Palm Mid Fraction Research Articles

Solid fat content and bakery characteristics of interesterified beef tallow-palm mid fraction based margarines.

Palm mid fraction (PMF) was interesterified with edible beef tallow (BT) catalyzed using sodium methoxide to investigate the effects on the solid fat content (SFC) of these palmitic rich plastic fats. Interesterified blends crystallize more slowly than BT. Conversely, the crystallization rates of PMF-BT-based interesterification (IE) products were compared with the starting mixture and IE products prepared with non-PMF triglycerides. The SFC PMF-based IE products increased significantly at temperatures between 25 and 40 °C. The SFC profiles became smoother and the products had potential to serve as base oils for preparing specialty fats with a wider range of plasticity. Further exploration of triacylglycerol (TAG) compositional changes revealed that PMF interesterified products had greater saturated/saturated/saturated (S/S/S)-type TAGs compared with soybean oil interesterified products. Moreover, in subsequent evaluations of BT-PMF-based IE fats as a margarine replacement effects in a baked cake model system showed that the material was a suitable functional oil base with acceptable aeration properties and plasticity during baking. Therefore, it is a potential alternative to IE-BT based and traditional IE-BT-palm oil based margarines. The physical-characteristics of bakery products prepared with this fat exhibited improved cake volume with fine structure and clear lifting properties, which affirmed the potential for its application in bakery fats.

Characteristics of palm mid-fractions produced from different fractionation paths and their potential usages

ABSTRACTThree palm mid-fraction (PMF) groups produced from different fractionation paths were analyzed in terms of the fat, triacylglycerol and sn-2 fatty acid compositions, thermal properties (melting and crystallization behaviors, and solid fat contents (SFCs)), micronutrient levels and oxidative stability indexes (OSIs) to achieve their sufficient utilization. PMF-A (iodine value (IV), 48.4 g/100 g) fractionated from palm olein contained 43.8% 1,3-dipalmitoyl-2-oleoyl-glycerol (POP) and 16.7% 1-palmitoyl-2,3-dioleoyl-glycerol, showing soften properties (slip melting point (SMP), 27.6°C; SFC at 30°C, 2.2%) at hot weather. PMF-B (IV, 42.3 g/100g) obtained from palm stearin showed similar fat and triacylglycerol compositions as PMF-A, but the high 1,2,3-tripalmitoyl-glycerol level (6.2%) improves its thermal behaviors (SMP, 34.9°C; SFC at 30°C, 13.8%). The SFC profiles of PMF-A and PMF-B were comparable to those found in frozen and puff margarine shortenings. Furthermore, both of the PMF groups exhibited excellent OSIs (13.2 and 11.2 h, respectively) because of their high micronutrient levels (especially γ-tocopherol and campesterol). In general, γ-tocopherol and campesterol contribute to preventing lipids from oxidation under frying conditions. Therefore, PMF-A and PMF-B are recommended for manufacturing margarine shortenings and frying fasts. PMF-C (IV, 33.0 g/100g) produced from the additional fractionation of PMF-A or PMF-B contained the highest POP percentage (67.1%) and showed heat-resistant property (SMP, 31.8°C; SFC at 30°C, 22.4%). Its steep SFC profile was superior to that of cocoa butter, suggesting the fat is preferred in producing hard chocolate fats.

Epitaxial Growth of Fat Crystals on Emulsifier Crystals with Different Fatty Acid Moieties

We performed in situ observations of the crystallization and melting behaviors of palm mid fraction (PMF) on sorbitan ester (SE) crystals comprising different fatty acid moieties (sorbitan tripalmitate (STP), sorbitan tristearate (STS), or sorbitan tribehenate (STB)) to reveal the epitaxial relationship between fat crystals and emulsifier crystals. The effects of SEs on the thermal behavior and polymorphism of PMF were investigated by differential scanning calorimetry and synchrotron radiation X-ray diffraction. These measurements showed that the addition of STP and STS greatly increased the crystallization temperature of PMF, which was caused by the crystallized SEs that were nucleated prior to PMF. Microscopic observations demonstrated that PMF crystals were oriented in the same direction as crystals of STP and STS because the chain lengths of the fatty acid moieties were similar to those of PMF. In contrast, when STB was used as a substrate, PMF crystals were not oriented in the same direction as STB crystals because there is a large difference between the chain lengths of STB and PMF. These results revealed that crystal growth of PMF on STP and STS crystals occurs via epitaxial growth, whereas PMF crystallization on STB crystals occurs via general heterogeneous nucleation.

