal, 2‐isobutylthiazole, cis‐3‐hexanol than thermally processed or unprocessed control tomato juice (P &lt; 0.05). PEF‐processed juice had significantly lower nonenzymatic browning and higher redness than thermally processed or control juice (P &lt; 0.05). Sensory evaluations indicated that the flavor of PEF‐processed juice was preferred to that of thermally processed juice (P &lt; 0.01).

Flavor, Viscosity, and Color Analyses of Hot and Cold Break Tomato Juices

ABSTRACT: Two methods are used commercially to produce tomato juice: hot break and cold break. Tomatoes were chopped and allowed to sit for various time intervals to simulate the cold break process. Zero was hot break, and 2 to 24 min represented cold break. Sensory, volatile, color, and viscosity analyses were conducted to determine which hold time produced the optimum juice. Sensory panelists rated 15 min cold break most fresh and liked over hot break. Lipoxygenase‐initiated volatiles increased from hot to cold break. No overall color difference was found between hold times. Viscosity decreased from hot to cold break. The cold break process can be used to produce a premium flavored tomato juice.

Changes in cell wall pectins accompanying tomato (Lycopersicon esculentum Mill.) paste manufacture.

The texture of processed tomato products is influenced by the size and solubility characteristics of soluble and particle-bound cell wall polysaccharides they contain. The acidic (pectin) polysaccharides are important contributors to texture because of their gel-forming capability and the fact that they can form aggregates. The present work describes the pectins in ripe tomato fruits and then follows changes in several classes of pectins as the fruits are subjected to hot break and the juice is subsequently concentrated to a 30 degrees Brix paste. Continued processing leads to progressive solubilization and depolymerization of polysaccharides so that the ionically and covalently bound materials that are the major pectin classes of ripe fruit are substantially reduced in amount with the concomitant increase in the more soluble water-soluble pectins of the paste product. Juice content of soluble solids ( degrees Brix) rose steadily as water content was reduced during processing. Juice content of polymeric uronic acids (i.e., pectin) also rose with concentration, but to a lesser degree than the increase in soluble solids. This indicates that processing leads to almost complete pectin depolymerization and/or the alteration of uronic acid structures so that this assay could no longer detect them. It was concluded that reductions in heat input during processing would lead to pastes with greater pectin integrity and enhanced textural characteristics.

TOMATO ATTRIBUTES AND THEIR CORRELATION TO PEELABILITY AND PRODUCT YIELD

Although tomato paste research has received significant attention, relatively little effort has been addressed to optimization of value-added whole peel and diced tomato processing. Our laboratory has conducted research evaluating tomato attributes which may be indices of peelability and product yield. Eleven tomato varieties were harvested at USDA stage 4 (pink), USDA stage 6 (red) and red plus either 1, 2 or 3 weeks time. Maturity was established by tagging either flowers or pink fruit. Fruit was evaluated for physical attributes, texture, paste quality, peelability and product yield. Physical attributes measured included color, density, height, weight, width, shoulder height, stem scar diameter, locule number and gel state, seed number and weight, pericarp wall thickness and red layer thickness. Paste quality was determined using a microwave hot break procedure and evaluation of raw and cooked color, Bostwick, pH, °Brix, titratable acidity and serum viscosity. Tomatoes were exposed to steam, vacuum and mechanical peel eliminators and then percent peelability and product yield were calculated. Firmness of raw and peeled diced tomatoes was measured using a Kramer shear cell. Discriminant analysis was used to determine which subsets of physical attributes correlated to desirable levels of peelability and product yield. A model equation was developed using four physical attributes, e.g. width, stem scar diameter, pericarp thickness and red layer thickness. Use of the model allowed for prediction of “paste” vs. “whole peel/dice” group allocation with 90% accuracy in pilot scale studies. The model is currently being tested at the commercial scale with California processors.

Processing effects on lycopene content and antioxidant activity of tomatoes.

Consumption of tomato products has been associated with decreased risk of some cancer types, and the tomato antioxidant, lycopene, is thought to play an important role in the observed health effects. In this study, four carotenoids, trans-lycopene, phytofluene, phytoene, and zeta-carotene, were quantified in tomato products. Samples of raw tomatoes, tomato juice after hot break scalder, and final paste were obtained from two different processing plants over two years. Comparison of carotenoid levels throughout processing indicated that lycopene losses during processing of tomatoes into final paste (25-30 degrees Brix) ranged from 9 to 28%. The initial Brix level of the raw tomatoes appeared to influence the amount of lycopene loss that occurred, possibly due to the differences in processing time required to achieve the final desired Brix level of the paste. In general, no consistent changes in the other carotenoids were observed as a function of processing. The antioxidant activity of fresh tomatoes, tomato paste, and three fractions obtained from these products (i.e., aqueous, methanol, and hexane fractions) was also determined. In both a free radical quenching assay and a singlet oxygen quenching assay, significant antioxidant activity was found in both the hexane fraction (containing lycopene) and the methanol fraction, which contained the phenolic antioxidants caffeic and chlorogenic acid. The results suggest that in addition to lycopene, polyphenols in tomatoes may also be important in conferring protective antioxidative effects.

Relationships between the volatile compounds evaluated by solid phase microextraction and the thermal treatment of tomato juice: optimization of the blanching parameters

Tomato juice contains volatile compounds that are originally detected in fruit, such as terpenes, and others that are originated during processing by lipoxygenase activity, carotenoid co-oxidation and Maillard reaction that can be activated during the thermal treatments. This paper reports the analysis of the volatile compounds of tomato juice sampled by solid phase microextraction (SPME) and the optimization of the blanching parameters in tomato juice, using the volatile compounds as markers. One hundred and ninety volatile compounds, including ketones, aldehydes, alcohols, esters, ethers, hydrocarbons, sulfur, nitrogen and oxygen compounds, phenols, oxygen-containing heterocyclic compounds, free acids and lactones, were identified or tentatively identified by the GC–MS technique. The thermal treatment mainly modifies saturated and unsaturated C 6 alcohols and aldehydes, esters, ketones and carotenoid derivatives. The optimal conditions for the blanching, selected by response surface modelling (RSM), were 67°C for 24 min and 86°C for 3.5 min for the cold break and the hot break treatments, respectively.

Changes in chemical composition of tomatoes during processing

The influences of processing conditions and composition on chemical changes during thermal processing of tomatoes were investigated. During the Cold and Hot Break process pectin is degraded to different extents. Due to the thermal impact at first cyclization of glutamine to pyroglutamic acid takes place. At higher dry weight contents and during drying processes Amadori compounds and browning can be detected. The reaction products formed during thermal processing can be analysed by amino acid analysis and-after proper derivatization-by capillary gas chromatography.