Over the past view weeks I have come across several rather focussed processing reports which I thought it was worhgwhile to share here in a simple form. I believe the image tells you what its about and clicking will open the document. The documents I link will generally be technology heavy although there will be there industry issues covered in detail.
I have always been a promoter of sun and solar drying, because they allow people to convert perishable fruit, often available at low or no cost during the season, into a stable product that can be stored until the next season at almost no or low cost.
This article provides some good information on the drying process, that helps in deciding how to actually dry.
The article is an in depth one and gives some really interesting data on drying rates. It compares theoretical with measured rates and is then able to model the progress of drying with this data. The graph below is a really clear indication of the main difficulty of solar powered systems – they only work for a part of the day.
This is particularly important in drying, were it means that sun drying carries on for 3 days. This is because, as the graph shows, drying actually only carries on for a fraction of the day. This fraction depends on the location. This is obvious, but for me only really became clear when I saw this graph!
This has implications for how you run your drying. First of all, it's no good having a nice social day picking, transporting, washing, selecting and preparing your fruit and getting it out into the sun in the late morning or even worse the afternoon. If you do you are going to need four days to dry. More importantly the fruit will be wetter at the end of drying on the first day and therefore more likely to spoil overnight. So rise early and get the fruit ready for the moment when drying can start. Secondly, because the whole drying period until your fruit is shelf stable is many times longer, the cleanliness and hygiene of the plant become more important to avoid spoilage and loss.
Here is a nice story that shows how easy it is to establish an operating fruit and vegetable drying business.
click the image to visit the website
Menar Meebed of Egypt, has used a commercially available solar dryer and a simple Internet blog to set up a business selling dried fruit and vegetables. Her product is of a higher quality than the traditional products because of the fruit she selects and the fact that the solar dryer reduces the drying time.
The commercial success of the business of course depends on how well she sources her produce, whether the market demand for her product is big enough and how she manages the business but the basis is in place.
It is from a project run by University of California, Davis in Tanzania and Nicaragua on the introduction of a Concentrated Solar Power Dryer for the drying of vegetables.
The book carefully explains the steps, starting from a potentially soiled fruit, through preparation, pretreatment, drying and packaging for Tomatoes, Mangoes, Banana, Pineapple, Sapote and Pity (Dragon Fruit).
Simple and clear – its easy to recommend this book.
This short manual from the Technologies and Practices for Small Agricultural Producers (TEAC) website of the FAO describes a simple process for the production of intermediate moisture dried peaches.
click the image to download the manual
The manual is only a few pages long but the process is well explained with a set of photographs of small scale production. There are many other recipes available which I will probably be posting in the future.
This is probably the best technical information I have seen aimed at the training of small scale vegetable and fruit processors. The first book covers the principles of post-harvest handling, storage and processing of fruits and vegetables while the second provides recipes and guidance to put these principles into practice.
click image for free acces to these books
The books We’re developed for trainers working with household processors in Afghanistan, but the information is so comprehensive that it will be useful for a range of users including the new small scale food processing enterprise.
The first book of 85 pages covers the following in detail, using a clear and simple style supported by many photographs and drawings.
WHY DO WE NEED TO PROCESS FRUIT AND VEGETABLES?
POST-HARVEST HANDLING AND STORAGE
PROCESSING: INTRODUCTION TO GENERAL PRINCIPLES
Principles of food preservation
Overview of fruit and vegetable processing techniques
Summary of small-scale fruit and vegetable processing techniques
Processing pre-treatments for fruit and vegetables
Description of processing methods for fruit and vegetables
POST PROCESSING PACKAGING AND STORAGE
HYGIENE AND SAFETY
The second book of around 90 pages covers the detail of producing a whole range of products as listed below from the table of contents:
Processing outline for dried fruit and vegetable
Processing outline for Jam and Jelly
Fruit jam or jelly – process details and quality
Carrot and lemon jam
SAUCES AND CHUTNEYS
Processing outline for sauce and chutney
Sauce and chutney – process details and quality assurance
Italian style tomato sauce
Italian style tomato sauce
Tomato sauce or ketchup
Tomato puree or simple concentrate
Tomato concentrate (non-cook method)
Coriander chutney (chatni gashnizeh)
Tomato chutney (Chatni Badenjani Romi)
Chili chutney (Chatni Morchi Sorkh/Sabz )
Processing outline for lactic acid fermented pickles (atchar)
Fermented pickles – process details and quality assurance
Process outline for fruit and vinegar
Fruit vinegar – quality assurance and processing notes
If you have any interest in processing vegetables and fruit, these books are really highly recommended.
This document, from US Agriculture, is a review of dehydration at a somewhat higher technology level than is often the case on this blog.
The technologies described include batch cabinet dryer, spray dryer and even the freeze dryer. The article also covers business, marketing and regulatory issues and has many link, unfortunately to mainly Amercan information.
There is an interesting reference to “solar drying” by which they mean drying in the open or what this Blog (and many technologists) terms sun drying. It again raises, this time for a food regulation point of view, the possible contamination of food dried in the open.
…could not determine how California producers can legally sun-dry in the open or why no one in the health department has “picked up on it yet.” A possible explanation is that existing businesses are sometimes “grandfathered in” when new, tighter restrictions are published.
I would by the way note that I have not yet managed to get a reply to by query to California Sun Dry about this issue.
I would have liked to have seen a bit more on the heat sensitive components of the three Amaranthus varieties used as feed and some mass balances to compare the degree of drying with the nutrient changes.
It is also interesting to note that AJFAND is a free online journal and that is edited by Professor Ruth Oniang’o. A few of the other articles that caught my eye were.
Use of dried kapenta (Limnothrissa miodon and Stolothrissa tanganicae) and other products based on wholde fish for complementing maize-based diets. Anna Haug et al.
Production of protein concentrate and isolate from cashew (Anacardium occidentale L.) nut. Semiu Ogunwolu et al.
This uninspiring cover hides the value of the information and misleads on it breadth – it covers processing and business issues in 16 pages of concise and clear information.
The information covers post harvest handling, quality, hygiene, drying, heat treatment, concentration, pulping and pasting. It includes a very interesting process for the large scale production of paste using muslin bag filtration.