Templating effects of dipalmitin on soft palm mid-fraction crystals

ABSTRACTThe crystallization of lipids has important implications for the industrial processing of food products, such as chocolates, margarines, spreads, confectionery, as well as bakery and dairy products. Thus, blends of soft palm mid-fraction (PMF) and dipalmitin (PP) containing PP of 0.5 g/100 g and 1.0 g/100 g were investigated under stabilization time and conditions for controlling and improving the crystallization step of fat during fat modulation. Crystallization results showed by reducing the Avrami parameters tsfc, t1/2, and k, the addition of PP accelerated the crystallization process of PMF. Changes in the crystals morphology observed by polarized light microscopy gave a higher crystallized area and reduced crystals size in the microstructure of the PMF, which was also verified by the increase in melting point and solid fat content (SFC). The addition of PP caused changes in the arrangement of the PMF triacylglycerols (TAGs), by stabilizing the β´stable polymorphic form, thereafter stabilizing the melting profile and the consistency of PMF over time. These results have interesting implications in the fat and oil industry as they allow for the marketing of products with improved crystallization properties and the stabilization of more stable polymorphic forms, expanding the range of applications of slow-crystallizing fats.

パーム油中融点分別脂(PMF)o/wエマルションの結晶化におけるポリグリセリン脂肪酸エステルの添加効果(結晶多形シンポジウムIII)

パーム油中融点分別脂(PMF)o/wエマルションの結晶化におけるポリグリセリン脂肪酸エステルの添加効果(結晶多形シンポジウムIII)

Cocoa Butter Substitute (CBS) Produced from Palm Mid‐fraction/Palm Kernel Oil/Palm Stearin for Confectionery Fillings

AbstractThis study investigated the physicochemical properties of ternary mixtures of palm mid‐fraction (PMF):refined bleached deodorized palm kernel oil (RBDPKO):refined bleached deodorized palm stearin (RBDPS) for cocoa butter substitute (CBS). Fatty acid constituents, triacylglycerol constituents, solid fat contents (SFCs), melting behavior, polymorphism and crystal morphology were determined using gas chromatography (GC), high‐performance liquid chromatography (HPLC), differential scanning calorimetry (DSC), pulsed nuclear magnetic resonance (p‐NMR), X‐ray diffraction (XRD) and polarized light microscopy (PLM), respectively. Eight blends of various ratios of ternary mixtures were investigated based on the previously studied binary fat mixtures. The composition of palmitic (P) and oleic (O), POP, and crystal morphology (size and shape) of the PMF/RBDPKO/RBDPS [14.9/59.6/25.5 (%w/w)] mixture were comparable to cocoa butter (CB), while its melting profile (18.5 and 37 °C), SFC at 20 °C and polymorphism were different from CB. The iso‐solid diagrams of the mixture displayed a monotectic effect at 20–25 °C. Therefore, the 14.9/59.6/25.5 PMF/RBDPKO/RBDPS mixture could be used as a CBS in confectionery fillings because of the crystal morphology and monotectic behaviors comparable to those of CB.

Blending of Palm Mid‐Fraction, Refined Bleached Deodorized Palm Kernel Oil or Palm Stearin for Cocoa Butter Alternative

AbstractThis study evaluated the physicochemical properties of palm mid‐fraction (PMF), refined bleached deodorized palm kernel oil (RBDPKO) and refined bleached deodorized palm stearin (RBDPS) as binary mixtures in terms of their fatty acid compositions (GC), triacylglycerols (HPLC), solid fat contents (p‐NMR), melting behaviors (DSC) and polymorphisms (XRD) for cocoa butter (CB) alternative formulations. All the PMF/RBDPKO and RBDPS/RBDPKO blends showed mixtures of short/long‐chain fatty acids with corresponding triacylglycerols. 10–70 % PMF in RBDPKO showed a eutectic effect between 20 and 30 °C. However, a monotectic effect was observed at 10–15 °C for 20–40 % PMF in RBDPKO and 40–80 % of RBDPS in RBDPKO. For PMF/RBDPS blends, a monotectic effect was observed at less than 30 °C. Broad endotherms at 20–38 °C were observed for 30–50 % RBDPS in RBDPKO which are closer to CB, with polymorphs of β′1 > β′2 ≫ β2 based on XRD analysis. 50–80 % PMF in RBDPS exhibited significantly higher contents of long‐chain fatty acids with the exception of stearic and lower constituents of monounsaturated triacylglycerols compared to CB. Broad endotherms were observed at 20–38 °C for 50–80 % PMF in RBDPS which are closer to CB, with β′1 ≫ β′2 > β2. Therefore, 20–40 % PMF in RBDPKO, 30–50 % RBDPS in RBDPKO and 50–80 % PMF in RBDPS could be used as CB substitutes because of their comparable physicochemical behaviors.

