Lemon juice for jam making: bottled or fresh?
I bought another preserving book over the weekend (Put 'Em Up! by Sherri Brooks Vinton) and she is adamant about using bottled lemon juice for the consistent acid level. However, the Ball Blue Book specifies when bottled lemon juice should be used (typically for tomato recipes) and just says "lemon juice" for other recipes. I made peach jam last week using fresh lemon juice (I don't keep bottled on hand and haven't for years). I assume I should, nonetheless, be pretty safe from botulism. Your thoughts?
I wouldn't worry about the botulism issue; follow the recipe recommendations and you'll be fine. Most jam fruits are high acid (with the exception of figs) and don't need the ph level lowered but do need the fresh lemon juice in the jam to set. When canning lower acid tomatoes or salsas, with low acid veggies in them, you need a standardized acid, such as bottled lemon juice to lower the ph, to be safe. The Ball Blue Book's and the cookbook author's bottled lemon juice recommendations are covering all the safe bases for acidulating tomato products. Unless you're using a sweet, low or no acid lemon variety, like Meyer or a Mediterrean cultivar, for fresh juice, (which you should not do) just use what the recipe recommends; bottled or fresh when recommended. Even high acid lemon varieties can vary in acid level; bottled lemon juice has standarized acidity; that's why canning tomato products calls for bottled lemon juice, while jams can use bottled, fresh or another acid.
You can also use citric acid (sour salt in the Kosher aisle) in small quantities or Fruit-Fresh in the same quantity as the lemon juice in jam recipes, which is a "natural" mix of citric and ascorbic acid with "other" ingredients, dextrose, etc. and prevents fruit, apples, pears, peaches, etc., from browning, if you have any lingering concerns. I have a recipe for peach jam that calls for either bottled or fresh lemon juice or Fruit-Fresh. Food grade ascorbic acid (vitamin C) is fine also, as Fruit-Fresh is not cheap. Sometimes using other types of acids, like malic or tartaric, or a combination, will allow you to get away from having some of the more delicate jams taste overwhelmingly of lemon, but that's for when you become a canning pro. Here's a handy acid substitution chart:
4 Tablespoons vinegar=
2 Tablespoons bottled lemon juice=
1/2 teaspoon citric acid
Note: Vinegar is not recommmended for canning tomato or salsa products.
I don't like using bottled lemon juice for anything, but when the canning procedure calls for it, I use it. It's recommended by Ball and the National Center for Food Preservation. Bottled lemon juice is also pasteurized and creates no emzymatic action, which is something you want to halt when canning; another reason for using it when recommended.
I do use frozen juice sometimes when lemons are pricy and I need a quantity of it for baking projects. Minute Maid produces it. I don't remember if it contains a preservative; I don't think so, just fresh frozen juice. Useful when larger quantities of lemon juice are needed for canning projects calling for fresh juice, instead of squeezing.
Too bad the Ball Company doesn't have a canning hotline, but I suspect they're wiser in not doing so; can you imagine the volume of calls during canning season?? 20x over the infamous Butterball Thanksgiving Turkey hotline.
Hope this has been helpful without beng an overload of info.