Hard fats, obtained from liquid oils by different fat modification techniques, are composed of highmelting-point triacylglycerols (TAGs) that can be used as alternatives to improve the functional characteristics of lipid systems. These low-cost industrial products are regarded as raw materials in lipid technology. They can behave as modifiers in crystallization processes, acting as preferential nuclei for ordering crystal lattices and inducing specific polymorphic patterns because of their homogeneous TAGs. Adding hard fats, such as mango, illipe, kokum, sal, shea, rambutan, palm oil, palm kernel oil, and sunflower oil, into other oils is beneficial as it increases their compatibility for uses in fat-based products, especially confectionery products. The addition of hard fats has a significant effect on the rate of crystallization, significantly decreasing the induction time for nucleation and leading to a higher hardness, and increases the thermal resistance for applications in fat-based products. The aim of this article is to review the changes in the physicochemical and thermal properties of hard fats and their mixtures obtained by fractionation, enzymatic interesterification and blending, which broaden their applicability in the food industry.

Background: Rambutan (Nephelium lappaceum L.) is an important commercial fruit in southeast Asia and is gaining more attention in recent years because it is juicy and sweet and has a refreshing flavour and an exotic appearance. It is commercialized for fresh consumption and is industrially processed as canned fruit, juices, jams, jellies, marmalades, and spreads. The seed is a major co-product of this industry and is worthy of attention for industrial applications and their feasibility. Scope and approach: This review describes the composition of the rambutan seed, which is examined from a critical interpretation regarding the suitable use of this co-product. This review also compares the total yield, physicochemical and thermal properties of its fat for the purpose of evaluating the potential of this fruit co-product as a source of natural edible fat with potential industrial uses. Key findings and conclusions: Rambutan seed is a major co-product of the industry that has high premium-grade fat, protein, carbohydrate, fibre, antioxidants, and phenolic content and that can be used in several segments of the food, pharmaceutical, and cosmetic industries. Rambutan seed powders are also used as local medicine (they contain antidiabetic compounds) in Malaysia. To determine the effectiveness of raw rambutan seeds in treating diseases, in vivo and human clinical studies should be performed.Research should also continue to determine if rambutan seed fat can be fractionated, chemical and enzymatic interesterified, and blended with other fats to make cocoa butter alternatives. Comprehensive studies are needed on rambutan seed to explore more potential industrial applications. ©

The pre‐treatment of oilseeds prior to extraction process may affect oil yield and quality. The aim of this study was to investigate the effects of two drying methods on rambutan seed fat (RSF) yield and their oxidative stability, physicochemical properties, and crystal morphology. Response surface methodology (RSM) was used in the optimisation and investigation of the effects of three process conditions: seed weight (g), extraction time (min), and solvent volume (ml) on RSF yield. Under optimal conditions, a maximum RSF yield of 44.14% was obtained. The differences between RSF pre‐treated with oven‐drying and RSF with freeze‐drying methods in slip melting point (38.3°C to 39.7°C), free fatty acid (3.13 to 3.50 mg KOH/g fat), peroxide value (1.04 to 1.67 meq of O2/kg of fat), p‐anisidine value (1.10 to 1.56), and total oxidation value (4.21 to 5.67) were significant (p < 0.05). Both fats showed needle‐like shaped crystals. Our results provide useful information in the pre‐treatment of RSF, which has potential to be used as blending component with palm oil for cocoa butter equivalent formulation in chocolate and confectionery industries.

The search for hard fats is increasing by the day due to their demand for industrial purposes. Rambutan seed fat (RSF) was fractionated prior to investigate the melting and crystallisation behaviours, triacylglycerols (TAGs), and morphology using different chromatographic and thermal techniques. The increasing trends were observed for high-melting symmetrical monounsaturated TAGs such as 1,3-distearoyl-2-oleoyl-glycerol and 1-palmitoyl-3-stearoyl-2-oleoyl-glycerol in both solid fractions upon fractionation. The solid fractions (F1-S) and (F2-S) exhibited small peaks towards low melting area and big peaks towards high melting area with the offset temperatures of 35.29-48.75°C and 43.58-52.70°C with significantly higher enthalpies (93.49 and 105.13 J g−1) upon fractionation. F2-S showed the densely packed microstructure compared to that of crude RSF and F1-S. Based on the thermal behaviours as well as morphology of RSF fractions, cocoa butter improver could be prepared that has the potential to be utilised in chocolate manufacturing in tropical countries.

The utilization of rambutan seed (Nephelium Lappaceum L.) to produce fat (RSF) and its fractionation could be one of the solutions for better waste management and for ensuring its sustainable utilization. In this study, RSF was fractionated by two-stage acetone fractionation and their physicochemical properties such as fatty acid compositions, iodine value (IV), free fatty acid (FFA), slip melting point (SMP), and solid fat content (SFC) were investigated. The solid fraction-III (F 2 -S) exhibited the highest SMP (49.03°C) and lowest IV (27.57 g I 2 /100 g). The major fatty acids in all solid fractions were stearic (15.1-21.6%), oleic (25.0-35.5%), and arachidic (42.7-46.9%) acids. The SFC of F 2 -S at 20°C (78.57%) and 35°C (22.95%) were found to be higher than solid fraction-I (F 1 -S), indicating a harder solid fraction. This study revealed that by performing fractionation of RSF, a cocoa butter improvers (CBI) could be prepared by blending them with other fats that have the potential to be utilized in chocolate manufacturing in tropical countries.