Functionality of cocoa butter equivalents in chocolate products

Although cocoa butter (CB) is an ideal fat for the use in chocolate, limited supply, high demand and fluctuating prices lead the industry to look for alternatives. In the present study, physicochemical properties of commercially available cocoa butter equivalents (CBE) and hard palm mid fraction (PMF) are compared with those of CB. Subsequently, their functionality in real and compound chocolate was evaluated. CBE and PMF contained a comparable (12.0–13.8 %) but significant lower amount of POSt compared to CB (38.7 %). Differences in nonisothermal crystallization and melting profile were observed between CB and CBE. The two-step isothermal crystallization at 20 °C showed that the nucleation started earlier as the StOSt content increased. No significant differences were observed in melting behavior between the reference chocolate (ChocREF) and the chocolates with partial replacement. Hardness was significantly higher for ChocREF. Differences in flow behavior were demonstrated in yield stress, but plastic viscosity of all chocolate products was similar. Although instrumental analyses defined differences, the trained panel and consumers had difficulties to distinguish the chocolate products produced from CBE.

Prevention of oil migration in palm mid fraction and palm olein using a stabilizer rich in behenic acid

Oil loss is a common problem in high oil volume fraction fat-structured foods, where trans fatty acids are absent and saturated fatty acids minimized. Usually a stabilizer “fat”, rich in behenic and stearic acids is added to these products. This stabilizer significantly reduces oil migration and loss; however, the mechanism by which it exerts its effect is not known. Here we study the structure and oil loss characteristics of blends of palm mid fraction (PMF) and palm olein (PO) mixed with a commercial stabilizer of fully hydrogenated cottonseed and rapeseed oils added at 1.25, 3.5, and 7% (w/w) levels. The addition of as little as 1.25% stabilizer reduced oil migration from 13% to ~2% for the 80:20 PMF/PO blend and from 29% to ~3.5% for 20:80 PMF/PO blend after 14days of storage at 20°C, as judged from a filter paper assay. Polarized light microscopy results demonstrated that addition of stabilizer decreased fat crystal size and lead to the formation of a denser network with smaller pores. The rate of crystallization, determined by monitoring increases in solid fat content as function of time by pulsed NMR, increased upon addition of the stabilizer as indicated by decreases in the half-time of crystallization. Addition of stabilizer lead to an increase in the mechanical strength of the material, as indicated by increases in breaking force. Differential scanning calorimetry showed the formation of a new fraction, intermediate between the high melting fractions in both PMF and PO and the stabilizer upon incorporation of the stabilizer in the blends. We hypothesize that the stabilizer helps the formation of this new fraction which has a higher nucleation rate and thus forms a denser network of small crystals with an improved ability to bind and retain oil.

A comparative study on microstructure, texture, rheology, and crystallization kinetics of palm‐based diacylglycerol oils and corresponding palm‐based oils

