Solar–geothermal drying/instant controlled pressure drop‐swell drying of mechanically dewatered tomato paste. (14th July 2021)

• Record Type: Journal Article
• Authors: Hadibi, Tarik; Boubekri, Abdelghani; Mennouche, Djamel; Benhamza, Abderrahmane; Besombes, Colette; Allaf, Karim
• Is Part Of: Journal of food process engineering. Volume 44:Number 10(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-07-14
• Subjects: Food industry and trade -- Periodicals; Food -- Analysis -- Periodicals; 664.005
• DOI: 10.1111/jfpe.13811
• Languages: English
• ISSNs: 0145-8876

Abstract

Abstract: The economic value of many fruits and vegetables is closely related to their suitability for processing and preservation. In the case of tomatoes (about 94% wet basis wb), the manufacture of 1 kg of dry basis (db) powder (5% wb) or concentrate (30% wb) requires the evaporation of 15.9 or 15.7 kg H2 O/kg db, respectively. In the current study, mechanical dewatering and geothermal‐assisted solar drying (SD) of tomato paste at 5.8 kg H2 O/kg db allowed reaching the required final moisture level of 0.053 ± 0.002 kg H2 O/kg wb with low‐cost energy. The instant controlled pressure drop (DIC) was used for texturing the predried tomato paste using the operative parameters of absolute saturated steam‐pressure P = 0.3 MPa and thermal holding‐time t = 30 s. The final hot air‐drying step of tomato paste was carried out at 39, 50, and 70°C with a constant velocity of 3 m s −1 . The phenomenological modeling of the drying kinetics allowed identifying the starting accessibility and the effective water diffusivity. DIC texturing reduced drying time from 7 to 1.5 hr and improved the effective water diffusivity from 1.43 × 10 −9 to 3.67 × 10 −9 m 2 s −1 for T = 70°C. The lowest activation energy was recorded for DIC samples with 25.69 kJ mol −1 compared with 41.87 kJ mol −1 for control samples. A comparison of visual quality revealed a huge enhancement for DIC‐samples compared with the control samples (RM). Moreover, the high economic value of dewatered tomato water was noticeable. Practical Applications: High quality, low energy consumption, and processing time are decisive factors for the industrial drying operations of agro‐products. Solar–geothermal drying combined with innovative treatment technology called instant controlled pressure drop (DIC)‐swell drying can be a good alternative to conventional drying methods such as hot air drying. Mechanical dewatering as a first step followed by solar–geothermal drying/DIC‐swell drying may greatly reduce drying time and improve the quality of the dried product on the one hand, and reduce energy consumption on the other hand. In addition to that, mechanical dewatering and separation allow us to benefit the peels and seeds, in addition to free product juice with less energy.