عنوان

Microstructural development of high solid food systems during freeze-drying

شماره

TLets760522

عنوان اصلي

Microstructural development of high solid food systems during freeze-drying

نام عام مواد

[Thesis]

نام نخستين پديدآور

Malik, Nur Hafizah

نام ناشر، پخش کننده و غيره

University of Birmingham

تاریخ نشرو بخش و غیره

2018

جزئيات پايان نامه و نوع درجه آن

Thesis (Ph.D.)

امتياز متن

2018

متن يادداشت

Freeze-drying is an energy demanding operation involving dehydration through sublimation of ice crystals. It has important application in the production of high quality dried food such as instant coffee. Correlating the operating conditions with product attributes is essential to design processes that are energy efficient whilst producing product of desired characteristics. In this study, microstructure development and evaluation for gum arabic and coffee solutions during freeze-drying have been considered. Freeze-drying processes were carried by varying the material's concentration (20-60% w/w) and properties as well as freezing and primary drying conditions. Microstructural evaluation and reconstitution behaviour of freeze-dried solids were assessed using scanning electron microscopy, X-ray computed tomography and high resolution camera. Initially, water crystallization was studied under temperature oscillation, slow, fast and unidirectional freezing where large crystal dendrites developed on fluctuating temperature and different freezing rates produced comparable crystal network. At reduced water content, smaller crystals developed and distinct orientation of crystal growth was visible. Meanwhile, at increasing primary drying temperature and concentration, the freeze- dried systems showed extensive structure expansion. The potential of aeration to assist freeze-drying of high solid solutions is demonstrated by improved structure uniformity and porosity. Reconstitution of the freeze-dried solids was influenced by the microstructure generated and physical mechanisms involved during dissolution. High porosity and presence of large pores enable rapid dissolution of the dried solids. Different dissolution mechanisms between gum arabic and coffee had strong impact on the kinetics of dissolution. The concept of process-microstructure-property relationship is thus very clear in this study.

موضوع مستند نشده

TA Engineering (General). Civil engineering (General) ; TP Chemical technology

مستند نام اشخاص تاييد نشده

Malik, Nur Hafizah

مستند نام تنالگان تاييد نشده

University of Birmingham

نام الکترونيکي

فرمت انتشار

p

نوع ماده

[Thesis]

کد کاربرگه

276903

سطح دسترسي

a

تكميل شده

Y