Palm based diacylglycerol (P‐DAG) oils not only have health‐enhancing properties but also have distinct physicochemical characteristics. However, comprehensive information on the microstructure, rheology, and crystallization properties of P‐DAG oils have yet to be conducted. Thus, P‐DAG oils produced from palm stearin (PS), palm mid fraction (PMF), palm oil (PO), and palm olein (POL) were compared with corresponding palm based oils (P‐oils) in terms of SFC, crystallization properties, rheology, hardness, and microstructure. On the basis of Avrami constant (k) and exponent (n), P‐DAG oils showed higher nucleation and crystallization rate than P‐oils and displayed no spherulitic crystal growth at all examined supercoolings. The complex modulus and phase angle indicated P‐DAG oils except palm stearin DAG (PS‐DAG) appeared to show more strengthening network structure and more solid‐like nature compared to corresponding P‐oils. Substantial changes in crystals size and shape were detected in morphological images of P‐DAG oils excluding PS‐DAG compared to corresponding P‐oils. Nevertheless, all P‐DAG oils showed extremely similar microstructural images with compact structures of very small needle‐like crystals.Practical applications: This study provides valuable information about the microstructure, texture, rheology as well as the crystallization kinetics of palm‐based diacylglycerol oils. These informative data will contribute to exploitation and application of P‐DAG oils in plastic fat products in the future, which exhibited not only nutritional properties to treat obesity but also distinct physicochemical characteristics.Palm based diacylglycerol (P‐DAG) oils were produced from palm stearin, palm mid fraction, palm oil, and palm olein. A comprehensive information on solid fat content, crystallization properties, rheology, hardness, and microstructure of P‐DAG oils were conducted in comparison with corresponding palm based oils (P‐oils). Summarily, substantial differences in these properties of P‐DAG oils were detected compared to corresponding P‐oils.

Sucrose behenate as a crystallization enhancer for soft fats

The addition of sucrose behenate for the modification of the physical properties of soft fats, such as soybean oil-based interesterified fat, refined palm oil, and palm mid fraction was studied. The addition of sucrose behenate was verified to affect the crystalline network of fats, changing the hardness and solids profile. The isothermal crystallization behaviors of the fat blends with 1% sucrose behenate were analyzed at 20 and 25°C. Temperature had a greater effect on the speed of crystallization (k) than the presence of the emulsifier. Sucrose behenate did, however, influence the crystallization mechanism, with changes observed in the Avrami exponent (n). These changes were also observed in the microstructure of the fats. Changes in the polymorphic behavior were observed with the addition of sucrose behenate, such as a possible delay in the α→β transition for interesterified fat, and the initial formation of the β polymorph in palm oil.

Influence of Enzymatic Remediation on Compositional and Thermal Properties of Palm Oil and Palm Oleins from Dry Fractionation

AbstractCharacteristics of crude palm oil are high FFA and DAG contents. High DAG content may affect throughput and yield during fractionation: high‐grade specialty fats such as hard palm mid fraction require premium crude palm oil to secure adequate crystallization properties. Moreover, DAGs are generally considered the main precursors for the formation of glycidyl esters during high‐temperature deodorization. The purpose of this study was to investigate the effect of enzymatic remediation on the reduction of FFA and DAG in crude palm oil. In practice, series of process parameters (vacuum and reaction time) were investigated, and the quality of enzymatically remediated crude palm oils was examined in terms of FFA and DAG reduction, TAG composition, and SFC and DSC melting profiles. Fully refined enzymatically remediated palm oils were then dry fractionated. The quality of the oleins derived from the enzymatically remediated palm oil was compared to that of regular RBD palm oleins.

Effect of animal fats on the physical properties of palm fat

Palm fat is one of the most commonly used fats in food industry. The main role of palm fat is to develop the desired texture of food products. Fat blends were developed to find the most appropriate mixture fitting the technological needs. In our work palm mid fraction (PMF) was mixed with anhydrous milk fat (AMF), goose fat (G), and lard (L) in a 1:1 ratio. Anhydrous milk fat represents fat consisting of a wide range of fatty acids. Goose fat is a soft, easily melting fat, and lard is characterized as animal fat with wide melting temperature interval. The measurements aimed to establish the miscibility of the fats and the effect of animal fats on the melting-solidification profile of palm mid fraction. SFC vs temperature curves, Differential Scanning Calorimetry (DSC) melting thermograms describe the melting profile of the samples. Isotherm crystallization by SFC vs time curves and DSC cooling thermograms were measured to characterize the solidification of pure fats and the blends. Since the SFC curves di...

Monitoring batch lipase catalyzed interesterification of palm oil and fractions by differential scanning calorimetry

The melting profiles of palm oil, palm olein, and soft palm mid fraction were investigated by differential scanning calorimetry (DSC) before, during and after enzymatic interesterification. The DSC melting profiles of the three palm fats changed drastically due to the random redistribution of the fatty acids on the glycerol occurring upon interesterification. A high melting peak (already present for native palm oil) was observed for the three interesterified products and attributed to the increase in trisaturated triacylglycerols; modifications of the shape of the medium-melting peak (observed in the three products) were attributed to modifications within the mono-unsaturated triacylglycerols. In view of the drastic changes observed, the applicability of DSC to monitor enzymatic interesterification reactions was considered. While the degree of interesterification was supposed to be completed after 8 h according to the HPLC data, significant modifications were still observed within the DSC melting profiles. Minor changes within the structure of the medium-melting peak were selected as indicator of the reaction progress, and it was shown that intensities of DSC melting endotherms can be used to monitor the enzymatic interesterification reaction of these palm products.

Physicochemical Properties of Blends of Palm Mid‐Fraction, Palm Stearin and Olive Oil

AbstractWith increasing consumer awareness of risks associated with a high‐fat‐intake diet, the market for reduced calorie fats has been expanding. Ten different ratios of ternary blends of palm mid‐fraction (PMF), palm stearin (POs) and olive oil (OO) were formulated. The solid fat content of all blends at 37C was in the range of 0.00–24.88%, slip melting points ranged from 0.3 to 53.4C, free fatty acid ranged from 0.14 to 0.34% and iodine value ranged from 35.15 to 87.69%. Fatty acid composition analysis demonstrated that all blends were high in palmitic (12.35–59.95%) and oleic (27.27–71.62%) acids. Higher melting enthalpy was shown by blends with higher degree of saturation. Ternary blends of OO with PMF and POs may be suitable for producing shortening and cocoa butter substitutes with better characteristics than individual oils and fats.Practical ApplicationsTo fulfill the increasing demand for low‐calorie and healthy foods, many studies have been done with a new oil or fat blend with better nutritional value and reduced calories. Oil blending is a common technique practiced and it is cheaper and involves minimum production of by‐products, which are potentially hazardous to health. Blending of palm mid‐fraction (PMF), palm stearin (POs) and olive oil was shown to produce an alternative oil source with better physicochemical properties and nutritional value. The ternary oil/fat blend was found to exhibit better oxidative stability and may be suitable as a cocoa butter substitute.

효소적 Acyl migration을 이용한 비대칭형 재구성지질(1,2-disaturated-3-unsaturated glycerol)의 합성 및 분석

The enzymatic interesterification was performed to produce structured lipids (SLs) with palm mid fraction (PMF) and stearic ethyl ester (STEE) for 1, 3, 6, 9, 12 and 15 hr at 80℃. The reaction was catalyzed by Lipozyme TLIM (immobilized lipase from Thermomyces lanuginosus, amount of 20% by weight of total substrates) in a shaking water bath set at 180 rpm. The optimum condition for synthesis of asymmetric SLs were: substrate molar ratio 1:0.5 (PMF:STEE, by weight), reaction time 6 hr, enzyme 20% (wt%, water activity=0.085) of total substrate and reaction temperature 80℃. After reaction at optimized condition, triacylglycerols (symmetrical and asymmetrical TAGs) from reactants were isolated. POP/PPO (1,3-palmitoyl-2-oleoyl glycerol or 1,2-palmitoyl-3-oleoyl glycerol), POS/PSO (palmitoyl-oleoyl-stearoyl glycerol or palmitoyl-stearoyl-oleoyl glycerol), SOS/SSO (1,3-stearoyl-2-oleoyl glycerol or 1,2-stearoyl-3-oleoyl glycerol) were obtained by solvent fractionation. Finally, refined SLs contained stearic acid of 16.91%. Solid fat index and thermogram of the refined SLs were obtained using differential scanning calorimetry. The degree of asymmetric triacylglycerol in the refined SLs was analyzed by Ag-HPLC equipped with evaporated light scattering detector (ELSD). The refined SLs consisted of symmetric TAG of 41.15 area% and asymmetric TAG of 58.85 area%.

Stearic acids atsn-1, 3 positions of TAG are more efficient at limiting fat deposition than palmitic and oleic acids in C57BL/6 mice

In the present study, we investigated the effect of long-acyl chain SFA, namely palmitic acid (16:0) and stearic acid (18:0), at sn-1, 3 positions of TAG on obesity. Throughout the 15 weeks of the experimental period, C57BL/6 mice were fed diets fortified with cocoa butter, sal stearin (SAL), palm mid fraction (PMF) and high-oleic sunflower oil (HOS). The sn-1, 3 positions were varied by 16:0, 18:0 and 18:1, whilst the sn-2 position was preserved with 18:1. The HOS-enriched diet was found to lead to the highest fat deposition. This was in accordance with our previous postulation. Upon normalisation of total fat deposited with food intake to obtain the fat:feed ratio, interestingly, mice fed the SAL-enriched diet exhibited significantly lower visceral fat/feed and total fat/feed compared with those fed the PMF-enriched diet, despite their similarity in SFA-unsaturated fatty acid-SFA profile. That long-chain SFA at sn-1, 3 positions concomitantly with an unsaturated FA at the sn-2 position exert an obesity-reducing effect was further validated. The present study is the first of its kind to demonstrate that SFA of different chain lengths at sn-1, 3 positions exert profound effects on fat accretion.

Lipase-Catalyzed Acidolysis of Palm Mid Fraction Oil with Palmitic and Stearic Fatty Acid Mixture for Production of Cocoa Butter Equivalent

Cocoa butter equivalent (CBE) was prepared by enzymatic acidolysis reaction of substrate consisting of refined palm mid fraction oil and palmitic-stearic fatty acid mixture. The reactions were performed in a batch reactor at a temperature of 60 °C in an orbital shaker operated at 160 RPM. Different mass ratios of substrates were explored, and the composition of the five major triacylglycerols (TAGs) of the structured lipids was identified and quantified using cocoa butter certified reference material IRMM-801. The reaction resulted in production of cocoa butter equivalent with the TAGs' composition (1,3-dipalmitoyl-2-oleoyl-glycerol 30.7%, 1-palmitoyl-2-oleoyl-3-stearoyl-rac-glycerol 40.1%, 1-palmitoy-2,3- dioleoyl glycerol 9.0%, 1,3-distearoyl-2-oleoyl-glycerol 14.5 %, and 1-stearoyl-2,3-dioleoyl glycerol 5.7%) and with onset melting temperature of 31.6 °C and peak temperature of 40.4 °C which are close to those of cocoa butter. The proposed kinetics model for the acidolysis reaction presented the experimental data very well. The results of this research showed that palm mid fraction oil TAGs could be restructured to produce value added product such as CBE.

Physicochemical properties and crystallisation behaviour of bakery shortening produced from stearin fraction of palm-based diacyglycerol blended with various vegetable oils

The stearin fraction of palm-based diacylglycerol (PDAGS) was produced from dry fractionation of palm-based diacylglycerol (PDAG). Bakery shortening blends were produced by mixing PDAGS with either palm mid fraction, PMF (PDAGS/PMF), palm olein, POL(PDAGS/POL) or sunflower oil, SFO (PDAGS/SFO) at PDAGS molar fraction of XPDAGS=0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%. The physicochemical results obtained indicated that C16:0 and C18:1 were the dominant fatty acids for PDAGS/PMF and PDAGS/POL, while C18:1 and C18:2 were dominant in the PDAGS/SFO mixtures. SMP and SFC of the PDAGS were reduced with the addition of PMF, POL and SFO. Binary mixtures of PDAGS/PMF had better structural compatibility and full miscibility with each other. PDAGS/PMF and PDAGS/SFO crystallised in β′+β polymorphs in the presence of 0.4–0.5% PDAGS while PDAGS/POL resulted in β polymorphs crystal. The results gave indication that PDAGS: PMF at 50%:50% and 60%:40% (w/w) were the most suitable fat blend to be used as bakery shortening.

Hydrogenation of Malaysian Palm Mid Fraction on Pricat Nickel Catalyst Using Pilot and Industrial Units

Palm mid fraction produced from Malaysian palm olein was hydrogenated using industrial catalyst (PRICAT 9910) on both pilot and industrial units. Effects of hydrogenation parameters, including temperature, catalyst concentration, reaction time, and circulation rate on final fatty acid composition and trans-fatty acid content were investigated. Mass transfer limitations were indicated particularly in the industrial plant runs. Mass transfer coefficient in the gas–liquid transfer was identified for various circulation rates. The combined mass transfer resistance at the liquid–solid interface and within the catalyst pellet was calculated as a function of different temperatures and circulation rates.